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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
Control of aphis craccivora koch. with fungal pathogens and their impact on the natural enemies of the pest
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1989) Hareendranath, V; KAU; Vasudevan Nair, K P
Studies were made to collect information on the population fluctuation of pea aphid Aphis craccivora Koch. a regular pest of cowpea in relation to time of planting and stage of the crop. The population fluctuation of pea aphid in relation to the prevailing weather factors and the predators were also investigated to collect information on host predator interactions and interrelations. A survey on the occurrence of fungal pathogens associated with pea aphid was conducted in the pulse crops raised at the Instructional Farm, College of Agriculture, Vellayani and adjacent farmers fields. The suspected fungi were isolated and their pathogencity tested in the laboratory. Pathogencity could be proved only in the case of Fusarium pallidoroseum (Cooke) Sacc. Detailed studies were made on its growth, sporulation and pathogenicity using different artificial culture media. It was observed that the cowpea crop planted during November recorded maximum population of pea aphid followed by crop planted during October and December. Lowest population of pea aphid was noticed in the crop planted during March. The active reproductive stage of the crop recorded maximum population of pea aphids. Correlation studies with weather factors and predator population revealed that relative humidity and predator population was positively correlated with the population of pea aphid. Regression analysis of the data obtained indicated that 84 per cent of variation of population could be accounted by the variables under study. Partial regression coefficient of the aphid population and relative humidity was found to be positive and significant. Partial regression coefficient between pea aphid population and predator population was also positive and highly significant. Studies on the pathogenicity of F. pallidoroseum showed that pea aphid infected with the fungus turned pale and assumed a brownish black discolouration. Death occurred in 48 to 72 hours after infection and white mycelial growth appeared on the cadavers 24 to 48 hours after death. Growth, sporulation and virulence of the fungus was found to be superior in Sabouraud medium followed by potato dextrose agar. Sporulation was maximum in 6 day old culture and virulence was highest in 6 day and 7 day old cultures. For mass production of the fungus broken maize grain appeared to be the most suitable media followed by tapioca chips and jack seed as they produced maximum number of spores. Studies on the safety aspects of the pathogen showed that the fungus was not pathogenic to the crop plants tested viz. rice, bhindi, chillies and tomato and also to the predator Menochilus sexmaculata. Bioassay showed that LC50 of the fungus to pea aphid was 3.408 x 10 6 spores per ml. Field experiment to test the efficacy of the fungus in controlling aphid population revealed that the fungus at the rate of 7 to 10 6 spores per ml and 3.5 x 10 6 spores per ml was as effective as the insecticide quinalphos 0.05 per cent. The fungal treatment did not show any harmful effects on predator population in the field.
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
Evaluation of multi x bi bivoltine hybrids of silkworm
(1998) Rajeni, Narayanan; KAU; Ranjith, A M
In a study undertaken to evaluate the region and season specific multi x bi and bivoltine hybrids of silkworm Bombyx mori, for commercial exploitation in Kerala, six hybrids of silkworm were reared using K-2 and S-36 mulberry varieties under Vellanikkara condition. The crosses used were PM x NB18, PM X NB4D2 and their reciprocals, NB4D2 x NB18 and its reciprocal and PM as check. The evaluation was carried out based on characters like leaf consumption, larval duration and weight, cocoon and shell weights, shell ratio percentage, average filament length, denier, reelability and renditta. The climatic factors were also correlated with major economic characters of silkworm. The present study confirms the superiority of bivoItine silkworm hybrids like NB4D2 x NBI8 and NB18 x NB4D2 justifying their wide acceptance in states other than Kerala. It is evident that if rearing is done in a systematic way, by strictly adhering to the brushing period in correlation with the seasons and if the use of high quality mulberry varieties is advocated these crosses will yield good returns in Veil ani kkara. Though the various economic parameters reflected a variable trend, ultimately when the average filament length/g cocoon, shell ratio percentage and cocoon weight were considered, the bivoltine hybrids performed superior to the others.
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
Relative susceptibility of cashew types to infestation by the tea mosquito helopoltis antonii signoret (hemiptera:miridae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1981) Thomas, K M; KAU; Abraham, C C
The relative susceptibility of fourteen cashew accessions (Anacardium occidentale L.) to infestation by the tea mosquito bug Helopeltis antonii signoret (miridae: HEmiptera ) was evaluated in the field experiments conducted at the Cashew Research Station , Madakathara during September 1979-March1980. The field damage Intensites and the extent of damage Inflicted by the insect consequent on confinement on shoots and panicles were recored on a 0-5 scale and it was found that the accessions 22,1112, 1430 and 1097 were least susceptible with regard to the intensity of natural field infestation of the vegetative shoots. Regarding the intensity of field infestation on floral branches, the accessions, 22, 1112,1352,1469 and 1097 were significantly less susceptible than the other types . With reference to the intensity of damage to vegetative shoots under confinement none of the accessions was found to be promising . The accession numbers 1219 , 1469 and 1431 were found to be least susceptible to H. antonii infestation under confinement on floral branches . Since the damage to the floral branches, particularly under confinement , Is relatively more important factor responsible for yield reduction these trees can be identified to be relatively more promising . The influence of certain biochemical factors (total nitrogen , soluable sugar and tannins ) on pest infestation in shoots and floral branches was ascertained by working out simple correlation coefficients. The only significant association detected was between the tannin content in the vegetative shoots on the one hand and the pest infestation intensities under confinement , on the other. The shade intensities within the canopies had no the extent of susceptibility to the pest. The tree architecture patterns were found to be of two basic types, namely, extensively branching (spreading ) and intensively branching (bushy ). Variations in the canopy configuration did not influence the susceptibility trends. The inconsistencies in the relative susceptibility of different accession with reference to shoot and panicle damage intensities have been discussed.
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
Bioecology of orthogalumna terebrants wallwork on waterhyacinth
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1994) Babykala, P; KAU; Joy, P J
The mite biology, morphology, nature of extent of damage and interaction with N. eichhorniae were studied. The might laid solitary eggs sideways to the oviposition holes, deeply embedded in the aerenchyma cells. The incubation period was 5.8 days. The larvae and nymphs fed by making galleries. The larvae, proto and deuto nymphal stages were completed in 3 days each, while that of tritonymph took 4 days. The duration of inactive stages from larva to proto, proto to deuto and deuto to tritonymphal stage were 1.6 days each, whereas from tritonymph to adult, it was 3 days. Adult longevity was 57.3 days. pre-ovipositional period was 4 days and the total number of eggs produced during the whole life period was 41.5 eggs. The larvae have three pairs of legs but no genital opening. The nymphal stages have four pairs of legs, ending in single claws. The proto, deuto and tritonymphal stages, have one, two and three pairs of genital papillae respectively. This character helps in identification of larval and nymphal stages. The adults are pteromorphs and sexual dimorphism is absent. Sensillus is relatively short with curved stem and globular roughened head. Terminally the tarsus of the leg has three claws on a short peduncle the lateral claws more slender than the median and sharply angled. The larval and nymphal feeding produces galleries on leaves of waterrhyacinth resulting in brown streaks on the leaf lamina. Such brown streaks later coalesce to form large brown areas, leading to drying up of the entire leaf. As the mite load increased from ten to eighty the number of plants and number of leaves showed significant reduction 90 days after release. The extent of damage caused by O. terebrantis with or without weevil under open and partially shaded conditions of waterhyacinth plants was experimented upon, and it showed that, the root length, petiole length ( in open condition), laminar width and length, number of leaves and number of plants under both light intensities (partially shaded and open condition), in general showed a decreasing trend. The plants in tanks having ten weevils alone per tank and 10 weevils plus 100 mites per tank under partially shaded conditions collapsed within 60 days, whereas in open condition of that having 10 weevils plus 100 mites per tank, all the plants collapsed by the 75th day. In the treatment with ten weevils alone per tank in open condition the collapse occurred only at 105 days. In the treatment with 100 mites alone per tank, there was no collapse of plants upto 105 days (in both conditions). The number of mite galleries and mite population per leaf with Neochetina feeding marks was comparatively more in the presence of weevils than in their absence. Fungi like Fusarium, Aspergillus and Rhizopus were isolated and also the spider mite and insects like aphids and grasshoppers were noticed.
Open Access
Plant parasitic nematodes associated with pineapple in Kerala
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1981) Hamza Koya, C P; KAU; Venkitesan, T S
As a part of the studies on the occurrence of plant parasitic nematodes associated with pineapple in Kerala, a survey was carried out in different agro climatic regions of the Kerala State and it was found that R. reniformis occurred in more than 76 per cent of the locations sampled. Helicotylenchus spp. were recorded in about 50 per cent of the locations. The other plant parasitic nematodes detected in association with the crop included Meloidogyne spp., Creconemoides spp., Pratylenchus spp., Hoplolaimus and Hemicyclophora occurred in very low population densities. A new species of Helicotylenchus closely resembling H. digitatus ( Hussain and Siddique, 1964) but differing with respect to spear knob characters and location of excretory pore has been reported to be associated with the crop. The pot culture trial with M. incognita indicated that this nematode could not induce pathogenic effect on the cv kew even at the highest inoculum levels of 10,000 larvae per 7.5 kg soil during the period of 180 days.

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