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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
Isolation of the bioactive pinciples of thevetia nerlifolia juss.(Apocynaceae) and determination of their biological activities
(Department of Entomology, College of Agriculture, Vellayani, 1996) Hebsi, Bai; KAU; George, Koshy
Fresh and dried leaves and seeds of Thevetia neriifolia were evaluated for their antifeedant activity against Henosepilachna vigintioctopunctata, using acetone, benzene, ethanol, hexane, methanol and water as extractants. Based on the percentage of leaf protection, seed extracts were superior to the leaf extracts. Fresh leaf and dried leaf extracts were on par. Among the solvents, ethanol and methanol gave maximum leaf protection closely followed by water. Based on larval starvation, seed extracts were superior to leaf extracts and fresh leaf extracts were significantly better than dried leaf extracts. Water, methanol and ethanol were on par for extracting plant tissues. Soaking of powered plant material well in solvents for 48 hours and filteration was found as effective as soxhlet method for extracting antifeedant components from leaves and seeds of T. neriifolia. Leaves and seeds of the plant showed conspicuous hormonal/sterilant activity on Dysdercus cingulatus and the response was dose dependent. This was evident in post treatment larval mortality, prolonged preovipositional period, emergence of malformed adults and reduced fecundity. Adult longevity, incubation period and hatching percentage of eggs were not affected. Forty per cent and ten per cent of leaf and seed extracts as well as 20 and 5 per cent extracts of the same came on par in juvenomimetic effect. The results showed that seeds were four times more effective than the leaves in their juvenomimetic effect on D. cingulatus. The length of ovary, number of oocytes per ovariole and size of basal, penultimate and antepenultimate oocytes were significantly lower in seed and leaf extract treated females of D. cingulatus. Closer examination of the data revealed that growth of ovary was delayed rather than suppressed by the plant extracts. Levels of protein, glycogen and lipid contents observed on ovary, fat body and haemolymph of treated and untreated insects from first to fifth day after emergence indicated a delay in vitellogenesis and oocyte development in treated insects. Consequently previposition period was prolonged. The effect observed is similar to the effect of chemosterilants reported on some insects earlier. Results indicated that reduction in fecundity of D. cingulatus may be due to the chemosterilant action of T. neriifolia extracts. Bioassay studies in the laboratory revealed the low contact toxicity of leaf and seed extracts of T. neriifolia to S. litura and H. vigintioctopunctata. Chromatographic isolation of different fractions of ethanol extracts of fresh leaf and seed yielded six bioactive fractions from the leaf and four from the seed. Fractions III and IV were absent in seeds. Fractions IV, V and VI obtained from leaves and V and VI from seeds had far higher activity than the remaining fractions and they were on par in their antifeedant effect and larval starvation on H. vigintioctopunctata. Available active fractions were more concentrated in seeds than in leaves. Laboratory studies showed the safety of leaf and seed extracts of T. neriifolia at field doses to Chrysocharis johnsoni, the most important parasite of H. vigintioctopunctata in Kerala. Toxicological studies in albino mice and rats revealed that 400 mg/kg body weight was the LD50 dose of seed extract of T.neriifolia while doses upto 1000mg/kg body weight of leaf extract was not toxic to the animals. Haematological picture of animals chronically exposed to the extracts showed marginal deviations in the haemoglobin content, RBC count, serum cholesterol, SGOT levels in seed extract treated animals from the permissible safe range. Leaf extract treatment caused deviations in SGOT and serum cholesterol. Vacuolation, cytoplasmic acidophilia and degenerative changes in the liver and heart tissues and inflammation of kidney were observed in animals treated with seed extract. Adverse effects of leaf extract were negligible. Replicated field experiments were conducted for two seasons on bittergourd and amaranthus to evaluate the efficacy of crude extracts of T. neriifolia in controlling their major pests. All the extracts viz., ethanol and water extracts of dried and fresh leaves and seed reduced the pest population and the extent of leaf damage. Seed extract was on par with the insecticide check, carbary 1 (0.15 per cent) in bittergourd and malathion (0.1 per cent) in amaranthus. Fresh leaf extract was on par with the seed extract and was superior to extracts of dried leaf in reducing pest population and increasing yield of both the crops. Water extracts of leaves and seed were found equally good for checking the pest population and increasing yield. On cost benefit basis water extracts were found more advantageous to the farmer. Parasitization of egg masses, grubs and pupae in treated plots were on par with control while they were totally missing in the insecticide treated plots. Extracts of T.neriifolia were thus found to be safe to the non – target organisms too. An overall assessment of the results obtained revealed that water extracts of fresh leaf and seed in appropriate doses can be effectively and safely used for the control of important pests of bittergourd and amaranthus without any health hazards and adverse effect on the non target organisms in the agroecosystem. T. neriifolia can be considered as a plant suited for developing effective plant protection chemicals for replacing undersirable synthetic insecticides, especially in integrated pest control calendar.
Open Access
Phytochemicals and vam for management of nematodes in brinjal
(Department of Entomology, College of Agriculture, Vellayani, 1997) Asha, John; KAU; Hebsy, Bai
Aqueous neem leaf extract, neem oil and marotti oil at different concentrations were tested as bare root-dip treatments for their efficacy in containing root-knot nematode infestation in brinjal. Root-dip in neem leaf extract for one hour resulted in significantly better height and number of leaves in the treated plants than nee m oil and marotti oil. Among the different concentrations of neem leaf extract tested, 6.25 and 25 per cent extracts proved more effective. Significant reduction in gall index was also seen in neem leaf extract treated plants. Higher concentrations of the extract (50 and 25 per cent) significantly reduced the number of egg masses produced. But none of the phytochemicals had any adverse effect on the hatching of the egg masses. All the three phytochemicals irrespective of the doses reduced population of the nematode in the soil. An overall assessment of the result established the superiority of neem leaf extract (25 per cent) among the different phytochemicals tested in checking nematode infestation. Different isolates of V AM fungi like, G. fasciculatum, G. etunicatum, G. mosseae, G. constrictum G. monosporum and A. morroweae did not show any significant difference in the growth parameters of brinjal plants (height and number of leaves) at transplanting and one month after transplanting irrespective of the pot size. Later (45 and 60 days after transplanting) significant increase in height and number of leaves were observed in plants raised in soil inoculated with G.etunicatum and G. fasciculatum. Higher percentage of V A mycorrhizal colonisation was observed in plants artificially inoculated with V AM. Plants raised in G. etunicatum G. fasciculatum and G. monosporum recorded significantly lower root-knot indices. The fecundity of the nematode and the number of larvae hatching per eggmass was also significantly reduced in mycorrhizae treated plants. Irrespective of the pot size, G.fasciculatum registered the lowest population per gram root while G. fasciculatum and G. constrictum significantly lowered the nematode population in the soil. Overall assessment of the results revealed G. fasciculatum as the most effective mycorrhizae among the isolates tested for protecting brinjal plants from root-knot infestation. Field trial with bare-root dip in 25 per cent neem leaf extract and insecticides monocrotophos (500 and 250 ppm) and carbosulfan (500 and 250 ppm) nursery treatment with G. fasciculatum and root-dip of the mycorrhizal seedlings in neem leaf extract and nematicides did not show any significant effect on growth parameters of the plant like height, number of leaves and root weight But the . bare-root dip treatment in neem leaf extract and mycorrhizal nursery treatment and bare-root dip treatment in monocrotophos 500 ppm resulted in significant increase in shoot weight. Root-dip in nematicides was definitely superior to root- dip in neem leaf extract and nursery treatment with G. fasciculatum in increasing yield significantly. Bare-root dip in neem leaf extract, nursery treatment with G.fasciculatum also registered significantly higher yield. Root-dip of mycorrhizal seedlings in monocrotophos and carbosulfan were far more superior than the individual treatments in increasing the yield of brinjal. During the early stage (45 DAT) no significant difference was seen in the gall index, number of egg mass per plant and mycorrhizal colonization percentage. Later, as the plant matured a significant difference was seen in these parameters. Root -dip in neither nematicide nor neem leaf extract showed any deleterious effect on mycorrhizal colonisation.
Open Access
Monitoring and management of the pest complex of bitter gourd (Momordica Charantia L.)
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1999) Nandakumar, C; KAU; Saradamma, K
Surveys were conducted in 1995-96 among one hundred bitter gourd farmers in Thiruvananthapuram district. Information on the personal and socio- economic characteristics of the farmers was gathered. Field visits indicated that among the pests at flowering, the jassid, H.phycitis and leaf feeder, D. indica were important. At early harvest, the jassid and fruitfly B. cucurbitae were the major pests. Among the natural enemies observed, the potential ones were Cjohnsoni (parasite on Hseptima), I.scutellare, Msexmaculatus and Snubilis . (predators on A.gossypii). Mosaic was severe in 12 per cent of the plots. Sixty two per cent of the farmers used a combination of mechanical, cultural and chemical measures against pests. Most common pesticides used belonged to the organophosphate group. Farmers in general adopted injudicious methods of chemical control. Seventy per cent farmers relied on mass media and interpersonal cosmopolites for information on plant protection. The most important constraint perceived by farmers was the high cost of inputs viz., plant protection chemicals, manures and fertilizers. Monitoring of fruit fly incidence using Biosense stikatrap (lure) indicated the maximum catch at eleven weeks after sowing. Ten carbofuran smeared banana fruit traps (in yellow coloured coconut shell) were found to be more efficient than one Biosense trap in trapping the fruit fly. 2 Studies on seasonal incidence of the pests and their natural enemies from 1995 to 1996 indicated that they were more from November '95 to April '96. In studies on the assessment of potential natural enemies of pests, the biology and efficacy of Cjohnsoni against epilachna beetle was observed. Among the predators viz., Iscutellare, Msexmaculatus and S.nubilis whose biology and feeding potential was studied, Msexmaculatus was observed as the most efficient predator of aphids. In another set of experiments, the effects of botanicals and chemical pesticides on pests and their natural enemies were studied. The antifeedant effect of botanicals on third instar Hseptima grubs indicated that neem seed oil (three per cent) and nimbecidine (0.40 per cent) were effective. Estimation of the comparative effect of chemical pesticides against the fourth instar Hseptima grubs showed that carbaryl and dimethoate were more effective than quinalphos and malathion. Toxicity studies of botanicals and chemical pesticides to Msexmaculatus grubs and Cjohnsoni adults as well as parasite emergence from treated larval! pupal Hseptima hosts indicated that botanicals were safe whereas, the chemicals were toxic to the natural enemies. Based on the above experiments, the botanicals viz., neem seed oil three per cent, nimbecidine 0.40 per cent and the chemical pesticides,carbaryl 0.15 per cent and dimethoate 0.05 per cent were selected for the pest management trial in bitter gourd. The reaction of five bitter gourd varieties viz., Priya, Arka Harit, Preethi, Priyanka and local to pests was tested in a field trial. Based on pest infestation and yield, Preethi was selected for the pest management trial. 3 The pest management trial was conducted for two seasons (January to April, 1996 and 1997). The results indicated that combination of botanical with chemical pesticide was the best in pest control. Based on the results the following recommendations were suggested as part of IPM strategies in bitter gourd. 1. Use variety 'Preethi' (MC-84) for planting 2. Basal drenching of combination of nee m seed oil three per cent soap emulsion with either dimethoate (0.025 per cent) or carbaryl (0.075 per cent) prior to seeding. This is recommended in areas where pests like pumpkin beetles are endemic. 3. Need based application of above till fruit set to control pests. 4. Apply fungicide (Mancozeb) to control foliar disease (downy mildew). 5. Monitor fruit fly incidence using lure trap. Set yellow painted coconut shell trap's containing carbofuran smeared banana (palayankodan) alternated with carbofuran poisoned ocimum I jaggery (2m spacing) at flowering till final harvest. 6. After fruit set, use (need based) a combination of neem seed oil three per cent soap emulsion and dimethoate 0.025 per cent.
Open Access
Insect pest natural enemy- host plant interaction studies with special reference to the brown planthoper nilaparvata lugens(Stal.)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1999) Haseena, Bhaskar; KAU; Joy, P J
Field surveys were conducted in Kole land and Kuttanad to assess the population of rice BPH, Nilaparvata lugens (Stal) and its natural enemies. Field investigations on the population dynamics of BPH and its natural enemies were carried out on susceptible (Jaya), moderately resistant (Jyothi) and resistant (Kanakom) rice varieties at the rice fields of Rice Research Station, Moncompu during 1997-98. The influence of these varieties on the biology of the pest, the biocontrol efficiency of the major natural enemies and the biology of the mirid predator Cyrtorhinus lividipennis Reuter was studied in the laboratory. Histological and chemical investigations were undertaken to evaluate the factors that contribute to the resistance/susceptibility in them. Results of field survey in Kole land revealed that the population of BPH was far below the economic threshold level (ETL). In Kuttanad, in kayal area during Rabi season and in karappadam tract during Kharif season outbreaks of BPH occurred in some localities due to the indiscriminate use of insecticides resulting in the mortality of natural enemies. The results of the study on population dynamics revealed that the BPH population was significantly high on the susceptible J aya and low on the resistant Kanakom with the population reaching a peak from February to March. The predatory complex of the BPH comprised of the rnirid Cyrtorhinus lividipennis, Lycosa pseudoannulata, Tetragnatha maxillosa, Atypena formosana, Microvelia douglasi atrolineata, Pseudogonatopus sp. and Ophionea nigrofasciata. C. lividipennis was the most predominant predator regulating the hopper population and there exists a density dependent host-predator relationship. The population of the mirid predator on Jaya and Kanakom did not differ significantly. The prey-predator ratio was lowest on the resistant variety and highest on the susceptible variety. Of the weather parameters studied, the minimum -. temperature showed a highly significant negative correlation with the population of N. lugens in all the varieties. BPH reared on the resistant variety recorded longer nymphal duration, decreased nymphal survival and shorter adult longevity indicating the prevalence of antibiosis in the variety. Lesser number of eggs laid, longer pre-oviposition period and shorter oviposition period recorded on Kanakom indicate the antixenosis factor in it. Macrpterous forms of BPH did not develop on the variety . The predator C. lividipennis and Micraspis sp. fed more BPH when reared on the resistant variety. The veliid bug M. d. atrolineata, the spider L. pseudoannulata and the dryinid Pseudogonatopus sp. predated significantly more BPH nymphs on resistant variety at a higher prey density only. However, the dryinid parasitoid consumed significantly fewer number of hoppers on Kanakom at the higher host density. C. lividipennis recorded longer nymphal duration, shorter adult longevity and low fecundity when fed on BPH reared on Kanakom which can be attributed to the low fecundity of N. lugens on Kanakom leading to less availability of food to the mirid. Nymphal duration and adult longevity of C. lividipennis did not vary between the varieties Jaya and Jyothi. Well developed bundle sheath with more frequently distributed schlerenchyma tissue in the culm of the resistant variety seemed to impart resistance in Kanakom along with thicker cuticle. Higher amounts of silica, Zn and Mn and lower amounts of N, K, Ca and Mg were recorded in the culm of the resistant variety compared to moderately resistant and susceptible varieties. The findings strongly suggest the mechanism of antibiosis and antixenosis in the resistant variety Kanakom.
Open Access
Resistance mechanisms against the pseudostem weevil odoiporus longicollis olivier (coleoptera : curculionidae) in banana
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1999) Lalitha, N; KAU; Ranjith, A M
The present investigation on resistance mechanisms against pseudostem weevil Odoiporus longicollis Olivier (Coleoptera:Curculionidae) in banana was undertaken in the Department of Entomology, College of Horticulture, Vellanikkara during 1997-99. In insect-plant interactions, it is always the survival of the fittest. There is also a constant enhancement in the physiological preparedness both by the insect and the host plant to gain the upper hand. It is felt that even though the insect conqu6¥$ the resistance of the host plant in majority of cases, there may be a threshold of insect attack, which would induce plant defenses to deter the attack. It was also possible that some of these plant defenses may be triggered off by enzymes produced in the plant system consequent to the attack. These incitory enzymes or chemicals may be transferred to the offspring, which would make them resistant to attack, by the weevil. Hence, major objectives of the study were to evaluate sucker and in vitro regenerated progenies of infested Nendran (AA B) for resistance against 0. longicollis, to evolve methods for screening resistance under artificial conditions, laboratory rearing of 0. longicollis and identification of morphological, biochemical and anatomical bases of resistance using Nendran as susceptible and Njalipoovan as the resistant source. Preliminary field screening of Musa (AAB) Nendran for resistance against pseudostem weevil was done based on the number of ovipunctures/feeding holes on the pseudostem, surface area of infestation and the size of feeding holes. All of these contributed to the intensity of the attack. The multiplication product of these factors led to the development of a new 0-4 rating scale, for scoring the damage by 0. longicollis in the field. No-choice tests conducted on sucker and in vitro regenerated progenies of such graded mother plants revealed a better performance by plants having lower history of infestation. This suggested the existence of induced resistance involving triggering off of enzymatic reactions. Besides these lower grades, the plantlets of G4 exhibited better tolerance than control by exerting greater potential to stand amidst heavy winds till complete maturity of the bunch. The in vitro regenerated plants performed much better than the sucker derived treatment plants. This offers potential for mass multiplication of such in borne resistance for commercial release. The results obtained so far opens up the possibility of induced resistance that may be genetically inherited to the plantlets from its mother as an evolutionary character. Such triggering mechanism operating in vivo offers greater potential to select resistant clones. The methodology for screening banana for resistance to 0. longicollis by artificial infestation in field situations was standardized. Four adult weevils in the sex ratio 1: 1 (2!f' and 2 r:J) was found to be optimum to create moderate levels of infestation during the most favourable season (May-August). Mass rearing of 0. longicollis in laboratory conditions using natural diet was quite successful for maintaining a large-scale population throughout the year. A continuous supply of uniformly aged test insects for exposing the experimental plants at specific pest load was made possible by this. Studies involving the duration of development of the weevil revealed acute antibiosis in Njalipoovan manifested by reduced egg laying prolonged duration of life cycle, reduced hatching of eggs (39.5%) and reduced adult emergence from eggs (29.7%) in contrast to 94.9 per cent hatching of eggs and 9l.3 per cent adult emergence in Nendran. A no-choice test was designed to study the appropriate age of Nendran from which it becomes susceptible to infestation. Results indicated a distinct preference for oviposition by the adults on pseudostem of banana from seventh month onwards. This information helps to reduce the insecticidal load in the banana ecosystem by advocating pesticides from seventh month only. The existence of oviposition deterrency when more females were confined to Nendran pseudostem pieces revealed the deposition of spacing pheromones by conspecific females after egg laying. It was seen that the acetone and ether extracts of pseudostem pieces where ten females had laid their eggs, when sprayed on fresh pseudostem, deterred the oviposition by other females. Isolation and identification of such epidectic compounds will help in their utilisation in the field to prevent egg laying on banana pseudostem. The morphological, anatomical and biochemical bases of resistance were also identified. The morphological parameters associated with resistance were smaller width and breadth of the sheath coupled with more number of sheaths in the resistant variety. These increased the number of cuticular layers and cell walls the grub had to traverse before entering the central pith. The pith formation is of prime importance to the curculionid as it becomes the target site of feeding for third and fourth in stars. There are certain cues emanating from the pseudostem subsequent to maturity, which aids the adult weevils in host selection and oviposition. The lesser moisture and higher crude fibre content of Njalipoovan pseudostem exhibited greater influence on resistance by posing a mechanical barrier to egg laying and feeding of neonate larva. The information on moisture content is of practical utility in the management of the pest in endemic areas. It may be possible to artificially create moisture stress in the plant attaining flower bud initiation stage by regulating irrigation. The level of irrigation has to be adjusted so as not to induce a yield reduction but at the same time to induce moisture stress at least in the outer sheaths to prevent oviposition. The water suckers served as more conducive hosts for the pest even before sufficient maturity and this highlighted the need for removal of water suckers from endemic fields. The anatomical sections of pseudostem sheath clearly revealed a thick cuticle on epidermal cells with four to five layers of dense collenchymatous hypodermis imposing a physical barrier against oviposition in the resistant cultivar. Further, the ground tissues which constituted of compactly arranged parenchymatous cells with several starch grains offered feeding deterrency. The closely packed bigger sized lower epidermal cells along with additional parenchymal layers below the air cavity operated as a mechanical barrier which caused the failure of the neonate larva to penetrate inner tissues. Higher content of phenolics generally showed a positive correlation with resistance. However, the role of ortho dihydric phenolic substrates in resistance is greatly dependent on the enzymatic activity of polyphenol oxidase to form toxic metabolites like quinones and tannins. Hence, the oxidation factor of OD phenols clearly indicated the dominance of the resistant variety, Njalipoovan. The accelerated activity in Njalipoovan is endowed with greater potentiality to activate polyphenol aggressively effecting more production of lignin, quinone and tannins, in the event of egg laying or feeding by the pseudostem weevil.
Open Access
Screening medicinal plants for antihelminthic properties against different life stages of banana burrowing nematode radopholus similis [Cobb,1893] thorne 1949
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1996) Sreeja, P; KAU; Job Sathyakumar, Charles
Experiments were conducted at the department of Entomology, College of Horticulture, Vellanikkara to screen medicinal plants for antihelminthic properties against the infective stages of banana burrowing nematode R. similis. The effect of aqueous extract of different parts of 20 medicinal plants were treated at four dilutions and three exposure times. Nematicidal and nematostatic properties of these extracts were studied using the nematode culture developed on carrot callus. The study resulted in the following findings. 1. Extracts of A. indica and G. pentaphylla were highly nematicidal to infective stages of the nematode at all the tested doses. K. pinnata was significantly effective at all the tested doses except 1:40. P. longum resulted in significant mortality at all the tested doses against larval stages whereas only 1:5, 1:10 and 1:20 dilutions were effective against adult stages. Besides nematicidal effect 1:20 and 1:40 dilutions of G. pentaphylla and K. pinnata exhibited nematostatic effects. 2. Leaf extract of M. oleifera and M. piperita at 1:5 and 1:10 dilutions showed significant nematostatic effects against both larvae and adults. P. betle extract was equally effective at the three dilutions. 3. Leaf extracts of C. angustifolia, A. squamosa and L. inermis were not effective at all tested doses. 4. Fruit extract of M. azedarach was nematicidal at all the tested dilutions of 1:5, 1:10, 1:20 and 1:40. But extract of C. papaya was ineffective. 5. Seed extract of C. viscosa expressed nematostatic property at 1:5 and 1:10 dilutions against adult stages, but it was ineffective against larval stages. Treatment with seed extract of E. scandens was ineffective. 6. Rhizome extract of C. rotundus was equally effective against infective stages in causing mortality at 1:5, 1:10 and 1:20 dilutions. Besides nematicidal effects, the extract exhibited significant nematostatic effect. A. calamus extract was nematostatic at 1:5 and 1:10 dilutions. 7. Root extract of I. tinctoria was nematostatic at 1:5, 1:10 and 1:20 dilutions against both larvae and adults. In addition to immobility, it resulted in the death of adult nematodes at 1:5 and 1:10 dilutions. Extract of S. indicum showed significant nematostatic effect at 1:5, 1:10 and 1:20 dilutions against larval stages. But it was effective only at 1:5 and 1:10 dilutions against adult stages. 8. Plant extract of E. hirta expressed nematicidal property at 1:5, 1:10 and 1:20 dilutions against larval stages, but the same was effective only at the two lower dilutions against adult stages
Open Access
Evaluation of the active principles of the rhizome extracts of L. for the management of melon fly
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1996) Shakunthala, Nair; KAU; Jim, Thomas
The melon fruit fly Bactrocera cucurbitae : Diptera) is one of the highly destructive pest species attacking cucurbits. The larvae hatching from eggs deposited within the fruits, tunnel and feed on the internal contents. As a result of this, the fruits are severely damaged, rot and fall to the ground, where pupation takes place. As the recommended management practices against the melon fly are still proving inadequate, there is a need to devise newer and safer means to solve this problem. The latest trend in pest control is the use of natural products derived from plant and animal sources. Among the various plants tested, Acorus calamus L., is gaining importance owing to its insecticidal and insectistatic properties. The present study was carried out at the Department of Agricultural Entomology, College of Horticulture, Vellanikkara, during 1993-94, with the objective of evaluating the extracts of A. calamus for the management of the melon fly, B. cucurbitae. The experiments were conducted in order to assess effects like repellency, feeding deterrency, oviposition deterrency, ovicidal action, topical contact toxicity to larvae, pupae and adults and chemosterilant action. Water and organic solvents were used to prepare the A. calamus extracts. Among the organic solvents tested, methanol was selected, owing it’s the better effect. Melon flies (B. cucurbitae ) reared in the laboratory were used for all the tests, and the following results were obtained. The repellent and feeding deterrent effects of the extracts was proved by reduced alightment of flies on the treated substrates. The aqueous extracts were effective at 5%, while the methanol extract at 0.1% was highly repellent., proving the superiority of the methanol extract. In the oviposition deterrency test, the number of ovipunctures as well as the fecundity realization, showed a decreasing trend with the increase in concentration of the extracts. The methanol extract was found to be superior to the aqueous extract in deterring oviposition also, as it was effective at 0.25 %, while in case of the aqueous extract a significant effect was produced only at a concentration of 5 %. Toxicity tests were conducted on all life stages of the melon fly. The eggs were not affected by the aqueous extract upto 10%, but there was 100% egg mortality (inhibition of hatching) when 0.1% methanol extract was used. The LC50 of methanol extracts to the eggs was found to be 0.03%. Both the aqueous extract and the methanol extract were found to be ineffective in causing mortality to larvae and pupae, upto 10%. In the case of adult flies, there was no mortality upto 10% of the aqueous extract by topical application or residue film technique. Topical application with methanol extract could not be followed, as the solvent itself caused 100% mortality. However by residual film application, it was possible to obtain a range of mortalities, and the LC50 of methanol extract to adult flies was found to be 0.07%. The methanol extracts were found to inhibit mating completely, in adult flies fed with the extracts at 0.1 to 0.01 % from the day of emergence. The average survival period of these flies was also significantly lower, because of which, fecundity realization was not see. The sizes of reproductive organs in the treated flies were found to be considerably reduced, probably due to regression or oosorption in the ovaries, or general atrophy of the organs, caused by the feeding of the extracts. This damage to the reproductive organs might have caused a hormonal imbalance, which resulted in the mating being inhibited
Open Access
Biocontrol of pests of vegetable cowpea (Vigna unguiculata sub sp. sesquipedalis (L.) verdcourt)
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1997) Bindu, S S; KAU; Sudharma, K
Monitoring of the incidence of pests and their natural enemies was carried out in the heavily insecticide sprayed vegetable cowpea plots in farmers' fields in two locations viz. Kalliyoor and Palappur in Thiruvananthapuram District and in the unsprayed crop raised in the Instructional Farm, College of Agriculture, Vellayani, during kharif and rabi, 1996. The results of the monitoring revealed that the pea aphid, A. craccivora , the pod bugs R. pedestris and C. gibbosa and the pod borers H. armigera, L. boeticus and M. testulalis were the major pests that attacked vegetable cowpea both in the insecticide sprayed as well as in the unsprayed plots. The pea aphid was persistent in the insecticide sprayed fields where as in the unsprayed fields, they were not seen upto 35 days after sowing, in both kharif and rabi season. The pod bugs and pod borers were seen throughout the cropping period with increase in the post flowering period in both sprayed and unsprayed crop. Attack of the american serpentine leaf miner L. trifolii was observed only in the insecticide sprayed fields and was present in rabi as well as in the kharif seasons The parasitoids that were encountered were A. nigrotibiali$, Charops sp., Salius sp. and T. subvirescens and the predators were M. sexmaculatus, M. crocea, Scyanus sp., E. stali, S. geminate and X. scutellarae. The population of the natural enemies was higher during the rabi season than that during kharif season. The population of the pests and natural enemies in the insecticide sprayed and unsprayed plots were compared using students ‘t' test and the results revealed that the pest were more in the un sprayed plots but the population was higher only for a shorter period and it was effectively checked by the natural enemies, the population of which synchronized with that of the pests. There was significantly higher population of natural enemies in the unsprayed plots when compared to unsprayed plots. The role of the green lacewing C. carnea in the management of the vegetable cowpea pests was studied through replicated field trials conducted at College of Agriculture, Vellayani during 1996. The impact of biorationals viz., neem oil and tobacco decoction and insecticide, malathion on the predator C. carnea and in their effectiveness in management of cowpea pests was also studied in the field experiment. C. carnea released @ 50 per plot at fortnightly intervals effectively checked the aphid population. Among the botanicals, tobacco decoction 2 per cent was found to be effective in controlling the aphids, pod bugs and pod borers. Neem oil emulsion 10 per cent when applied at fortnightly intervals was also found to be significantly superior to the untreated control. However the infestation by aphids and the pod bugs was' less in all the treatments when compared to control. Though the control plot did not show significant reduction in yield, the quality of the produce was reduced due to the pest infestation. C. carnea @ 100 per plot at fortnightly and monthly intervals were effective against pod bugs. The pod borers were effectively checked by C. carnea • 50 arid 100 per plot. In general the monthly release of C. carnea was comparatively less effective in controlling the pests. The botanicals did not show any deleterious effect on C. carnea. When the yield was assessed in terms of weight and number of pods harvested, significantly higher yield was recorded only in plots treated with tobacco decoction 2 per cent when compared to untreated control.

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