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Open Access
Biology and biometry of Neochetine elchhorniae warner (Curculionidae: Coleoptera) and the nature of damage caused by it on Eichhornia crassipes (mart)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1990) Sreekumar, K M; KAU; Joseph, D
The biology, morphology, biometrics and dispersal pattern of the weevil Neochetina eichhorniae Warner and the nature and extent of damage caused by it on water hyacinth (Eichhornia crassipes (Mart.) were studied. An indirect method of estimating the field population was also attempted. The insect laid the eggs beneath the epidermis of plant parts. Incubation period was 6.6 days and the hatching percentage was 93.2. The larvae fed by tunnelling, and the first, second and third larval instars were completed in 8-10, 13-16 and 13-17 days, respectively. The cocoon was attached to the live roots of the plant and the pupation was just below the water surface. The pupal period was 16.6 days. Adult female longevity was 75.3 days while that of the male was 172.3 days. Pre-oviposit iona I period was 49 days and the total number of eggs produced during the whole life period was 462.5. The head capsule width of first, second and third instar larvae were 0.3, 0.488 and 0.693 mm respectively. In adult males, the average distance between the antennal socket and the tip of the rostrum was 0.259 mm and it was 0.487 mm in females. This character helps in the identification of sexes. No microbes or mites were recorded as natural enemies. The predators were the common non-specific aquatic insects like dytiscid beetle, giant water bug, dragon fly naiads and back swimmers.
Open Access
Biology and Population Build up of the Rice Whitebacked Planthopper, Sogatella furcifera (Horvath) on Different Rice Varieties
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1990) Ajith, P P; KAU; Madhavan Nair, G
Investigations were carried out in the College of Agriculture, Vellayani during 1988 to identify cultivars resistant to the white backed planthopper, S. furcifera from among the high yielding rice varities commonly cultivated in Kerala. The rice cultivars Cul 126, Cul 93, Ptb 33, Karthika, Pavizham, Jyothi, Triveni and TN-1 were chosen for preliminary screening by seed box screening, free-choice and no-choice tests and by tests on orientation and settling response and population build up. In the seed box screening and free choice and no choice tests, the cultivar Cul 126 recorded the lowest damage and the cultivar TN-1 showed the highest damage, indicating resistance in the former and susceptibility in the latter. The cultivar Jyothi did not differ from Cul 126 and the cultivars Cul 93, Ptb 33, Pavizham and Karthika showed intermediate levels of resistance. In the orientation and settling response test the highest number of S. furcifera nymphs were seen settled on TN-1, where as it was the lowest on Cul 126 and it was followed by Jyothi, indicating a clear preference to the susceptible TN-1. The insect multiplied faster and in greater number on TN-1 and the total count was about thirty times more on TN-1 as compared to that on Cul 126 at 60 days after release. Based on the results of the preliminary screening trials, the cultivar Cul 126 and Jyothi (resistant), Pavizham and Karthika (moderately resistant) and TN-1 (susceptible check) were selected for studying the mechanisms of resistance. In the experiment to study the ovipositional preference of the insects it was found that the susceptible TN – 1 and the resistant Cul 126 received the highest and lowest number of eggs respectively. It was also revealed that the leaf sheath received more eggs than the leaf blade. The antibiosis factor in the cultivars was investigated in terms of nymphal duration, nymphal survival, sex ratio of emerging adults, adult longevity, fecundity and hatching percentage of eggs in three growth stages of plants, namely, seedling, tillering and booting stages. The insects from the susceptible TN – 1 had the shortest nymphal duration and the longest adult longevity. The percentage of nymphal survival, fecundity and female/male ratio of the emerging adults were also the highest on TN -1. However, the insects from Cul 126, and Jyothi had longer nymphal duration and shorter adult longevity. The survival, fecundity and female/male ratio of the emerging adults from these cultivars were also lower as compared to TN – 1. The results were uniform in all the three growth stages of the crop. No difference could be observed in the hatching percentage of eggs in the test cultivars in the seedling stage, but in the tillering and booting stages the eggs on TN – 1 showed higher hatching percentage. The results indicated the presence of antibiosis factor in the resistant cultivars, Cul 126 and Jyothi. These results were further confirmed in the experiment on the feeding rate of the insect on the test cultivars. Insects on TN-1 produced the largest area of honey dew spots as compared to others in all the three growth stages showing significantly higher feeding rates. The feeding rate in Cul 126 was the lowest. The effect of crowing of first instar nymphs was more pronounced on the insects on TN-1. The survival percentage was the maximum in crowing at the rate of 25 and it dwindled substantially in the susceptible and resistant cultivars alike in crowding at the rate of 100. Crowding did not have any effect on the sex ratio and brachyptery of emerging adults. When S. furcifera and N. lugens were released together in different proportions, the latter surpassed the former in total number in all the cultivars when counts were taken at 60 days after release of the insects. The result indicated that in cultivars resistant or susceptible to both the insects, N. lugens established a numerical superiority over S. furcifera. In studies to identify the wet land weeds which serve as alternate hosts to S. furcifera, it was found that the insects oviposited in none of the weed plants tested. The nymphs could survive only on Echinochloa colona and Panicum repens.
Open Access
Mass trapping of the sweet potato weevil (Coleoptera: Curculionidae) males using sex pheromone
(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 1993) Mini, E S; KAU; Sitarama Rao, S
The efficacy of the synthetic pheromone of C. formicarius elegantulus in attracting the males of C. formicarius formicarius was tested in the field. The effect of continuous mass trapping of adult males on the population build up of the pest in the field was assessed. The effect of different doses of pheromone as influenced by the trap designs was also assessed. Low cost traps designed and fabricated out of locally available materials were tested in the field and incremental benefit of treatments was worked out. The range of attraction of pheromone doses was assessed by analysing the recapture data of marked males released at different distances from the pheromone baited traps. The results indicated that the weevils were most active during the night as is evidenced by higher capture of weevils at morning observations than those in the evening observations. The weevil catch was not significantly influenced by the higher doses of pheromone. Day light affected the flight pattern of weevils while the moon phases have no significant effect. continued attraction of males towards the pheromone baited traps indicated their effectiveness inspite of the presence of virgin females in the field. The pheromone doses were effective in checking the rapid build up of the pest in the field as evidenced by the non reduction in vine weight. Among the three trap designs polythene bag trap was the cheapest one to install and resulted in the most favourable C : B ratio. The attraction of the pheromone doses decreased with increase in the distance of release from the pheromone source. A distance of 25 m was found to be ideal for placement of traps in the field. The cheapness of traps facilitate installation of large number of traps at reasonable increase in cost.
Open Access
Effect of chitin synthesis inhibitors on rice swarming caterpillar spodoptera mauritia and rice moth corcyra cephalonica and a larval parasitoid bracon brevicornis
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1991) Prathapan, K D; KAU; Dale, D
Effects of four chitin synthesis inhibitors viz. diflubenzuron, chlorfluazuron, PH 70-23 and BASF LAB 153 959 I were assessed on two insect pests, the rice swarming caterpillar Spodoptera mauritia ( Boisduval) and rice moth Corcyra cephalonica (Stainton) and on its larval parasitoid Bracon brevicornis (Wesmael). Ovicidal action was assessed by treating one and two-day old eggs of S. mauritia in aqueous and mathanilic media. It was low in aqueous medium. But in methanolic medium diflubenzuron and the highest doses of the other three compounds showed enhanced action. In general, high ovicidal action was observed in methanolic medium. There was no significant difference between one and two-day old eggs in their susceptibility to chitin synthesis inhibitors. Chlorfluazuron was the most toxic causing cent per cent mortality at doses as low as 2 x 10 -5% when treated on second and fifth instar larvae of S. mauritia. Diflubenzuron, PH 70-23 and BASF LAB 153 959 I were also highly effective. Second instar larvae were more susceptible than fifth instar ones. Besides stomach action, a high degree of contact action was also observed. Final instar larvae of S. mauritia when treated with the test chemicals, produced larval-pupal intermediates and caused pupal mortality and emergence of deformed adults. All the four moult inhibitors were highly active during larval – pupal transformations. Pupae were less susceptible to chitin synthesis inhibitors. Yet, some treatments caused mortality and emergence of deformed adults. Chlorfluazuron was the most toxic to pupae. Fecundity, hatchability of eggs and longevity were reduced when the male moths of S. mauritia were fed on sugar solution containing the moult inhibitors. Antifeedant action of the chitin synthesis inhibitors was found to be less pronounced. Residual effect of all the four compounds persisted on the treated rice foliage throughout a study period of 36 days. But the efficacy of residues exposed to sunlight and rain was very low. Ovicidal action of the moult inhibitors was low to moderate on one and four-day old eggs of C. cephalonica in aqueous medium. In methanolic medium diflubenzuron at 2 x 10 -1 %, 2 x 10 -2 % and 2 x 10 -3 % and PH 70-23 and BASF LAB 153 959 I at 2 x 10 -1 % caused enhanced ovicidal action. In general there was no significant difference between the susceptibility of one and four-day old eggs. Chlorfluazuron was found to be the most toxic compound against larvae of C. cephalonica followed by BASF LAB 153 959 I. Diflubenzuron and PH 70-23 were less effective. Early larval instars were more susceptible. Contact action of compounds other than chlorfluazuron was low. Larval – pupal intermediates, pupal mortality and emergence of deformed adults were resulted when the last instar larvae of C. cephalonica were treated with the chemicals. Chlorfluazuron was found to be the most toxic compound. Prepupal treatment also caused the above juvenomimetic effects. But treatments other than chlorfluazuron 2 x 10 – 2% were less effective. Treatment of pupae of C. cephalonica resulted in pupal mortality and emergence of deformed adults. But pupae were less susceptible to the moult inhibitors as compared to the larval stages. External application of Chitin synthesis inhibitors to moths of C. cephalonica had no adverse had no adverse effect on fecundity, hatchability of eggs and longevity of the treated moths. Chlorfluazuron was found to inhibit the emergence of adult parasites from treated hosts and adversely affect the progeny production of B. brevicornis. Diflubenzuron, PH 70-23 and BASF LAB 153 959 I were non-toxic or only slightly toxic to the parasite.
Open Access
Biology of banana pseudostem weevil Odoiporus longicollis Oliv. (Coleoptera : Curculionidae)
(Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1992) Jayasree, T V; KAU; Jim Thomas
The Banana Pseudostem Weevil, Odoiporus longicollis Oliv., considered as one of the destructive pests in North and North East India is very recently found to be causing wide spread damage in the banana growing tracts of Ernakulam and Trissur districts of Kerala. The present investigation was envisaged to properly understand about the nature of attack, symptomatology, bio-ecology, morphology and the preliminary control measures of the pest species under both field and laboratory conditions. The insect pest is associated with the banana plants throughout the year in Kerala in overlapping generations with its maximum population during both the monsoon periods. This insect has a very congenial condition in Kerala for their survival and multiplication in general and its hot spots of infestation were identified to be around Alwaye-Perumbavoor regions in Ernakulam District. Of late the infestation was observed to be spreading to other Districts also. The banana varieties more susceptible to its attack were found to be Nendran, Palayankodan and Poovan while; Njalipoovan was relatively tolerant. The adult weevils preferred to oviposit on the outersheaths on 3-4 months old plants coinciding with the peduncle formation at a height ranging from 3-4 meter above ground level. The weevil grubs bored into the pseudostem portions and cause extensive tunnelling and riddling leading to weakening of growth, delayed flower emergence, smalling of bunches and finally breakage and lodging leading to partial or complete loss of the crop. The biology, morphology and biomorphometrics of the insect under laboratory conditions were worked out in detail. Because of the peculiar nature of the plant and the fruit produce, as well as the type and nature of the pest species, chemical means of control by spray impregnation of natural products, injection of systemic insecticide through root, rhizome and pseudostem portions and padding technique with fumigant insecticide gave inconclusive results. Bio-control with the parasitic nematode, DD-136, Steinernema sp. eventhough showed good in vitro mortality under lab conditions, it was not successful under field condition. From the above studies, it was found that, to contain the pseudostem weevil infestation effectively, an integrated pest management strategy with special emphasis on cultural techniques on a community basis should be evolved and practiced.
Open Access
Host resistance in cowpea ( Vigna unguiculata (L .) Walp) to the pod borer Maruca testulalis (Geyer) (PyralidaeiLepidoptera)
(Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1992) Anitha Kumari, V; KAU; Sheila, M K
An investigation on the host resistance in cowpea ( Vigna unguiculata (L.) Walp) to the pod borer Maruca testulalis (Geyer) was carried out by screening 100 varieties of cowpea during 1990 - 91. These were classified into highly susceptible, moderately susceptible and moderately resistant classes. This study rules out the chance of any of the varieties screened to be resistant to this particular pest. Selected accessions from the three different classes based on the field evaluation, were subjected to artificial infestation by the first instar larvae of M. testulalis on caged plants in the green house. Here too, the susceptibility spectrum was found to be similar to the trend observed in the field trial. The accession V30 was identified to be the most moderately resistant type and V100 as the most susceptible one. In the studies on antibiosis it was found that the larvae reared on moderately resistant type took longer durations of development as compared to the susceptible ones. The larval survival as well- as the adult emergence was lower in the resistant types The highly susceptible accessions produced more females than the resistant lines. The fecundity of F females was adversely affected when the larvae were reared on the moderately resistant accessions. Among the biophysical components, though the pod wall thickness and pubescence of the pods did not show any correlation with the level of borer infestation, the length of flower stalks, disposition of corolla, calyx and seeds and the nature of seed testa, had a positive influence on its distribution. Positive correlations were also detected between the mean percentage of total sugars, crude protein, amino acids and nitrogen in the pods on the one hand and pod damage on the other.
Open Access
Management of pests of amaranthus and bhindi using plant extracts
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1990) Srinath, B; KAU; Sasidharan Pillai, K
Water extracts of eight locally available plants of known insect control potential were screened at 2 and 4 per cent concentrations against pests of amaranthus and bhindi in a pot culture experiment in comparison with carbaryl and tobacco decoction. T. nerifolia followed by A. indica, C. infortunatum and E. odoratum were highly effective against P. basalis on amaranthus and A. gossypii on bhindi. C. infortunatum and T. nerifolia followed by A. indica, N. oleander and E. odoratum were effective against A. biquttula biguttula. T. nerifolia and A. indica followed C. infortunatum and E. odoratum reduced damage caused by E. vittella. Carbaryl 0.2 per cent was superior to plant extracts and tobacco decotion was effective only against aphids. A laboratory study was undertaken for augmenting the toxicity of five aqueous plant extracts by adding with teepol, soap and coconut oil at varying concentrations and combinations. Toxicity of eight and four per cent extracts of C. infortunatum and eight per cent extract of T. nerifolia with teepol, coconut oil and soap reduced the adult emergence of S. litura. A. indica and T. nerifolia were more effective against A. gossypii when the extracts were mixed with soapwater. Teepol and coconut oil also had the same effect with eight per cent T. nerifolia. Field experiment was conducted with the extracts of A. indica, T. nerifolia and C. infortunatum at two and four per cent concentrations without and with soap against pests of amaranthus and bhindi using carbaryl and tobacco decoction as standards. Carbaryl was superior to plant extracts in controlling the population of pests. Four per cent extracts of A. indica, two and four per cent extracts of T. nerifolia and C. infortunatum protected amaranthus against A. crenulata and P. basalis. Toxicity of the extracts A. indica and T. nerifolia was augmented with soap at lower concentration. All the plant extracts increased the crop yield but lesser then carbaryl. Tobaco decoctin failed to control the pests incidence and to increase the yield. Two and four per cent extracts of T. nerifolia caused heavy mortality of A. gossypii. Four per cent extract of A. indica was more effective than carbaryl followed by C. infortunatum, and T. nerifolia against A. crenulata on bhindi. C. infortunatum with soap was efficient against A. biguttula biguttula. Four per cent extracts of T. nerifolia and A. indica were highly effective against E. vitella. T. nerifolia four per cent was effective against S. derogate. Plant extracts were not toxic as carbaryl to C. sexmaculata. All the plant extracts other than at 2 per cent concentration increased the yield and T. nerifolia recorded maximum, but lesser than carbaryl. Tobacco decoctin had no impact on yield. Toxicity of 2 per cent extract of T. nerifolia was augmented with soap against pests of bhindi.
Open Access
Impact of insecticides on the flora and fauna in the soil ecosystem of banana plantation
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1993) Alice Renta Packia Sujeeth, J; KAU; Mammen, K V
Possible adverse effects of the insectisides recommended for the control of pests/diseases of banana in Kerala, on the useful soil organisms and the consequent impact on the banana ecosystem were studied in detail through a field experiment and follow up laboratory investigations. The results revealed: (1) Earthworm population was adversely affected with HCH even in low doses upto two months after the treatment. With carbofuran soon after the first and second application the population declined but restored with in two months. In the case of phorate the first treatment alone caused significant adverse effect while the second and third did not cause any significant effect on the earthworms. Even in carbofuran and phorate treatments earthworms. Even in carbofuran and phorate treatments earthworm population came on par with control two months before the harvest. (2) Parasitic nematodes were unaffected by HCH treatment. With carbofuran significant reduction in the population of parasitic nematode was noted after two applications of the insecticide. The nematicidal effect was seen lost throughout the period of observations from the eighth month. In phorate treatment significant reduction was observed only after three consecutive applications of the toxicant. The overall reduction caused by phorate was not adequate. Carbofuran was hence better to control parasitic nematodes than phorate. In both the cause the low level of nematode population in soil may be attributed to the lack of response to the nematicides recommended for the control of the pest. (3) HCH treatment was not at all toxic to non-parasitic nematodes. In the case of carbofuran and phorate low population was observed throughout, while significant reduction was observed for a short while after the first application of the insecticides only. (4) Collembolan and mite population was not reduced by HCH treatment. Significant reduction was observed for two months after the first and second applications of carbofuran and phorate. Adverse effect was then lost and the population was maintained on par with control till harvest. (5) The bacterial count was low throughout in HCH treatment. Though the carbofuran reduced the bacterial population it was revived in two months time. Phorate suppressed the bacterial population after first two applications, while with the third application slight enhancement was observed on the population and it was restored on par with control before harvest of the crop. (6) In fourth and eighth month a suppressing effect of HCH on actimycetes was noted and a stimulatory effect was observed during the sixth month. In carbofuran no significant reduction was observed upto three months and later on no reduction was noted. In phorate significant reduction was observed after the first and second application and the actinomycets population was then restored and remained unaffected till harvest. (7) Significant reduction of fungi was observed during the third and fourth months after planting in HCH treatment. In carbofuran slight reduction was noted after first and second application. The population was then restored. In phorate slight reduction was noted after two applications and it was restored in the next month itself. The third application showed stimulatory effect and the population was higher than that observed in control in subsequent observations. (8) The organic matter content in treatments and control remained on par and hence the humification process in banana ecosystem, through the activity of the soil organisms, was not seen affected by the application of insecticides. The variations in pH and moisture content of a soil in control plots and treatments also were not statistically significant. (9) Changes in the correlation of soil parameters with the beneficial organisms in control and treatments also did not show any definite trend. This may be due to low variability in the data on the population levels as well as the soil parameters. In general the treatments did not alter the population of the soil fauna and flora in the ecosystem to cause any adverse persistent effect.
Open Access
Studies on the entomogenous fungus associated with cowpea aphid
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1992) Faizal, MH; KAU; Susamma Mathai
Studies were conducted on the entomogenous fungus Fusarium pallidoroseum (Cooks) Sacc. infecting cowpea aphid Aphis craccivora Koch. The infected aphids turned pale and assumed brownish black discolouration. Death occurred in 24 to 72 hours after infection and mycelial growth appeared on the cadavers 24 to 48 hours after death. For mass production of the fungus, wheat bran and rice bran appeared to be comparatively suitable as they recorded maximum growth, sporulation and virulence of the pathogen. Maximum sporulation was noticed 8 days after inoculation. Culture substrates subjected to full heat sterilization produced maximum growth and sporulation of the fungus followed by those subjected to full solarization. A mortality per cent of 99.57 was observed when aphids were sprayed with culture filtrate of F. pallidoroseum grown in Richard’s medium indicating the presence of toxins. Studies on the effect of pesticides on the growth of the fungus showed that mercaptothion and monocrotophos were the least inhibitory. Fenthion showed the least inhibition of sporulation. HCH, captan and zineb completely inhibited the growth. Sporulation was completely inhibited in all the fungicidal treatments. Under laboratory conditions spore suspension of the fungus in water was found to be superior to the spore formulations tried. Among the formulations wettable powder with diatomaceous earth as inert material was found to cause more mortality followed by wettable powder with talc as inert material. Dust using talc as inert material was found to be the least effective. Spore suspension in water, wettable powder formulation of fungal spores with diatomaceoue earth as inert material and quinalphos 0.05 per cent were found to be equally effective in bringing down the population of aphids under field conditions. The virulence of spores of F. pallidoroseum in formulation was found to decrease with increase in storage period and it retained substantial virulence up to four days of storage.

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