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Open Access
Major spiders in vegetable ecosystem and their predatory potential
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Manu Mani, P; KAU; Hebsi Bai
Spider faunistic survey conducted in okra, brinjal, cowpea, bittergourd and amaranthus fields in Kalliyoor panchayat of Thiruvananthapuram district during the summer of 2004, revealed the prevalence of high density and diversity of spiders in the vegetable ecosystem. Hunting spiders were dominant in all the vegetable plots. Thirty species of spiders distributed in nine families were recorded with the number of species in each vegetable field ranging from 10 to17. Among the thirty species, 16 species were commonly seen in the different vegetable fields while 14 species were seen exclusively associated with a particular vegetable. Araneidae with ten species was the most represented family in the vegetable fields followed by Oxyopidae and Salticidae. The other families observed were Miturgidae, Thomisidae, Tetragnathidae, Corinnidae, Lycosidae and Clubionidae. Most of the spiders appeared during the vegetative and flowering stages of the crop. Few spiders were recorded in the early stage of the crops. Four spiders viz., O. javanus, C. danieli, N. mukerjei and T. mandibulata were dominant in all the vegetable plots among which O. javanus and C. danieli predominated. Studies on the seasonal influence showed no significant difference in the abundance of the spiders during summer and rainy seasons. Rather, the growth stages of the crops significantly influenced the build up of the spider population with higher population being observed during the reproductive phase. In general, the spiders preferred soft bodied insects like the hemipterans, lepidopterans, dipterans and coleopterans (eggs and grubs) for predation. While the spiders did not show any significant preference for the different hemipteran prey in a mixed diet, significant difference was shown for the different lepidopteran pests. O. javanus had the maximum preference for the lepidopteran pests Chemical insecticides were more toxic to the spiders than botanicals when tested at their recommended doses. Among the chemical insecticides, dimethoate 0.05 per cent, carbaryl 0.2 per cent and malathion 0.1 per cent were highly toxic. Even at different doses the insecticides were toxic to the spiders. Quinalphos 0.05 per cent and imidacloprid were less toxic. Between the two methods of application, topical application of insecticides was more detrimental to the spiders than release on treated plants. Among the spiders, T. mandibulata was more susceptible to the insecticides followed by C. danieli. O. javanus and N. mukerjei were less sensitive. While the fungal pathogens, M. anisopliae, P. lilacinus and Bt were safe to the spiders. F. pallidoroseum, Fusarium sp. and B. bassiana were pathogenic. Based on the results of the study, conservation of the spiders characteristic of the vegetable ecosystem would be a practical and ecologically and economically viable approach for pest suppression in vegetables. When there is a spurt in pest ravage, the protection afforded by the predator could be supplemented with judicious use of “spider friendly” insecticides.
Open Access
Major spiders in vegetable ecosystem and their predatory potential
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Manu Mani, P; KAU; Hebsi, Bai
Spider faunistic survey conducted in okra, brinjal, cowpea, bittergourd and amaranthus fields in Kalliyoor panchayat of Thiruvananthapuram district during the summer of 2004, revealed the prevalence of high density and diversity of spiders in the vegetable ecosystem. Hunting spiders were dominant in all the vegetable plots. Thirty species of spiders distributed in nine families were recorded with the number of species in each vegetable field ranging from 10 to17. Among the thirty species, 16 species were commonly seen in the different vegetable fields while 14 species were seen exclusively associated with a particular vegetable. Araneidae with ten species was the most represented family in the vegetable fields followed by Oxyopidae and Salticidae. The other families observed were Miturgidae, Thomisidae, Tetragnathidae, Corinnidae, Lycosidae and Clubionidae. Most of the spiders appeared during the vegetative and flowering stages of the crop. Few spiders were recorded in the early stage of the crops. Four spiders viz., O. javanus, C. danieli, N. mukerjei and T. mandibulata were dominant in all the vegetable plots among which O. javanus and C. danieli predominated. Studies on the seasonal influence showed no significant difference in the abundance of the spiders during summer and rainy seasons. Rather, the growth stages of the crops significantly influenced the build up of the spider population with higher population being observed during the reproductive phase. In general, the spiders preferred soft bodied insects like the hemipterans, lepidopterans, dipterans and coleopterans (eggs and grubs) for predation. While the spiders did not show any significant preference for the different hemipteran prey in a mixed diet, significant difference was shown for the different lepidopteran pests. O. javanus had the maximum preference for the lepidopteran pests Chemical insecticides were more toxic to the spiders than botanicals when tested at their recommended doses. Among the chemical insecticides, dimethoate 0.05 per cent, carbaryl 0.2 per cent and malathion 0.1 per cent were highly toxic. Even at different doses the insecticides were toxic to the spiders. Quinalphos 0.05 per cent and imidacloprid were less toxic. Between the two methods of application, topical application of insecticides was more detrimental to the spiders than release on treated plants. Among the spiders, T. mandibulata was more susceptible to the insecticides followed by C. danieli. O. javanus and N. mukerjei were less sensitive. While the fungal pathogens, M. anisopliae, P. lilacinus and Bt were safe to the spiders. F. pallidoroseum, Fusarium sp. and B. bassiana were pathogenic. Based on the results of the study, conservation of the spiders characteristic of the vegetable ecosystem would be a practical and ecologically and economically viable approach for pest suppression in vegetables. When there is a spurt in pest ravage, the protection afforded by the predator could be supplemented with judicious use of “spider friendly” insecticides.
Open Access
Evaluation of bait application technique for the management of fruit flies infesting cucurbits
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Vidya L; Jiji T
A survey conducted in Kalliyoor and Nedinjil areas and Instructional farm, Vellayani for the assessment of pest incidence in the field revealed that among the five cucurbits viz., snakegourd, bittergourd, pumpkin, cucumber and coccinia, bittergourd had the maximum percentage incidence and coccinia the minimum. Two spiders viz., Oxyopes shweta and Oxyopes sp. and a larval pupal parasite of fruit flies viz., Opius sp. were observed in the field. From the infested fruits of these cucurbits the maximum number of flies emerged from snakegourd and the minimum from coccinia. B. cucurbitae was the only species that emerged from these infested fruits. The survey conducted in Kalliyoor and Nedinjil areas for documenting farmers’ practices showed that majority of the vegetable growing farmers cultivated cucurbits. The farmers were not following Package of Practices recommendations for spacing and fertilizer and pesticide dosages. All the farmers adopted the use of fruit fly traps, especially Palayankodan + carbofuran trap. In the screening experiment in the field, Rasakadali + jaggery + water + carbofuran, Palayankodan + boiled jaggery + water + carbofuran, Palayankodan + jaggery + water + carbofuran and Palayankodan + carbofuran were found to be significantly superior food baits with respect to total fly catch and duration of effective trap catch. In the cage experiment for selecting two superior baits out of the four baits selected from the field screening trial, Rasakadali + jaggery + water + carbofuran and Palayankodan + boiled jaggery + water + carbofuran were found significantly superior. Heating jaggery to 80oC increased the duration of effective trap catch and keeping quality of food baits. Plastic bottles of 350ml capacity provided with windows of size 6cm x 3cm was found to be the most efficient bait dispenser. In the field experiment for standardization of spacing Rasakadali + jaggery + water + carbofuran at 3.5m x 3.5m had the maximum fly catch, compared to all the other treatments. However there was no significant difference in fly catch when the same food bait was used at different spacing. The significantly lower percentage of incidence was noted when Rasakadali + jaggery + water + carbofuran was used at 2.5m x 2.5m and 3m x 3m and Palayankodan + boiled jaggery + water + carbofuran at 2.5m x 2.5m. The yield was maximum when Rasakadali + jaggery + water + carbofuran was used at 2.5m x 2.5m. The population of foliage pests in the snakegourd field was maximum during peak vegetative stage. The peak population of spiders did not coincide with peak fruit fly population. But the population of Opius sp increased with the population of fruit flies. In correlation with weather parameters it was found that female and total fruit fly population had significant negative correlation with morning relative humidity and number of rainy days. The results of the present study clearly revealed that by the adoption of improved Bait Application Technique profitable production of cucurbits without pesticide contamination is possible.
Open Access
Seasonal occurance and ecofriendly management of pests of amaranthus
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Asha, J S; KAU; Nandakumar, C
Seasonal occurrence of pests, their natural enemies and leaf blight disease of amaranthus were studied in the Instructional Farm, College of Agriculture, Vellayani from April 2004 to April 2005. Leaf webbers Psara basalis F. and Hymenia recurvalis (F.) were the major pests of amaranthus and leaf blight disease caused by Rhizoctonia solani Kuhn. was the major disease. The leaf webber P. basalis was present in the field throughout the year. However the highest population and infestation was observed during the summer months. Maximum population of larvae was observed during the month of April 2004. The population and extent of damage by the pest exhibited significant positive correlation with maximum and minimum temperature. The leaf webber H. recurvalis was also present in the field throughout the year. The population and extent of damage by the pest was maximum during June, July and November 2004 and minimum during the summer months (April and May 2004). The population of the pest showed significant positive correlation with minimum temperature. The green grasshopper Atractomorpha crenulata F. was observed in the field throughout the year. Highest population was observed during the first fortnight of October 2004. The percentage of plants and leaves damaged by the grasshopper was maximum during the second fortnight of November 2004. The population and extent of damage of the grasshopper showed significant negative correlation with minimum temperature. The percentage of plants damaged by the tobacco caterpillar Spodoptera litura (F.) was maximum during the second fortnight of June 2004 and the leaves damaged was the highest during the first fortnight of June 2004. The leaf damage showed significant positive correlation with rainfall. A solitary braconid endoparasitoid Apanteles opacus (Ashmead) was found infesting the second instar larvae of H.recurvalis. The population of pupae of the parasitoid was maximum during the first fortnight of July 2004. Spider predators viz., Oxyopes spp., Cheiracanthium sp., Phidippus sp. and Tetragnatha sp. were found in the field throughout the year. Maximum population of spiders was observed during the second fortnight of September 2004. The population showed significant positive correlation with maximum temperature. The leaf blight disease caused by R. solani was observed throughout the year. The percentage disease index (PDI) was maximum during the second fortnight of December 2004. Studies on antifeedant effect of botanicals on major pests of amaranthus revealed that azadirachtin 0.0025 per cent was the best phagodeterrent followed by cow’s urine 10 per cent + NSKE five per cent and NSKE five per cent. Six botanical pesticides were evaluated with malathion as check in a field experiment. The treatments included neem seed kernel extract five per cent (NSKE), neem cake (NC) soil application @ 250 kg.ha-1 at planting + neem cake extract (NCE) 10 per cent spray, azadirachtin 0.0025 per cent, cow’s urine 10 per cent + NSKE five per cent, Pongamia oil soap emulsion two per cent and annona seed extract two per cent. Three sprays of the treatments were applied on the crop during the experiment. The results revealed that all the treatments were significantly superior to control in reducing the population of pests and their damage. Azadirachtin 0.0025 per cent was the most effective treatment against leaf webbers and grasshopper. This was followed by cow’s urine 10 per cent + NSKE five per cent and NSKE five per cent. The extent of damage caused by these pests in azadirachtin treated plots was statistically similar to that of malathion treated plots. . The extent of damage by the tobacco caterpillar was the lowest in NC soil application @ 250 kg ha-1 + NCE 10 per cent spray treatment. Higher population of spiders was found in botanical treated plots and control plots compared to malathion treated plots. The botanical treatments were not effective in containing the leaf blight disease. Maximum yield of marketable produce was recorded from malathion treated plots. However the B : C ratio was the highest (3.20) in botanical treatment, azadirachtin 0.0025 per cent (NeemAzal 1% TS @ 2.5 ml/litre) followed by cow’s urine 10 percent + NSKE five per cent (2.12) and NSKE five per cent (2.08). Three sprays of any of these botanicals at fortnightly intervals starting from two weeks after transplanting could manage the pests of amaranthus.
Open Access
Population dynamics and management of erythrina gall wasp quardrastichus erythrinae kim.
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2008) Beena, M P; KAU; Thomas Biju, Mathew
. Studies were conducted to understand the population dynamics and management of Erythrina Gall Wasp (EGW)Quadrastichus erythrinae. An abstract of the work done and the results are given below. Population dynamics of Q.erythrinae was studied by observing weekly emergence of male and female insects from leaflets and petioles collected from field during the period from January 2006 to June 2007. The results showed that population was high in the months of July 2006, January 2007, April 2007 and June 2007.The present study indicated that the emergence od adult EGW was the highest from petioles. The increase in weight due to EGW infestation and gall production was the highest in the left lateral leaflets. Weekly mean population of EGW emerged during the period of study showed that the total number of male EGW (1096.36) was higher than the female insects emerged (763.13). Weekly mean population of the male and female emerged from the leaflets and petioles was correlated with weather parameters viz. maximum and minimum temperature. Maximum and minimum relative humidity and rainfall prevailed during the time of sampling, previous one week, previous 14 days,week 21 days before and week 28 days before. The results showed significant and positive correlation between population of male EGW and the minimum temperature, while no correlation existed between female population and other parameters studied. Comparison of biometric observation of uninfested and infested plant parts indicated that the weight of the leaflets and petioles increased significantly due to an increase in biomass. Due galling by EGW, the girth of the petioles was shortened to about one third of uninfested petioles. The emergence of EGW was maximum from petioled scored in the damage category ‘9’. Among the four groups of Erythrina stricta Roxb..stricta trees studied, based on the height of the trees, no group turned out to withstand the damage by EGW. Thiomethoxam, imidacloprid, carbaryl and acephate proved superior among the chemical tested insecticides tried against female and male EGW in the laboratory . Neem oil 2 per cent and neem oil-garlic 2 per cent proved superior among the botanical insecticides tried for protecting the newly formed side shoots. Among the systemic /translaminar insecticides applied on the galled plant parts, triazophos 0.05 per cent and imidacloprid .002 per cent were significantly superior in controlling the EGW emergence. In the field experiment conducted to evaluate insecticide-fungicide combination for EGW infestation and protection of the new side shoots, carbaryl 0.1 per cent and combination of imidacloprid 0.002 per cent and carbendazim 0.2 per cent effectively protected the side shoots up to 8 weeks after spraying. Residue analysis of dry pepper berries collected from pepper vines trailed, on the insecticide sprayed crythrina standards showed that residues at the time of harvest from trees sprayed with acephate 0.05 per cent dimethoate 0.05 per cent were below detectable limit. Where as the residues in pepper collected from lamda cyhalothrin 0.05 per cent and triazophos 0.05 percent treated trees was 1.38 ppm and 1.16ppm respectively. An overall analysis and interpretation of the data on population in relation to phenology to E.stricta foliar growth showed that there existed a six monthly cycle of damage by gall wasp resulting in complete defoliation of the trees by about six month followed by the next cycle of regrowth and re infestation .
Open Access
Bio-efficacy and molecular characterization of the native isolates of Bacillus thuringiensis Berliner
(Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 2008) Jyothi Sara, Jacob; KAU; Maicykutty, P Mathew
Bacillus thuringiensis Berliner shortly known as B.t., is a gram-positive, spore forming bacterium that produces proteinaceous crystal containing insecticidal toxins. The host range of B.t. has expanded considerably due to extensive screening programmes. By virtue of its lack of toxicity towards other species of animals and human beings, B.t. has emerged as a safe candidate in the IPM programmes of various agroecosystems. Frequent exposure to one type of B. thuringiensis toxins can develop resistance in insects. Isolation of novel strains is important to overcome the onset of insect resistance. The present study on “Bio-efficacy and molecular characterization of native isolates of Bacillus thuringiensis Berliner” was conducted at the Department of Agricultural Entomology and CPBMB, College of Horticulture, Vellanikkara during the period from 2006 to 2008 with an objective to study the pathogenicity of 20 B. thuringiensis isolates collected from the Western Ghats of Kerala, one of the well known hot spots of biodiversity. The tobacco caterpillar, Spodoptera litura Fb. which was used as the test insect was reared in semi-synthetic diet (Ballal, 2004) and also in natural diet on castor leaves. The preliminary screening was performed for lepidopteran specificity with the ideal dose of 1 x 109 spores per ml showed that three isolates were toxic to S. litura. The per cent mortality caused by the lepidopteran effective isolates, namely, KAU-11, KAU-51, KAU-166 and the reference strain, HD-1 were 76.7 per cent, 80.0 per cent, 86.7 percent, 96.7 per cent respectively. A standardized bioassay was carried out with five different concentrations of all the selected isolates namely, KAU-11, collected from Thusharagiri (Calicut Dt.), KAU-51 from Kolahalamedu (Idukki Dt.), KAU-166 from Nelliyampathi(Palakkad Dt.) and the reference standard HD-1 (B. thuringiensis subsp. kurstaki). The mortality ranged from 63.3 to 100.0 per cent in various isolates and there was no significant difference between isolates. This indicated the equal effectiveness of the native isolates with the standard strain, HD-1. The LC5o value for the isolates was calculated by Finney’s Method of Probit Analysis. The lowest LC50 was obtained in KAU-51, with 6.3095 x 104 spores per ml and highest in KAU-11, with 1.2589 x 106 spores per ml. The lethal time to cause 50 per cent mortality (LT50) ranged from 44.4 h. to 96.0 h. in different isolates. The lowest LT50 was recorded in HD-1, which shows the ability of the standard to cause mortality slightly earlier compared to other isolates. The molecular characterization of the selected isolates was performed with RAPD-PCR technique. RAPD-PCR is a simple and rapid method for determining genetic diversity in various organisms and is a means of creating a biochemical finger print of an organism. Out of the 20 primers screened, 10 primers which produced more than five bands were selected for RAPD analysis. The RAPD data was used to generate a similarity matrix using the NTSyS programme. Clustering was done and dendrogram was drawn using Unweighted Pair Group Method of Arithematic Averages (UPGMA). The results showed that high variability exists between the selected isolates. Further studies are required to identify the subspecies of the efficient B.t. isolates to evaluate the field effectiveness against S. litura and other major lepidopteran pests for its utilization in pest management programmes. More primers need to be screened to study the genetic diversity of the isolates.
Open Access
Insect pollinators of oil palm in Kerala
(Department of Agriculture, College of Horticulture, Vellanikkara, 2010) Sambath, Kumar; KAU; Ranjith, A M
Oil palm, Elaeis guineensis (Jacq.) (Arecaceae) is one of the most commonly available and extensively cultivated perennial trees in many parts of the world. Previously pollination was considered as a serious constraint, so manual pollination was often carried out, to sustain the yield. Wind and honey bees play an important role in pollination of many crops. But they alone can not give adequate level of pollination in all circumstances. In nature, pollination by specific insect species is vital for many crops. In this context, the present investigation on the “Insect pollinators of oil palm in Kerala” was carried out in the Plantation Corporation of Kerala, Athirappilly and Laboratory trails were conducted in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2009 to 2010. Fifteen different insect species were observed to visit on the inflorescence. Insect species such as, African oil palm weevil, Elaeidobius kamerunicus (Coleoptera: Curculionidae); an earwig, Forficula sp.? (Dermaptera); a moth, Pyroderces sp.? (Lepidoptera: Cosmopterigidae) and Indian honey bees, Apis cerana indica (Hymenoptera: Apidae) were main species from the collection on male and female inflorescences. Population of different insect visitors on anthesising female inflorescence was highly varied and E. kamerunicus was found to be more, among all insect species. Weevils were found to be visiting the female flowers between 10.00 a.m. to 2.00 p.m. and the peak weevil population was observed on the 1st and 2nd day of anthesis, around 12.00 noon. But, on male inflorescence weevil population was less during 10.00 to 2.00 p.m. Thereafter, it was gradually increased and attained the maximum at 4.00 p.m. Highly significant positive (r = 0.712**) correlation was observed between population of E. kamerunicus on 1st day of anthesis of female flowers and per cent pollination whereas, it was not significant (r = 0.199) on the 2nd day of anthesis which indicates that maximum amount of pollination occurred in the 1st day of anthesis. Weevils of E. kamerunicus were congregating on the male inflorescence during the entire period of anthesis and their statistical median weevil population was 48, 76, 80 and 35, 56 and 72 on top, middle and bottom portions of male inflorescence during rainy and summer seasons respectively. Adult weevils of E. kamerunicus feed on anthers of male inflorescence and multiply. Everyday, during occasional visits to female inflorescence, they would shed the pollen grains and get back to its original place of host which would cause adequate level of pollination of female flowers. The anise seed like odour (estragole 5, 4 allylanisole) attract the weevils towards both male and female inflorescences. The biology of E. kamerunicus was carried out in both rainy and summer seasons under wire cage. The female weevil laid eggs singly on the spent male inflorescence of oil palm. The fecundity ranged from 32 to 33 eggs (median = 32) in rainy and 34 to 35 eggs (median = 35) in summer seasons with an ovipositional period of 1 to 2 days during both seasons. The eggs hatched into grubs within 1 to 2 days. The grub period lasted for 8 to 10 days in rainy and 7 to 9 days in summer seasons respectively with three larval instars. The grubs pupated for 3 to 4 days in rainy and summer seasons and the adult weevils emerged out. The total life cycle from egg to adult was completed within 14 to 16 and 11 to 14 days in rainy and summer seasons respectively. The longevity of adult weevils varied with the sex and males lived longer than females. The life span of male weevils was 5 to 7 and 4 to 6 days during both rainy and summer seasons respectively. Female weevils lived for 4 to 6 days in rainy and 4 to 5 days in summer seasons. Among the duration of different life stages viz., egg, larva, pupa and adult of E. kamerunicus, the grub period was found to be longest (7 to 9 days) followed by adult longevity (male = 5 to 6 days; female = 5 days), pupa (3 to 4 days) and egg (1 to 2 days). The number of female weevils in the field was more, when compared to the male with the sex ratio (♂ : ♀) of 1 : 1.87 in rainy and 1 : 1.96 in summer seasons respectively. Morphometric study of different life stages of E. kamerunicus showed that the diameter of egg measured 0.258 mm. The freshly laid eggs were creamy white in colour. The first instar grub was pinkish yellow in colour with brown head capsule and other instars are yellow coloured. The average length of I, II and III instar grubs were 1.59, 2.73 and 3.84 mm. Similarly mean body width of corresponding instars was 0.52, 0.86 and 1.62 mm. The pupa also showed yellow colour with the length of 3.53 mm and width of 1.63 mm. The newly emerged adult weevil was light brown in colour and later on changed to dark brown. The male and female weevils could be differentiated based on their size and additional structures on their body. Males (length = 4.13 mm; width = 1.54 mm)) were bigger than female (length = 3.81 mm; width = 1.28 mm). Males also had setae on the peripheral side of elytra with some dorsal spines. Female has smaller body and absence of above mentioned structures over its body. Both male and female inflorescences were produced separately in successive whorls. Production of male inflorescence ranged from 0 to 2 from 10 different marked palm trees and at least one male inflorescence (mode = 1) could be seen in each tree from July ‘09 to Jan ‘10 except during Sep ‘09 (mode = 2). Female inflorescence production ranged from 0 to 1 during July ‘09 to Feb ‘10 except during Aug ‘09 (1 to 6) and Oct ‘09 (0 to 3). The mode value of female inflorescence production was 1 during July ‘09 and Aug ‘09 and it was zero from Sep ‘09 to Feb ‘10. Anthesis period of male inflorescence accounted for 10 to 14 days with more weevil population between 4th to 7th days which coincided with the maximum odour emission. Stigma receptivity lasted for 2 to 3 days but, insect visit was observed for only 2 days. So, assisted pollination can be done only up to 2 days of anthesis of female flowers. The bunch set was not found to be uniform in each month. The mode value of bunch set was varied in different months like 0, 1, 5, 5, 4, 6 and 2 from July ‘09 to Feb ‘10. Production pattern of male and female inflorescence with regard to different climatic factors was recorded from July ‘09 to Feb ‘10. An increasing trend of male inflorescence production was observed from July ‘09 to Sep ‘09 (mode = 2) with the maximum and minimum temperature of 29.91 and 24.28 oC, relative humidity of 94.37%, rain fall of 12.67 mm and sun shine hours of 0.52 hrs. Later on uniform production was recorded until Jan ‘10 and no inflorescence was seen during Feb ‘10. Similarly female inflorescence production was found to be uniform during July ‘09 and Aug ‘09 (mode = 1) which coincided with monthly maximum (28.4 and 29.94 oC), minimum temperature (23.45 and 24.08 oC), relative humidity (98.38 and 93.52%), rain fall (19.72 and 12.31 mm) and sun shine hours of 2.48 and 3.05 hrs. There after, it was very much reduced (mode = 0). Bunch set was low in July ‘09 which, gradually increased and reached the maximum during Jan ‘10 (mode = 6) with the weather parameters such as, maximum (32.24 oC), minimum temperature (21.7 oC), relative humidity (85.23 %), rain fall (0.18 mm) and sun shine hours (8.96 hrs). Correlation study of inflorescence production and various weather parameters showed that there was a significant positive correlation with relative humidity and rain fall and significant negative correlation with maximum temperature and sunshine hours. On the contrary, monthly bunch set showed a significant negative correlation with relative humidity. Wind could be offer only less contribution towards pollination and fruit set and, it was also not influenced by birds. Totally 336 to 800 flowers were counted from female inflorescences (mean = 596.4) and the range of fruit count was from 186 to 583 (mean = 393) with 27 to 132 partially developed fruits (mean = 73.8) per bunch. Per cent pollination was from 60.36 to 88.37 (mean = 77.13 %). It took around 145 to 161 days for the complete development of fruits (mean = 153.3) and the bunch weight was 5 to 29 kg (mean = 17.13) with a mean fruit weight of 32.52 g per bunch. Observations on period of stigma receptivity of female inflorescence and time of weevil visit to female flowers may be helpful to the farmers when they would need assisted pollination either manually or through artificial means by using E. kamerunicus. The present study showed that, they can restrict the pollination just for 2 days after anthesis which will ultimately save labour, money and time spent on this. Artificial culturing of weevils can be done with kairomones to maintain their population during summer season since, very poor inflorescence production was noticed during summer. It is also necessary to retain the male inflorescence at least for one month after anthesis. This will help for multiplication of weevils. During rainy months, the spent inflorescence must be removed within 40 to 45 days to avoid disease occurrence
Open Access
Insect fauna on coconut (cocos nucifera L. ) spadix and effect of pesticides on major pollinators
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2006) Shaiju, Simon; KAU; Devanesan, S
An investigation was carried out to document the different insect species visiting the coconut inflorescence, to find out the variations in the foraging activity of different insect species and to assess the relative safety/toxicity of some commonly used pesticides to honeybees. The study revealed that the coconut inflorescence attracted thirty different species of insects towards it. These insect species visited the inflorescence to feed on either pollen or nectar or both. Bees viz., Apis dorsata, A. mellifera, A. cerana indica, Trigona iridipennis, Braunsapis sp and Eupetersia sp were found to collect both pollen and nectar of which A. mellifera and A. cerana indica dominated. Bees were found to forage on the inflorescence throughout the day and exhibit a peak period of activity during 0900 h in case of A. mellifera and A. cerana indica and during 1200 h in case of T. iridipennis. All these species of bees exhibited two distinct peaks during the day of which the second peak was during 1500 h. They mainly collected pollen from half opened male flowers. Ant species that foraged on the coconut inflorescence in large numbers were Solenopsis geminata, Myrmicaria brunnea, Dolichoderus sp, Camponotus sericeus. They visited the inflorescence for feeding pollen and nectar. The population of ants remained more or less same throughout the day, they visited in higher numbers during 0900 h. They were present on the inflorescence throughout the day and maximum during 0900 h. Other insect species that visited the palm inflorescence were flies (Bactrocera cucurbitae, B. dorsalis, Musca domestica, Hemipyrellia sp., Graptomyza brevirostris and Sarcophaga sp.), wasps (Polistes hebraeus, Chalybion bengalense, Ropalidia variegata, Vespa cincta and Vespa sp.), beetles (Oxycetonia versicolor and Oxycetonia sp.) and moths (Euchromia polymena and Melanitis leda ismene). The maximum population of insects was observed on the 13th day of the male phase and in the female phase it was on the second day. The population fluctuations recorded over a period of one year showed that the occurrence of bees were the highest followed by the population of ants. Bees exhibited a significant positive correlation with maximum temperature and negative correlation with relative humidity and rainfall. The results on the evaluation of pesticides for their safety/toxicity to different species of honeybees indicated that all the chemical pesticides were toxic to honeybees. Carbaryl 0.1 per cent was the most toxic while endosulfan 0.05 per cent was the least toxic chemical. However, both azadirachtin 0.004 per cent and neem oil garlic emulsion 2.0 per cent were the safest treatments to honeybees under laboratory conditions.
Open Access
Bioecology and management of mulberry leaf roller diaphania pulverulentalis(hampson)(lepidoptera: pyralidae)
(Department of Entomology, College of Horticulture, Vellanikkara, 2005) Ramalakshmaiah, C; KAU; Jim, Thomas
Investigations were carried out on the “ Bioecology and management of mulberry leaf roller, Diaphania pulverulentalis (Hampson) (Pyralidae : Lepidoptera ) simultaneously in the department of Entomology, College of Horticulture, Vellanikkara and in Kottat village of Chalakkudy area of Thrissur district during April 2004 to March 2005. The objectives of the study were to find out the biological aspects of leaf roller namely, fecundity, duration of each life stage, number of larval instars as well as bioecological aspects like identification of collateral hosts, natural enemy complex and the correlation of weather parameters on leaf roller incidence and also the pest management issues like population counts at before and after treatments and per cent leaf damage per harvestable shoot. Relative humidity at morning and evening was negatively correlated to larval population and shoot damage in both the open and intercropped system of cultivation. Photo phase showed significant positive relation on larval population in open and intercropped system of cultivation. Precipitation showed significant negative correlation on the larval population in the intercropping system of cultivation. The number of larvae per plant and shoot damage varied from month to month on mulberry. The number of larvae per plant was 1.56 in June, ascended to 5.37 by December. It came down to 1.47 in the following March in open system of cultivation. The number of larvae per plant was 1.94 in June, ascended to 7.26 by December. It came down to 2.25 per plant by the following March in intercropping system of cultivation. The shoot damage increased from 37.13 (June) to 72.83 (December). It came down to 36.96 by the following March in inter cropped system of cultivation. The shoot damage ascended from 28.5 (June ) to 75.83 (December). It came down to 45.46 per cent by the following March in open system of cultivation. The biological studies on the leaf roller revealed that the fecundity was 157 eggs with a range of 117 to 211eggs per female. The biological studies in peak season (October to December) recorded the egg period as 4 days, individual larval periods as 1.714, 2.5, 3.214, 3.28 and 3.92 days for the I, II, III, IV and V instar larvae respectively. The pupal period was 7.95 days, the adult male longevity was 8.15 days and the adult female longevity as 10.225 days. The biology in lean season (February – March) recorded the incubation period of egg as 3.3 days, individual larval periods as 1.516, 2.009, 2.471, 2.52 and 3.5 days for I, II, III, IV and V instar larvae respectively. The pupal period was 7.95 days. The adult male longevity was 8.15 days and female longevity was 10.225 days. The total development period varied from 23.25 days during the lean season to 28.01 days during peak season. There are many natural enemies affecting different life stages of leaf roller. Bracon hebetor, Chelonus sp. and a mermithid nematode parasitizes the larvae. Tetrastichus howardi attacks the pupae. The spiders Tetragnatha sp. and Philodromus sp. predated on the leaf roller. The experiments on the collateral hosts showed that the existing weed flora in and around mulberry garden, were not the hosts of leaf roller. The leaf roller did not feed on the leaves of related plant species to mulberry like Jack, Hibiscus and Cucurbits. The evaluation of different management practices against leaf roller showed that the integration of the practices like clipping of top leaves, inert soil dust application and the application of dichlorvos 0.1 per cent as the best treatment than the individual treatments concerned for the reduction in larval population and shoot damage. The management practices were not pronounced in summer season (February to April). The results were almost similar in open, intercropped system of cultivation. The chemical treatment with dichlorvos at 0.1 per cent afforded greater reduction in pupal population than other treatments. Dichlorvos exhibited greater ovicidal action by recording the hatchability of 43.33 and 16.67 per cent at 0.1 and 0.2 per cent concentrations respectively. The probit analysis if dose mortality response of dichlorvos at different concentrations showed that 1.73 per cent as the LC50 value. The time mortality response of dichlorvos at 0.1 per cent showed that 17.12 hours as the LT 50 value. The experiments on food consumption and utilization indices recorded that the approximate digestibility (AD), efficiency of conversion of ingested food into body tissue (ECI) and the efficiency of digested fool into body matter (ECD) were 53.3, 37.34 and 25.23 per cent respectively.

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