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:
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.
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.
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.
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.
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.
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.
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.
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).
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 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 borer’s viz., L. boeticus (15 larvae per quadrate), E. atomosa (17.75 larvae per quadrate),
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).