Dolichos bean, which is an important pulse crop, is found infested by a number of insect pests.
Among the insects that infest the plant, lepidopterous and dipterous pod borers are of considerable importance. The insect pests so far recorded on dolichos are:
Aphis medicagensis, Aphis craccivora and Macrosiphum pisi.
Are insects with soft body, tiny, 1-2 cm long, black to greenish in colour. They suck the sap, causing curling, thickening, yellowing and finally drying of the leaves and devitalise the plant. Attacked fruits and flowers do not show further development. Spraying of pyrethrum at 1:800 dilution or nicotine sulphate as 1: 600 or 0.1% lindane or parathion 0.25% is recommended to control the aphids. If fruit formation had not taken place, spraying with BHC 50% wettable powder at 2 gm in one litre of water or malathion 50% at 3 ml in 5 liters of water may be done. Pods treated with malathion should not be harvested or consumed for about a week.
Adisura atkinsoni, Heliothis odsolate and Etiella zinckenella: There are three different species of pod borers, out of which Adisura atkinsoni is a common one on Dolichos lablab. Cold weather is congenial for its development when the field beans suffer considerable damage. The larvae make holes in the pods and damage the crop. Spraying DDT or Pyrethrum is recommended. If the pest occurs just at the time of fruit formation, DDT 50% wettable powder at 1 kg in 300 liters of water can be sprayed. Hand picking of the caterpillars in early stage of attack helps in reducing the intensity of the infestation ploughing the fields after harvest of the crop would expose the pupae which would be destroyed by birds.
Lablab bug, Coptosoma cribraria:
It is a small, oval shaped stick bug. Both the adults and nymphs in large numbers suck sap causing fading and drying of the leaves and vines. It is usually observed on beans. Dusting DDT or spraying 50% DDT wettable powder at 1 kg in 300 liters of water is found to control the bugs.
Mites, Eutetranychus orientalis L. is among various pests infesting Dolichos bean and causing considerable losses. Spraying the crop with 0.05% dicofol or 0.05% monocrotophos or 0.05% quinolphos was most effective.
This paper deals collectively with Adisura atkinsoni, Moore, Heliothis armigera [Helicoverpa armigera], Hb. (Chloridea obsoleta, F.), Maruca testulalis [Maruca vitrata], Geyer, Sphenarches coffer, Zell., and Exelastis atomosa, Wlsm., all of which do serious damage to avare [Dolichos] in Mysore. The females of all these moths lay their eggs singly on the pods, flowers and buds, beginning in late October. The larvae feed on the pods and later bore into them and feed vigorously on the seeds, developing rapidly. When full-fed the majority pupate about 2 inches below the surface of the soil but some on the flower spikes. The borers are most active from mid-December to late January. Larvae of the last generation pupate in the soil, where they remain until the following October. A solution of bleaching powder (1 lb. powder to 8 gals. water) uniformly applied with a hand-syringe to newly-opened flowers and young pods as early as possible in the season, and repeated 2-3 times at fortnightly intervals on flowers and pods developing later, costs little and effectively repels the adults until the pods have become too old to be attractive for egg laying. By harvest time, the colour is again normal. Infestation increased much more slowly throughout the season on treated than on untreated plots, rising from a uniform 5 per cent to 33 and 88 per cent, respectively. The weight of the crop and net profit were increased by nearly 75 per cent.
Wilt of Dolichos bean (Dolichos lablab) in the Sudan Gezira appeared to be due primarily to cockchafer grubs (Schizonycha sp.)
In the soil attacking the hypocotyls or roots of plants upto about 6 weeks after sowing. Many wilted plants also showed symptoms of ashy stem blight (Macrophomina phasioli). But in these, the fungus was probably a secondary invader through rotting roots weakened or damaged by unfavorable soil conditions or insects. Wilt was often severe in Dolichos sown on land cropped to sorghum in the preceding season and sorghum roots harbouring the grubs. Under moderate grubs attack, seed dressings containing organomercurial and BHC gave satisfactory protection at 0.089% BHC/seed, but inadequate when wilt was severe. Dieldrin and aldrin at 0.44 or 0.089% / seed gave excellent protection in all experiments; but their performance under exceptionally severe wilt conditions has yet to be tested, as also the relative efficacies of seed treatment and soil treatment under such conditions. Fungicide-insecticide treatment also reduced pre-emergence rotting of germinating seeds due to grub attack.
Wilt rarely occurred in Dolichos planted on land fallow in the preceding season, but even in the apparent absence of wilt, seed treatment often appreciably improved emergence, plant populations, growth and yields. These effects possibly resulted from control of root damage by soil insects, such damage reducing growth and yields but not sufficiently severe to cause wilting. Pending further investigation, a powder seed dressing containing organomercurial plus 20% dieldrin, (and applied at 1: 450 by weight to seed about 5-6 g/ acre of dieldrin) is recommended for Dolichos bean in Gezira.
Seventeen varieties representing two shades of flower colour, eight shades of seed coat colour and varying maturity periods were taken up for assessing loss in seed yield due to pod borers. At the time of harvest, five samples of 20 pods each were taken at random from each variety. Observations were made on number and weight of seeds that were affected and unaffected by pod borers and the percentage of incidence was worked out. Results were statistically analysed. The mean percentage infestation of the pod borers for all the varieties was found to be 20.19 and the maximum incidence was recorded on the variety M.S. 9497.
The mean percentage infestation of the pod borers for all the varieties was found to be 20.19 and the maximum incidence was recorded on the variety M.S. 9497. The actual loss in seed yield due to borers was maximum in M.S. 9508 with an overall average of 16.40%. When the extent of damage was assessed on seed basis, the loss in seed weight was the highest in the case of PLS. 127, the average being 78.2% for all the varieties. It was interesting that the variety DL.3196 recorded the lowest infestation and damage to the seeds in all the cases. The differences noticed among the varieties in these respects were statistically significant to a high probability level. The infestation of the borers and the actual loss caused by them were found to have strong correlations individually with the age of the plants at flowering. Earliness of the variety (early flowering) was found to be correlated with the resistance of the species. The variety DL.3196 has exhibited remarkable degree of resistance and recorded very low incidence of pod borers. Obviously, this variety does not seem to be palatable to the pod borers owing to the early lignification of the pods, while the medium or late flowering varieties in the flowering and pod setting stage would attract large number of borers. The degree of susceptibility is not so distinct between medium and late duration varieties as between early and medium or late duration varieties. As an exception, one late variety DL.2224 recorded lower pest incidence on par with DL. 3196. But the extent of damage is more or less similar as in the case of medium or late varieties. In view of the earliness of the variety DL.3196, it is likely that it must have either evaded or escaped from the peak period of infestation, thus exhibiting only pseudo- resistance per se.
Melanagromyza bonavistae sp.n. is described from the pods of bonavist beans (Dolichos lablab) and cow peas (Vigna unguiculata) at Kawanda, Uganda. The third instar larva and posterior spiracles are illustrated. Notes on the life-history are also given; two species of primary parasites and one, possibly two, species of hyperparasites have been reared.
Grubs of a Chrysomelid beetle Sagra femorata Durray were found extensively damaging the country bean plants (Dolichos lablab) during July-August, 1972 at the Horticultural Experimental farm, Bangalore of the Indian Institute of Horticultural Research. The grubs feed on the internal tissues of the stem and form galls at the site of feeding. The infected branches wilt and die. Several galls were found on each plant, each gall containing 3-4 grubs. Practically, all the bean plants cultivated over 0.25 ha area were damaged by the pest. Adults were metallic-green and measure 2.4 to 2.6 mm in length and 0.95 to 1.05 mm in breadth. Eggs are laid on the stem. The larvae, after hatching, enter the stem and feed on the internal tissues without migrating to the adjacent stem portions. The full-grown grubs pupate within the stem in oval straw coloured cocoons made from chewed stem wood. Pupal stage lasts for 5-6 months. The pest has only one generation in a year. Damage was earlier reported on country bean due to Sagra nigrita Oliver. The adults of S. nigrita are blue-black and are smaller in size than that of Sagra femorata which is new pest recorded now.
The larvae of Adisura atkinsoni are particularly troublesome. But this pest is controlled by a strain HE-111 of Bacillus cereus var. thuringiensis. In addition, the green catepillar Heliothis armigera, the plume moth Exelastis atomosa and the spotted pod borer, Maruca testulalis are of considerable economic interest.
In Malawi, the flowers are attacked by Mylabris beetles and in Puerto Rico, the bean leaf beetle Ceretoma ruficormis is a major pest. In the Sudan, Cock-shaver larvae, Schizonycha species are important. The use of mercurized seed-dressings has been recommended as an effective control. Mature seeds of the hyacinth bean are susceptible to store pests, particularly bruchid beetles, Callosobruchus species that also attack the crop in the field.
The insect fauna of field bean in Bangalore area of Karnataka was studied, for the incidence and distribution of major insects during 1972 and 1973. During this study, 56 species of insects and a species of mite coming under 8 orders and 22 families were recorded on field bean. Among these 27 species have been recorded for the first time on the crop. Of the insects noticed on field bean, Six species, namely, Aphis craccivora, Cosmolyce boeticus, Adisura atkinsoni, Heliothis armigera, Sphenarches caffer and Etiella zinckenella were common.
Studies on the relative abundance of pod-borers and distribution patterns of the dominant borers, Adisura atkinsoni Moore were conducted at Bangalore with a view to develop a field screening procedure in the fieldbean, Lablab niger to pod borers. Nine species of borers constituted the borer complex on Lablab niger. The borers population peaked in October.
Eggs and early instar larvae of Adisura followed a clumped distribution pattern. Older larvae, however, were distributed uniformly in the field. Adisura moths preferred to lay eggs between 50.8 and 61.5 cm on the erect type of L. niger and between 101.6 and 114.3 cm on the creeping type of the plant. Plant height had a significant positive correlation with the maximum number of Adisura eggs, but upto nearly 115 cm Adisura eggs peaked in number during October, while larvae did so during November- December. Observations on spatial and temporal distribution patterns of Adisura suggest the following:
- Need for a survey of the field before sampling blooms for field screening, as eggs and early instar larvae follow a clumped distribution pattern;
- Blooms between 101.6 and 114.3 cm in the creeping type should be preferably observed in October for screening to ovipositional response;
- Lablab niger cultivars to be tested for larval boring should be observed during November- December.
Chakravarthy and Lingappa compared some parameters to evaluate Dolichos bean germplasms to pod borer, A.Atkinsoni damage as selection of appropriate parameters for screening germplasm to insect damage was basic and important in the development of insect resistant varieties and showed that there is no correlation between pod damage and seed damage.
Singh et al. (1985) has reported a new species of Acanthoscelides udaqamandalensis (L.) from the green pods of field bean ( Dolichos lablab) in farmers fields of Tamil Nadu.
Oviposition and larval feeding habits of the pea blue, Lampides boeticus L. on the lablab bean, Dolichos lablab L. were studied in the field and laboratory. In the field, most of the eggs were laid on the young flower buds in an apical position in the order of inflorescence, but few on the undeveloped flower buds, open flowers, pods, leaves, and stems. The 1st- and 2nd-instar larvae were found mainly in young flower buds, whereas the 3rd- and 4th-instar larvae were found in flowers or pods. The 1st- and 2nd-instar larvae attacked exclusively the anthers of flower buds. This characteristic feeding habit was also demonstrated by a laboratory test, i.e. the newly-hatched larvae inoculated on young flower buds penetrated within 24hr into the distal part of the flower buds where the anthers were located, and consumed them selectively. Larvae inoculated on the pods were not successful in penetrating into them and they died or dispersed.
Fieldbean, which is an important pulse crop, is found infested by a number of insect pests.
Diversified types of L. niger var. lignosus and L. niger var. typicus were screened for their reaction to pod borers (larval boring and ovipositional response) in the field from 1975 to1977 at the Agriculture College farm, Bangalore. During January-February 1975, a preliminary screening of 62 cultivars of spreading type (L. niger var. typicus) was done. Fortnightly observations on the per cent of buds, flowers and pods damaged and the number of eggs laid on these plant parts was recorded on randomly selected inflorescences in each cultivar commencing from the first week of January 1975. Since there was variation in the maturity of the cultivars, three observations were made during blooming period.
During 1975 - 76, cultivars were screened, which included 49 lines from the previous screening trial. Procedure followed was the same as before except the first observation starting 3 weeks earlier as the pest activity was high during December and early maturing lines were in bloom. The promising lines from the earlier screening tests were retested during 1976-77 along with 20 new entries. In all there were 83 cultivars which included both field (var. lignosus) and garden types (var. typicus). The borders of the experimental plots were sown with the local susceptible cultivars. Three monthly observations were recorded commencing from October 15, 1976. Cultivars with 0-20 % pods bored in all the three field trials were scored as resistant; 20-60% as susceptible and more than 60% as highly susceptible.
Similarly, a cultivar was regarded as non-preferred for oviposition if it had upto 10 eggs per 10 inflorescences in all the three trials as against 11-60 in preferred and more than 60 in highly preferred lines.
Confirmatory studies on larval boring and ovipositional response were made under artificial infestation conditions in the field. Adisura atkinsoni, the dominant borer species in the field on local cultivars during August-February, was used as the test insect. More than 95% of the farmers in Karnataka grow local variety, which is photosensitive and blooms from August to February.
Field screening of germplasm for 3 years led to the isolation of two cultivars, PLS-24 and PLS-16-1, which had consistently displayed resistant reaction response both for larval boring and for laying eggs. Preliminary tests indicated pod colour, pubescence and fragrance seemed to have been associated with resistant responses. However, none of these three characters per se imparted resistance. In other words, it appeared to be a combined effect of all the three characters. Pod wall did not form a physical barrier. Positive relationship was noticed between the amount of chloroplast and susceptibility. Anthocyanin pigment in the pod wall was associated with resistance.
Based on the field and laboratory evaluation of the Lablab cultivars to the bean aphid, Aphis craccivora, the local and H.2 cultivar were rated as highly susceptible. Those two cultivars, PLS-24 and PLS-16-1, which showed resistance to borers, were highly susceptible to the aphid infestation.
Under artificial infestation conditions, the resistant cultivars exhibited susceptibility to Adisura attack, but conferred resistance to ovipositional response.
Factors responsible for host preferences for larvae and adult insects were different and independent. PLS-24 and PLS-16-1 contained significant degree of antibiosis as demonstrated by reduced larval survival, larval and pupal weights, prolonged larval duration and altered sex ratio.
Cultivars that sustained low levels of seed yield loss under high infestation conditions were identified as tolerant. MS-9579 and IC-661-1 exhibited low levels of tolerance. Resistant cultivars proved non-tolerant even to slight infestation (ca 10%) received under field conditions.
Birds may prevent the build-up of the pests and thus contribute to the pest management programmes. They assume greater significance in subsistence mixed- farming systems involving fieldbean where sophisisticated pest control methods are not always possible. The house crow Corvus splendens, appeared the most important predator and its feeding rate (4± 0.2 larvae/min) and number (> 200/km2) at the study sites were higher than other insectivorous birds. Multiple cropping patterns promoted higher predation rates than pure stands. Seed yield loss in field beans was negatively correlated with index of species richness. Seed yields in the site with the highest species index were almost 39 % greater than those in the site with the least number of bird species.
House crow, blackdrongo, mynah, house sparrow and oriole are predators of borer larvae where fieldbeans form a component of multiple cropping systems in Karnataka. The house crow appears to be the main predator of borers and is the predominant species. Reduced seed- yield losses are associated with higher bird and insect species richness. In India, on mixed cropping, subsistence farms such as fieldbeans, bird diversity can be increased by providing insectivorous birds with niches for feeding, shelter and nesting. Supplementing perch sites by bamboo poles (2m height) would facilitate insectivorous activity of birds. Maintaining shrubs/trees along borders of field beans in multiple cropping systems would increase insect diversity compared to monocultures. Reducing insect infestations by combining biological and cultural methods is ecologically desirable and the value of high insect and bird diversity also militates against the use of insecticides.
The efficacy of certain insecticides against Aphis craccivora on cowpea ( Vigna unguiculata) and hyacinth bean ( Lablab purpureus) was assessed in the field in India. Methyl-demeton[demeton-methyl] 0.025% spray was the most effective treatment, followed by 0.04% monocrotophos. Endosulfan at 0.07% was the safest insecticide for the coccinellid predator Menochilus sexmaculatus [Cheilomenes sexmaculata], followed by 0.04% monocrotophos.
Parsi et al. (1989) conducted studies on ovipositional behavior and preference of Callosobruchus phaseoli and its damage in different varieties of field bean and they reported that the eggs were laid singly on seeds and in mass on pods; mature green, semi dried to dried pods were preferred for oviposition. There was no oviposition occurred on pods, flowers and young pods. Seed damage was reported in 139 varieties of field beans after three and half months of storage which ranged from 0.00 to 93.33%. Based on these observations 42 varieties were categorized as highly susceptible, 33 as moderately susceptible, 73 as less susceptible and 1 as resistant.
The distribution pattern and larval behaviour of the major flower and pod borer Lampides boeticus on vegetable lablab were studied in Bangalore, India. The distribution of eggs and bored flower buds were found to be contagious. Most of the flower buds with pinhole damage had small larva (first and second instar) inside them. Flower buds with medium damage had medium larva (third instar). The flower buds and pods with large damage very rarely harboured larva. The medium and large larvae migrated and caused damage to flower buds and pods. Use of larval behaviour in developing a suitable pest management programme is indicated.
In this study for the chemical control of C. theobromae in field bean under field conditions, nine insecticides were applied only once when the pods turned yellow colour. Based on the observations 20 days after spraying on the per cent holed pods, the minimum pod damaged was 20.3 per cent when sprayed with Quinolphos and the maximum of 36.6 per cent was reported with the spray of Monocrotophos, followed by 31.6, 31.2, 29.0, 29.0, 26.1, 23.8 and 22.2 per cent in case of Dimethoate, Chloropyriphos, Fenvalerate, Methyl parathion, Endosulfan and Malathion, respectively. None of the insecticides were able to prevent the field infestation completely. Study indicated that local variety of field bean was highly susceptible, HA-3 and maniavare were moderately susceptible and Sel-1 and Sel-2 were least susceptible on the basis of growth index studies.
Egyptian bean belongs to legumes with high protein content in the seed. Young pod and straw are valuable source of feed and food. Seed of Egyptian bean can also be used to substitute soybean in making soy products. It is also excellent to be used as green manure, and effective for erosion control and soil protection. Protein content of varieties DL 10, DL 55 and Local Muneng ranged from 22 to 23 percent, and their yield ranged from 0.7 to 1.0 t/ha. They can be cultivated in Sumbawa, NTT and East Timor. Pod borer, caterpillar, powdery mildew, leaf spot and rust are the pests and diseases possible to be the constraints when growing Egyptian bean.
Eleven Dolichos lablab cultivars showing different reactions to Aphis craccivora were cultivated for study of predator with interaction. The Coccinellid Coccinella septempunetata was the predominant predator-pray of A. craccivora on D. lablab in the experiment conducted during the khariff (monsoon) season of 1991-92 at Kalyanpur, U.P. The maximum predator population of 3.91 per plant was observed during March, although the A. craccivora population declined during the same period. However, when the A. craccivora population peaked during the 2nd week of December (77.22/plant), an increase in the predator population subsequently followed. There was a negative correlation between the average prey and predator population.
Studies on the biology of Aphis craccivora at 20±1°C, 50% RH and LD 16.8 h revealed the presence of 4 instars. The nymphal period on cowpea (Vigna unguiculata), Lablab (Lablab niger) and pigeon pea (Cajanus cajan) was completed in 13-16, 13-16 and 14-16 days in the vegetative stage and 12-13, 13-15 and 13-14 days in the flowering stage, respectively. Adult longevity in the flowering stage (15.8-17.1 days) was shorter than in the vegetative stage (18.9-20.3 days). A similar trend was observed with respect to total lifespan, which was 29.1-30.6 days in the flowering stage and 33.6 - 33.9 days in the vegetative stage. Shortest adult longevity, the longest nymphal period and lowest foecundity were observed on Lablab. Pigeon pea was the least preferred host plant. The highest foecundity, adult longevity and reproductive rate of A. craccivora, when reared on cowpea led to its selection as the most favourable host for aphid multiplication in the laboratory. A cage was devised which could be utilized for studying the biological parameters of A. craccivora on different host plants.
Losses caused by the Lablab bug Coptosoma cribrasia (Megacopta cribrasia) (Fabricius) were estimated under greenhouse conditions on field beans (Lablab purpureus var. lignosus). Percentage reduction in seed yield was lowest at 0, 6, 10 and 20 insects per plant and highest (44.22) in treatments which received 160 insects per plant. Studies also showed that infestation at the early crop stage resulted in a greater seed yield loss (21.33%). Seeds taken from plants with high infestation levels were smaller than those taken from plants with no or low levels of infestation.
The field bean evaluation was made at the Vegetable Experimental Research Farm, Batkee, JNKVV, Jabalpur in a randomized block design with three replications.
Different growth parameters of varieties did not seem to influence the pod damage in fieldbean. However, short duration varieties (239 days), viz., JDL 53 and Rajani had least pod damage (10.5 and 10.1%), respectively. Rajani was higher yielder and also short duration. Variety DL-3196 was least susceptible to pod borer. The variety JDL-79, inspite of having higher pod infestation gave the highest yield.
The life history of four types of progenies of the black bean aphid, Aphis craccivora, comprising apterous progeny from apterous virgins, progeny from alate virgins, alate progeny from alate virgins and alate progeny from apterous virgins was studied in the laboratory on Dolichos lablab at maximum temperature 30°C, minimum temperature 16°C and relative humidity 71%. Almost all stages of the life history of the progenies are extremely viable and statistically significant. The total nymphal period was the lowest (5.20±0.79 days) in apterous progeny from apterous virgins and highest (6.64 ± 0.35 days) in alate progeny from alate virgins.
Among the pod borers of pulse crops, L. boeticus was recorded for the first time as a pest of pea and pigeon pea from Manipur, India, with an average infestation of 26 and 24.38%, respectively, during November-April 1999-2000. In addition to these host plants, the infestation of this pest was also newly recorded on different leguminous crops such as Vicia faba, Vigna sinensis [Vigna unguiculata], Dolichos lablab [Lablab purpureus], Canavalia ensiformis, Vigna unguiculata and Phaseolus vulgaris.
The susceptibility of 20 L. purpureus inbred lines to defoliators, aphids and jassids was evaluated in Jhansi, Uttarpradesh, during Kharif season of 2002. Leaf damage by defoliators ranged from 22.90 to 59.70%. The lowest leaf damage due to Pagria signata (Colposcelis signeta), Plusia nigrisigna (Antographa nigrisigna), and Hieroglyphus nigrorepletus infestation was observed in AC-120 (92.9%), whereas the greatest damage was recorded for AC-227 (59.70%). Other lines which showed less infestation were AC-351 (22.9%), AC-212 (30.63%) and LPS-2 (31.10%). The number of jassids (Empoasca kerri) per leaf ranged from 2.56 (AC-120) to 4.44 (AC-151). Lower E. kerri density was also observed in AC-351 (2.67), AC-212 (3.11), AC-232 (3.22), S-27 (3.22) and JLP-3(3.22). The number of aphids (Aphis craccivora) varied from 94.0 (AC-120) to 1641.0 (S.27). A craccivora population was also lower in AC- 134 (125.7), AC-351 (125.0) and AC-354 (128.3).
A survey was conducted to determine the presence of insect pests in field bean (Dolichos lablab [Lablab purpureus]) plantations, Yavatmal, Maharashtra, India, and to evaluate new genotypes (i.e. Konkanbhushan, AKW 9301, AKW 9303, AKW 9304, AKW 9305, AKW 9306, AKW 9311 and AKW 9312) for tolerance to pod borers under field conditions. The field bean raised in September was almost free from pests for a month but was later infested by Colemania sphenariodies [Colemania sphenarioides], Cosmopteryx phaeogastra [Cosmopterix phaeogastra], Hedylepta indicata [Omiodes indicata], Euproctis subnotata, Empoasca spp., Aphis craccivora, Megalurothrips usitatus, Sphenarches anisodactylus, Adisura atkinsoni, Helicoverpa armigera, Maruca testulalis [Maruca vitrata], Riptortus linearis and Nezara viridula. Konkanbhushan recorded least infestation followed by AKW 9303, AKW 9304 and AKW 9301. On the other hand, AKW 9306, AKW 9303, AKW 9311 and AKW 9312 had significantly high infestation than Konkanbhushan.
In this study, development of C. theobromae on the seeds and pods of Dolichos under field conditions was studied. After passing the winter as hibernated larvae, adults emerged during March and April. Amorous males impregnated the females among the seed and pods of the host plant. Eggs laid on seeds and pods developed into first instar larvae, which penetrated the seeds of host plant. Remaining part of the life cycle was completed inside the host seed and adults came out by cutting a circular window in the testa of the host seed. Six to seven overlapping generations were recorded between April to October. The life cycle was completed in 28.9±1.72 days.
The activity of pod borers occurred throughout the cropping period after pod formation stage. The pod damage was highest in August-sown crop than on September-sown crop. Among the natural enemies of pod borers, the parasitoid Bracon sp. Greeni (Ashmed) caused 10-20 per cent parasitization. The important predators included ladybird beetles, green lace wing arid robber fly.
The economic injury level for pod borers was determined at 0.45 larva per plant. A minimum pod yield of 3.89 q/ha was recorded in untreated control, while as high as 13.0 q/ha yield could be obtained from completely protected plots. On the basis of IBC ratio, the treatment with 3 sprays of fenavalerate was the best (6.69), followed by 2 and 4 sprays (5.71).
Among the indigenous materials, application of GCK+ cow urine resulted in maximum yield of 8. 01 q/ha followed by GCK (7.91 q/ha) and NSKE + cow urine (7.8 q/ha). The highest IBC ratio of 3.01 was observed in GCK+ cow urine followed by GCK (2.95), GE+ cow urine (2.81) and NSKE+ cow urine (2.65).
Among the newer molecules, maximum pod yield (15.14q/ha) was obtained from plots treated with emamectin benzoate followed by spinosad (14.11 q/ha) and indoxacarb (13.11 q/ha). However, the indoxacarb application resulted in highest IBC ratio (6.35), followed by fenvalerate (6.15).
Studies were conducted to find out the resistant lines in field bean to pod borers viz., Helicoverpa armigera and Adisura atkinsoni and bruchid Callosobruchus chinensis. 133 germplasms lines were screened for two years in 2004 and 2005. The mean of two years indicated that the infestation of Helicoverpa armigera ranged from 0 to 29%. 15 genotypes viz., GL 69, 82, 89, 93, 24, 1, 117, 86,96, 121, 61, 413, 412, 135 and 123 recorded less than 10% infestation. The infestation of Adisura atkinsoni ranged from 0 to 17 per cent. 132 genotypes showed 0 - 10 % infestation indicating the row infestation of insect. Callosobruchus chinensis infestation ranged from 0 -50%. 92 genotypes showed 0 -10% infestation.
Studies on population dynamics of field bean revealed that, during the study period 22 species of insect pests were recorded on field bean. Population build up of pod borers noticed from May II fortnight to February I fortnight with peak during the II fortnight of November. The pod borers population exhibited significant negative correlation with minimum temperature and non-significant negative correlation with maximum temperature and relative humidity. However, it was nonsignificant positive correlation with total rainfall. Among sucking pests Aphis craccivora Koch, leaf hoppers, thrips, Riptortus pedestris F., Riptortus strennus Horvarth, Coptosoma cribraria F, Anoplocnemis phasiana F. and Nezara viridula L. were more predominant. Defoliators like Spilactia obliqua Walker and grass hoppers were also observed but in less numbers. The natural enemies recorded included Campoletis chlorideae Uchida, Bracon sp.
A field experiment was conducted at B.A. College of Agriculture, AAU, Anand during kharif 2003. Results revealed that after first spray, significantly least (12.32 aphids/twigs) incidence of A. craccivora was observed in plots treated with Neem Seed Kernel Extract (NSKE) @ 5 % than other botanicals, However, highest population of pest was found in Vanguard (21.62), followed by Gronim (17.39). Plots treated with NLE, Naffatia Leaf Extract (NFLE) (Ipomoea fistulosa), Neem Azal-F and Neemolin plus exhibited more or less same level (14.36 to 16.08) of aphid incidence. Results of second spray also revealed that NSKE was found to be superior treatment against aphids, followed by NLE, Gronim and NFLE. The treatments of NSKE (5%) and NLE (10 %) were found to be significantly promising in suppressing the leafhopper population over other botanical insecticides.
The incidence of Helicoverpa armigera was observed least (25.41%) to green pods in NSKE treated plots. NLE and Gronim ranked next to NSKE by registering 29.68 to 31.41 per cent pod damage and differed significantly from rest of the treatments except Econeem. Plots sprayed with NSKE yielded maximum (2913.81 kg/ha) green pods, followed by NLE (2681.11 kg/ha) and Gronim (2543.21 kg/ha) and these three treatments were significantly superior to rest of the treatments. The highest incremental cost benefit ratio (ICBR) was obtained in case of NLE (1: 27.06), followed by NSKE (1: 21.35), Gronim (1:16.10) and NFLE (1:10.34).
A study was made on the seasonal incidence of pod borer complex of Dolichos bean. A total of 8 different pod borer species have been recoded on the crop at Bengaluru condition. The pod borer complex included Helicoverpa armigera, Maruca testulalis, Lampides boeticus, Exelastis atomosa, Sphenarches caffer, Adisura atkinsoni, Callosobruchus chinensis and Etiella zinckenella.
The incidence of H. armigera was observed throughout the cropping period with a total incidence of 9-161 larvae per 4 quadrates. The peak incidence (40.25 larvae per quadrate) was recorded during 16th November, 2008. The peak incidence of M. testulalis. was observed during first week of December, 2008 with a mean incidence of 17 larvae per quadrate. The activity of A. atkinsoni observed from first week of November, 2008 to third week of January, 2009 and peak incidence (21 larvae per quadrate) was observed during last week of December, 2008. The incidence of S. caffer started from first week of December, 2008. The incidence of S.caffer started from first week of observation (29th September, 2008) and reached peak (16 larvae per quadrate) during 16th November 2008. The peak incidence of remaining pod borers viz., L. boeticus (15 larvae per quadrate), E. atomosa (17.75 larvae per quadrate),C. chinensis (12.25 adults per quadrate) and E. zinckenella (15.75 larvae per quadrate) were observed during 21st December, 23rd November, 7th December and 7th December, 2008, respectively.
Helicoverpa armigera was emerged as most abundant pod borer species throughout the cropping season with per cent incidence range of 17 to 71. The per cent incidence was as high as 71.05 during last week of September and it maintained dominance with 66.41, 63.30, 62.50, 50.24, 52.79, 43.79, 39.95, 32.41, 27.85, 25.16, 24.89 and 20.80 per cent incidence in subsequent observation weeks. Remaining pod borers observed with low incidence percentage.
The newer molecules were in general superior over the conventional insecticides as well as the indigenous materials. Flubendiamide24%+ Thiacloprid 24-48% recorded very high larval reduction of 79.09 and 79.42 per cent after first and second spray, respectively. The next to follow were emamectin benzoate (73.59 and 74.02%). The treatments recorded lower pod and seed damage (13.13, 15.09, 15.81, 15.55% and 18.41, 21.20., 22.45% respectively).
The maximum pod yield (16.35 q/ha) could be obtained from the plots treated with Flubendiamide24% + Thiacloprid 24-48% followed by emamectin benzoate (14.994 q/ha), indoxacarb (14.57 q/ha) and flubendiamide (11.87 q/ha). However, the fenvalerate application resulted in highest BC ratio (13.26) followed by indoxacarb (8.91). Studies on screening of 50 germplasm lines Dolichos bean revealed two germplasm as resistant, one line as moderately resistant, three lines as tolerant, nine lines as susceptible and 35 lines were proved to be highly susceptible with respect to resistance to larval boring. Among the lines screened, the least pod borer damage to pods (3.34%) was recorded in GL 248 followed by GL 45 (7.81%) and GL 133 (111.28%) and highest pod damage recorded in local cultivar (65.87%).
Studies on non preference to oviposition revealed 2 cultivars to be non- preferredm 2 cultivars to be less preferred, 44 cultivars to be preferred and 2 cultivars to be highly preferred for oviposition. Among the non preferred cultivarts, GL 248 and GL 45 received least number of eggs, 1.36 and 5.28 respectively.
Fifty Dolichos entries were grown in the field to find out the resistant entry to pulse beetle C. theobromae attack. The percent pod infestation was ranged from 0.06 to 39.98%. The study revealed that, the entry GL 187 had recorded least percent pod damage (0.06) among the 50 entries followed GL 60 (0.92%),where as the entry GL 37 recorded highest percent pod infestation (39.98%), followed by GL 83 (32.73%).
Among the different pod and seed characters pod shape, seed shape and seed colour were positively influence the pod infestation. However all the seed and pod characters influence the pod infestation up to 45 per cent. Fresh seeds of the same 50 entries were stored in laboratory to find out the field infestation of this pest. After 3 months of storage of seeds, the entry GL 187 had recorded 19 per cent seed damage followed by GL 60 and GL 128. GL 139 had recorded highest percent seed damage (97), followed Local variety (96%). Investigations on the relative susceptibility of different entries of field bean carried out in the laboratory conditions. Sixteen entries were selected which are shown good response to our aim of the study under field conditions. Out of these sixteen entries GL 187 was least preferred for egg laying (76eggs), where as most preferred in GL 139. GL 49 recorded least per cent seeds with eggs as compared to Local variety, which has recorded highest per cent seeds with eggs. Least adult emergence, least percent damaged seeds (71), highest
Trials were carried out to control the field infestation of dolichos by bruchid Callosobruchus theobromae by spraying insecticides namely Spinosad @ 0.2ml/ltr, Indoxacarb @ 2ml/ltr, Endosulfon @3ml/ltr and Malathion @3ml/ltr with different spray schedule. The study revealed that spraying of Malathion @ 3ml/ltr of two sprays was effective in controlling the field infestation of bruchids and such an insecticidal treatment resulted in preventing the seed damage.
The field experiment was conducted at College of Agriculture, Shimoga during Kharif 2006 to evaluate the efficacy of some newer insecticides against pod borers of field bean Lablab purpureus (L.). Among the treatments spinosad 2.5 SC (1 ml/l) emerged as best treatment which brought about 36.44,27.09 and 29.24 per cent reduction in pod borer populations after first, second and third spray, respectively as well as least pod and seed damage of 14.38 and 10.66 per cent, respectively with maximum yield of 44.02 q per ha followed by thiodicarb 75 WP (1 g/l) which caused 36.68, 29.42 and 17.97 per cent reduction in pod borer population after first, second and third spray, respectively with pod and seed damage of 13.44 and 11.64 per cent, respectively and consequently resulted in higher yield of 43.88 q per ha. Which is on par with spinosasd (1 ml/l) in treated plots minimum yield of 29.96 q per ha was obtained from the plot sprayed with 40 SP methomyl, but was significantly superior to control (untreated). However, highest B: C ratio was recorded in spinosad (2.13) treated plots followed by thiodicarb (1.98).
Sixty eight germplasm accessions screened under natural epiphytic condition for pod borer reaction were classified as resistant, moderately resistant, moderately susceptible, susceptible and highly susceptible based on per cent pods damaged (Table 1). The mean per cent pod damage was 27.92±9.25. Only six out of 68 accessions viz., DA-15, DA-36, DA-39, DA-44, DA-63 and DA-65 were highly resistant with pod borer incidence falling in the range of 0 to 9.42 per cent. These genotypes were early maturing types with days to maturity falling in the range of 91 (DA-63) to 99 (DA-36) days. The moderately resistant accessions were DA-22, DA-40, and DA-53 with pod damage of 9.43 to 18.67 per cent and crop duration of 101 (DA-22) to 107 (DA-53) days. Twenty two germplasms with 18.68 to 27.92 per cent pod damage showed moderately susceptible reaction. High susceptibility with 27.93 to 37.17 per cent pod damage was observed in eight genotypes where in days to maturity ranged from 133 (DA-37) to 145 (DA- 35) days.
The investigations on screening of accessions of field bean, physical characters of pods, seeds and their biochemical constituents for resistance to bruchid,Callosobruchus theobromae L., were conducted at GKVK, University of Agricultural Sciences, Bengaluru during 2009-2010. Forty field bean accessions were grown in the field to find out the resistant entry to pulse beetle C. theobromae infestation. The pod infestation ranged from 1.25 to 36.84 per cent. The entry GL-164 had recorded least pod damage (1.25%) among the 40 accessions followed by GL-78 (2.57%) and these were identified as tolerant accessions. Whereas, the accession HA-4 had recorded highest per cent pod infestation (36.84 %) followed by HA-3 (35.06%) and these were identified as susceptible. Different pod and seed characters like pod shape, seed colour and pod wall thickness was having positive influence on the pod infestation. Tolerant accession GL-164 recorded the lowest protein content (121.6 and 134.4 mg/g), total soluble sugar (18 and 28 mg/per g) highest phenol (7.12 and 8.56 mg/g), tannin (7.1 and 5.2 mg/g) in pod wall and seeds, respectively. Accession HA-4 recorded highest protein content (185.36 and 195.2 mg/g), total soluble sugar (65 and 85 mg/g ) where as lowest phenol (3.87 and 4.22 mg/r g), tannin (2.3 and 1.00 mg/g) in pod wall and seeds, respectively. Pods of GL-164 recorded the highest enzymes activity of peroxidase (3900 units/g) and phenylalanine ammonia lyase (PAL) (168 units/g) whereas pods of HA-4 recorded lowest peroxidase (900 units/g) and (PAL) (87 units/g). The tolerant accessions GL-164, GL-187, GL-63, GL-195 and GL-127 have shown maximum of 2, 3, 5, 3 and 9 bands, respectively while the susceptible ones namely GL-36, GL-46, GL-102 HA-3 and HA-4 have shown a maximum of 11, 10, 9, 11, and 8 bands each. The bands 6 and 7 were commonly present in all the ten accessions.
The studies on the effect of dates of sowing, efficacy of biorationals, biodynamic pesticides and safer insecticides for the management of pod borers in field bean were undertaken during kharif 2009 at the Main Agricultural Research Station (MARS), University of Agricultural Sciences, Dharwad. Results indicated that sowing during third week of July recorded least per cent pod (32.34) and seed damage (41.21) among the different dates of sowing. This was followed by sowing during second week of July.
Among the four species of pod borers attacking the seed,Maruca vitrata was found to be the predominant one followed by Cydia ptychora. However, the population of Helicoverpa armigera and Lampdius boeticus were negligible. The important predators observed during study period were Robber fly, lady bird beetle grub, Sryphids, Chrysoperla carnea Stephens and dragon fly.
Efficacy of Bacillus thuringensis @ 1 g/l and Endosulfan 35 EC @ 2 ml/l were more consistent in bringing down the incidence of pod borers irrespective of the two sprays and highest yield of 20.73 q/ha and 19.77 q/ha respectively. This was closely followed by NSKE @ 5% and Pongamia glabra SE 5% among the different biorationals.
Among different biodynamics, Panchagavya (3%) + NSKE (5%), Panchagavya (3%) + GCK (0.5%0 and Cow urine (10%) + GCK (0.5%) emerged as the best treatments with least per cent pod and seed damage and higher pod yield.
All the newer insecticides except Rynaxiper 10 SC were effective in reducing the incidence of pod borers. However, Novaluron 10 EC (0.1 ml/l) proved to be superior followed by Emamectin benzoate 5 SG @ 0.2 g/l, Spinosad 45 SC @0.1 ml/l and Flubendiamide 20 SC @ 0.2 g/l.
Lablab (Lablab purpureus L) is a multipurpose drought tolerant legume grown by small holder farmers in the semi arid areas of Eastern and Central provinces of Kenya. Cowpea aphid, Aphis craccivora (Koch) , is a pest of lablab which causes 20-35% yield losses. The current methods used to control the pest are either costly for the farmers, detrimental to the environment or not effective especially during heavy infestation. The use of plant host resistance (HPR) to cowpea aphid CPA is a more versatile method owing to its compatibility with other components of integrated pest management and conservation of the environment. Identification of the sources of resistance to the aphids is a prerequisite to a successful breeding programme. The objective of this study was to determine the tolerance of some Kenyan lablab accessions to CPA at various plant growth stages and determine the effects of the aphids on the growth of these accessions. Thirty five accessions were tested for aphid resistance at three different growth stages in a completely randomized design with three replication. Each test plant was artificially infested with four wingless aphids and scoring for plant damage done six weeks later. Results showed that accessions and stage of infestation were significant (p<0.05) for plant damage. None of the accessions tested was resistant (damage score <3.0) to the aphids at any of the stages. Only one, 11 and 13 accessions showed moderate resistance when evaluated at 14, 40 and 70 days after sowing (DAS) respectively. The mean plant damage scores were significantly lower at 40 and 70 DAS compared to 14 DAS suggesting that resistance to CPA increases with plant age. Cowpea aphid infestation on lablab at 14 DAS reduced plant height and shoot weight by over 60% while infestation at 70 DAS reduced number of pods by 20%. This research is an important step towards generation of information for guiding plant breeders searching for resistance genes to CPA fo r crop improvement.
To evaluate the changes in the activities of digestive enzymes activities of silkworm supplemented with Indian bean (Dolichos lablab). Finely powdered Dolichos lablab was dissolved in distilled water and diluted to 2.5 %, 5 %, 7.5 % and 10 % concentrations. Fresh mulberry leaves (Morus alba L.) were sprayed by each concentration and were fed to silkworms, from 3rd to 5th instar, five feedings/day. Group 1 larvae received mulberry leaves sprayed with distilled water and served as control, group 2 larvae received 2.5% Dolichos lablabmulberry leaves, group 3 larvae received 5 % Dolichos lablab sprayed mulberry leaves, group 4 larvae received 7.5 % Dolichos lablab sprayed mulberry leaves and group 5 larvae received 10 % Dolichos lablab sprayed mulberry leaves. Silkworm larvae fed on Morus alba L(mulberry) leaves enriched with 7.5 % concentrations of Dolichos lablab, significantly gained more pupa weight, silk length and silk weight as compared to those fed on normal MR2 mulberry leaves. Hence, 7.5% dose was fixed as an effective dose. Further, same study was conducted to find out the changes in the digestive enzymes activities in the midgut occurred in the fourth day of IVth instar larvae. There was a significant increase in the midgut urease, amylase, sucrase and protease activities. But midgut trehalase activity was significantly decreased. The results suggest that coadministration of Dolichos lablab with mulberry leaves at a concentration of 7.5% has enhanced the digestion of ingested food which in turn reflects in the quantity of silk produced.
Investigations were carried on the seasonal incidence of pod borer complex of Field bean, Lablab purpureus L. (Sweet). Among pod borer complex, Helicoverpa armigera was found predominant pod borer with a peak incidence of 40.25 larvae per 5 plants during third week of November, 2008. Adisura atkinsoni was found next major pod borer with a peak incidence of 21 larvae per 5 plants during December, 2008. A. atkinsoni appears to have changed its life cycle with changed photo-insensitive Lablab cultivars and was observed only during late pod maturing stage. M. testulalis was found minor with peak incidence of 17 larvae per 5 plants during December, 2008.
A study was carried out to investigate the incidence of different insect pests and predators on new variety, HA-4 of dolichos bean. The results of the field study revealed that 15 insect pests belong to nine different families of five orders and five species of predators belonging to five different families coming under four orders. The sucking pest population was found throughout the year. The peak population of aphids (49.00/3 leaves), pentatomid (5.20/5 plants) and coreid bugs (11.20/5 plants) were observed on 60 days after sowing (DAS). Whereas, eurybrachid bugs (5.20/5 plants) recorded at 50 DAS. Among the podborer complex, higher pod damage due to Helicoverpa armigera, Maruca vitrata and Lampides boeticus was 20.43, 16.66 and 10.20 per cent damage, respectively on 80 DAS, whereas Callosobruchus theobromae (12.55 %) was observed on 90 DAS. The important predators viz., robber fly, coccinellids, syrphids, green lacewing and dragonfly were prominent ones. The activity of predators was high between 40 and 60 DAS and population decline was observed thereafter.
Forty field bean accessions were screened against pod borer complex at dry land Farm, S.V. Agricultural College, Tirupati during late Kharif, 2010-11. The accessions screened were grouped into least susceptible, moderately susceptible, susceptible and highly susceptible varieties based on percent pod damage and the yield obtained. The results revealed that the accession, EC-92956 recorded the least pod damage (9.58%) and highest yield of 1.55 kg. The reaction of other accessions to the pod borers' infestation is discussed.
The crude seed extract of neem, black pepper, mahogani, and garlic bulb with three doses were evaluated against legume pod borer in the country bean field in two seasons’ kharif 2006 and rabi 2006-2007. The neem seed extract applied @150 and 100 g/l and mahogani seed extract @ 100 g/l of water 7 days intervals on the country bean showed better performance in the reduction of flower and pod damage with significantly higher yield of bean in both the seasons. The seed extracts lost the efficacy against legume pod borer after 7 days of application.
A total of eight pod borers belonging to eight genera were recorded on field bean in Bengaluru. Among them, Helicoverpa armigera was the predominant pod borer and its incidence was as high as 80.50 larvae per 10 plants during third week of November. The life cycle of Adisura atkinsoni was synchronous with the life cycle of the local photosensitive Lablab cultivars. But currently, Adisura atkinsoni appears to have changed its life cycle and was observed only during late pod maturing stage with a mean of 42 larvae per 10 plants. All the pod borers have shown negative correlation with maximum temperature and rainfall while positive with relative humidity.
The investigation was carried out at the Agriculture Research Station, Balajigapade, Chickaballapura district during kharif season 2009. The evaluated biopesticides were NSKE (5%), HaNPV (250 LE/ha), Bt (1kg/ha), neem oil (2%), Panchagavya (3%), Clerodendron + Cow urine extract (10%) and sequential spray of HaNPV-Bt -NSKE, Bt-NSKE-HaNPV and NSKE-HaNPV-Bt. FYM (9.5 t ha-1) and bio-digester liquid (6,500 l ha-1) were applied to organic plots. Sequential spray of insecticidal spray (Carbaryl-Endosulfan-Malathion) and recommended dose of FYM (7 t ha-1), fertilizer (25:50:25 kg NPK ha-1) were applied to inorganic plot. Pod borers viz., Helicoverpa armigera (Hübner), Maruca testulalis Geyer, Exelastis atomosa Walshinghan, Sphenarches caffer Zeller, Etiella zinkenella (Treitschke), Lampides boeticus Linnaeus, Adisura atkinsoni Moore emerged as serious pests during cropping period. Sequential spray of insecticides carbaryl-endosulfan-malathion applied at 45, 55 and 70 DAG, respectively recorded less insect pests abundance. Among biopesticides, sequential application of NSKE-HaNPV-Bt was effective against insect pests. HaNPV was effective against H. armigera larvae, but ineffective to other pod borers. Panchagavya and clerodendron + cow urine extract were ineffective in reducing the pod borer incidence. Among biopesticides treated plots, sequential application of NSKE-HaNPV-Bt recorded higher grain yield (10.01qha-1) whereas, package of practices followed treatment (inorganic plot) recorded 11.37 qha-1 grain.
A total of eight different pod borer species belonging to eight different genera were recorded on Dolichos beans in Bengaluru. Among the pod borers, Helicoverpa armigera Hubner was found to be the major and its numbers and dominance overwhelmingly prepondered over other species.
Field experiment was conducted in the research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh during 2009 kharif season to evaluate the efficacy of insecticides for increasing yield of country bean by protecting pod damage by bean pod borers. The spray plots gave significantly higher yield than the control plots. Among the insecticides, Neem oil, Fenitrothion50 EC and Emamectin benzoate 5 SG performed best by reducing 59.46, 51.35 & 45.95 % infested pod production respectively. For marketable pod yield, Deltramethrin 2.5 EC, Fenotrothion 50 EC and Curtap 50 SP performed best by producing 5.78, 5.48 & 5.39 ton/hectate at the same time increasing 46.70, 38.58 & 36.80 % marketable pod yield over control respectively. Thus for gross yield, Deltramethrin 2.5 EC, Fenitrothion 50 EC & Curtap 50 SP performed best by producing 6.11, 5.65 & 5.61 ton/ha as well as increasing 41.76, 31.09 & 30.16 % gross pod production. Therefore, Deltramethrin 2.5 EC, Fenitrothion 50 EC & Curtap 50 SP can be recommended for successful country bean cultivation with more production during kharif season.
Pollinators play an important role in production of field bean. Flower visitors, foraging behavior of potential pollinators, role of pollinators in pod set was studied in field bean. Thirty five species of insects belonging to Hymenoptera (89%), Lepidoptera (5%) and Diptera (6%) visited field bean flowers. The major flower visitors included three species of Xylocopa, viz., X. latipes, X. amthystina and an unidentified species of Xylocopa, followed by Ceratina binghami, Trigona sp. and a species of Odynerus. Of these, X. latipes was the most frequent visitor, constituting more than 50 per cent of all visits to flowers. The foraging activity was highest between 10.00h and 14.00h. Xylocopa latipes, forager spent 133±11.7 to 205.6±90.2 secs/trip, visiting 28.6±8.6 to 53.3±31.3 flowers in post monsoon season while, it spent 131±19.6 to 245±131.5 secs/trip in the summer season, visiting 27.3±12.9 to 61.6±42.5 flowers. A forager spent an average 3.9±0.74 sec per flower during post monsoon season and 4.1±.07 in summer season. In pollinator exclusion experiments, plants that were left for open pollination set significantly higher number of pods (66.06 and 61.02% in the first and second seasons respectively) compared to caged plants which were prevented flower visitors (34.48 and 31.80%) (t=22.41 and t= 19.11) indicates the importance of pollinators for crop and value of pollination service amounts to Rs. 53,700/- /ha
Twenty eight Dolichos bean, Lablab purpurea genotypes were screened against pulse beetle, Callosobruchus theobromae and observed for ovipositional preference, number of eggs laid, emergence of adult, per cent adult emergence, number of seeds damaged and per cent seed damage at Bengaluru, Karnataka during 2010-11. GL 77 recorded the lowest seed damage (13.4%) followed by GL 233 (14.69 %) and GL 63 (18.34 %) and these entries were grouped as least susceptible. The highest seed damage was observed in GL 46 (97%) at par with GL 67 (44%), GL 127 (42.75%) and grouped as highly susceptible. None of the entries were completely free from bruchid damage.
An investigation was carried out to assess the variability among 44 germplasm accessions of Dolichos bean (Lablab purpureus L. Sweet) for seven quantitative traits, bruchid and pod borer infestation. The experiment was conducted during kharif season 2013 at University of Agricultural Sciences (UAS), Bangalore, India with two check entries (HA 4 and HA 3) in augmented design in three compact blocks. A substantial variability among the accessions for quantitative traits, bruchid and pod borer infestation except for the number of branches per plant was documented. The estimates of heritability were high for all the traits studied whereas estimates of phenotypic and genotypic coefficients of variation were moderate. The estimates of genotypic and phenotypic coefficients of variation, which reflect average inter-accession differences, are comparatively more useful statistics to understand variability among the germplasm accessions. The germplasm accessions could be grouped into seven clusters following Wards minimum variance clustering approach with significant deviations among clusters. The intra cluster distance was lower compared to inter cluster distance. Some of the germplasm accessions were superior to the check HA-4. These results are discussed in relation to suitable strategies to be adopted for breeding Dolichos bean for improved productivity.
The development of alternative control tactics to insecticides will facilitate a more sustainable holistic approach to Dolichos pod borer management. Present investigations were carried out to identify the sources of resistance to pod borers and its mechanism in Dolichos bean accessions.
The pod borer complex on Dolichos bean consisted of mainly Maruca vitrata, Helicoverpa armigera and Callosobruchus theobromae. Observations recorded for two years revealed the infestation pattern gradually increased from 3rd week of September peaked during 4th week of October and declined from 4th week of November. Two accessions viz., GL 233 and GL 426 proved moderately tolerant to pod borers infestation.
Experiments conducted on antixenosis revealed that GL 233, GL 426, GL 357 and GL 187 recorded minimum number of eggs compared to HA 4 (susceptible check) under no choice, dual choice and multi choice conditions. Experiments conducted on antibiosis revealed that GL 233, GL 426, GL 357 and GL 187 did not favourably support the completion of Helicoverpa life cycle.
The similarity indices using RAPD primers revealed that the cluster I consisted of five accessions (GL 357, GL 63, GL 426, GL 187 and GL 233) showing moderate pod borer infestation (≥27%) and remaining accessions are in the cluster II showing high pod borer infestation (≥50%).
The GC-EAD detection of pod exudates have shown Alpha-pinene, cis-3-Hexenyl acetate, 2 Do-Decenoic acid and E-15-Heptadecenal that elicited positive antennal responses from mated female Helicoverpa moths implicating these volatile components were responsible for attracting and orientating to Dolichos bean pods or plants.
Experiments on oviposition and pod damage by bruchids revealed that preferred stage for oviposition was 70 days after sowing (DAS) to 80 DAS crop with 3.67 eggs per five pods to 4.33 eggs per five pods, respectively and per cent pod damage was up to 87 per cent.