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20173
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Subject: Entomology × End date: 2017 × Start date: 2017 × Type: Thesis × Thesis Type: M.Sc ×
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    Diversity of natural enemies and efficacy of biopesticides for the management of Bemisia tabaci (Gennadius) in Bt cotton
    (Punjab Agricultural University, Ludhiana, 2017) Khangura, Samreet Singh; Rabinder Kaur
    The studies on "Diversity of natural enemies and efficacy of biopesticides for the management of Bemisia tabaci (Gennadius) in Bt cotton" were conducted during Kharif, 2016. The population of whitefly and its natural enemies were comparatively less in sprayed field as against unsprayed fields at Abohar and Muktsar. Among natural enemies of whitefly, Chrysoperla zastrowi sillemi, spiders and coccinnellids were observed in both sprayed and unsprayed fields. Diversity of natural enemies associated with whitefly in the cotton ecosystem was quite less without dominance of any particular specie. Under net house conditions, Neem oil 1 per cent @ 700 and 500 ml/acre (27.11 to 74.43 per cent reduction over control) was most effective in reducing number of nymphs of B. tabaci. It was followed by Metarhizium anisopliae @ 1200 g/acre (27.06 to 58.38 per cent reduction over control). Neem oil 1 per cent @ 700 and 500 ml/acre (32.00 to 67.54 per cent reduction over control) proved to be highly effective in minimising the population of whitefly adults under net house conditions, followed by M. anisopliae @ 1200 g/acre (23.71 to 51.01 per cent reduction over control). In field conditions, the order of efficacy of biopesticides in case of B. tabaci nymphs Neem oil 1 per cent @ 700 and 500 ml/acre (53.95 to 94.61 per cent reduction over control) ˃ M. anisopliae @ 1200 and 1000 g/acre (13.41 to 79.99 per cent reduction over control) ˃ Beauveria bassiana @ 1200, 1000 and 800 ml/acre (12.26 to 77.20 per cent reduction over control) and the order of efficacy of biopesticides in case of B. tabaci adults was Neem oil 1 per cent @ 700 and 500 ml/acre (53.12 to 95.05 per cent reduction over control) ˃ M. anisopliae @ 1200 g/acre (13.15 to 70.04 per cent reduction over control). It was concluded that Neem oil 1 per cent @ 700 and 500 ml/acre and fungal formulations (B. bassiana, M. anisopliae) being safer than chemical insecticides could be included in the IPM of whitefly in the Bt cotton in field condition.
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    Bee pollination requirement and honey production potential of broccoli (Brassica oleracea var. italica Plenck) and turnip (Brassica rapa var. rapa L.)
    (Punjab Agricultural University, Ludhiana, 2017) Shamsher Singh; Jaspal Singh
    The studies on the „Bee pollination requirement and honey production potential of broccoli (Brassica oleracea var. italica Plenck) cultivar Palam Samridhi at Punjab Agricultural University (PAU), Ludhiana and University Seed Farm (USF) Ladhowal, and of turnip (Brassica rapa var. rapa L.) cultivar L-1 at PAU, Ludhiana and USF, Nabha revealed that out of total 13 flower visiting insect species recorded on both the crops, 69.7-70.2 per cent were Hymenopterans, predominantly Apis spp. and these were the most abundant during noon. On broccoli, the foraging intensity of the honey bees was in the order of Apis mellifera>Apis cerana>Apis dorsata>Apis florea while the foraging rate was in the order of A. cerana>A. mellifera>A. dorsata>A. florea. Mean pollen gathering A. mellifera, A. cerana, A. dorsata and A. florea bees ranged between 15.6-34.9, 10.3-22.2, 15.5-31.4 and 15.7-23.2 per cent, respectively. The mean proportion of top foragers was in the order of A. dorsata>A. mellifera>A. cerana>A. florea. The highest mean number („000) of loose pollen grains (17.7) was recorded from A. dorsata followed by that from A. mellifera (14.5) and A. cerana (12.6) at 0900 h while on A. florea (6.8) at 1100 h. Pollination of broccoli by A. mellifera resulted in 359.5 siliquae per plant, 10.5 seeds per siliqua and 3.1 quintal seed yield per hectare whereas there was no siliqua and seed setting under exclusion of pollinators. Five visits of A. mellifera resulted in the highest seed weight per siliqua i.e. 29.4 mg while it was nil when there was no bee visit. A. mellifera was ranked as the most efficient pollinator on the basis of its highest pollination index (3.48) while pollination efficiency of A. mellifera was 16.9. Pollination requirement of broccoli was worked out to be one 10 bee-frame A. mellifera colony per hectare. Mean quantity of nectar production was 560 μg per 25 flowers and the mean sugar concentration of the nectar was 20.6 per cent. Honey production potential of broccoli was 4.0 kg per ha. On turnip, the foraging intensity of the honey bees was in the order of A. mellifera>A. cerana>A. dorsata>A. florea while the foraging rate was in the order of A. cerana>A. mellifera>A. dorsata>A. florea. Mean pollen gathering A. mellifera, A. cerana, A. dorsata and A. florea bees ranged between 16.9-33.8, 10.5-21.3, 16.632.7 and 15.7-23.2 per cent, respectively. The mean proportion of top foragers was in the order of A. dorsata>A. mellifera>A. cerana>A. florea. The highest mean number („000) of loose pollen grains (9.4) was recorded from A. dorsata followed by that from A. mellifera (8.4) and A. cerana (8.0) at 0900 h while on A. florea (3.6) at 1100 h. Pollination of turnip by A. mellifera resulted in 84.5, 44.9 and 263.6 per cent increase in the number of pods per plant, number of seeds per pod and seed yield over exclusion of pollinators. Five visits of A. mellifera resulted in the highest seed weight per pod i.e. 25.9 mg while it was 5.9 mg when there was no bee visit. A. mellifera was ranked as the most efficient pollinator on the basis of its highest pollination index (3.50) while pollination efficiency of A. mellifera was 20.8. Pollination requirement of turnip was worked out to be one 10 bee-frame A. mellifera colony per 2 hectares. Mean quantity of nectar production was 435 μg per 25 flowers and the mean sugar concentration of the nectar was 39.1 per cent. Honey production potential of turnip was 3.5 kg per ha.
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    Ovipositional preference and biochemical interaction of whitefly, Bemisia tabaci (Gennadius) with Gossypium species
    (Punjab Agricultural University, Ludhiana, 2017) Sukhdeep Kaur; Pandher, Suneet
    The present investigation, “Ovipositional preference and biochemical interaction of whitefly Bemisia tabaci (Gennadius) with Gossypium species” was conducted at Punjab Agricultural University Regional Research Station, Faridkot during the year 2016-2017 with three cultivars of Gossypium arboreum and G. hirsutum under multiple and no choice conditions. The results showed significant difference among Gossypium species in terms of settling of whitefly adults and fecundity per unit area. The maximum number of adults per leaf was observed on G. hirsutum var. F 2228 followed by G. arboreum FMDH 9 and FDK 124.Whitefly preferred G. arboreum var. FMDH 9 for oviposition as indicated by results followed by G. hirsutum var. F 2228, significantly different from each other. The minimum number of eggs was observed on G. arboreum var. FDK 124. The trichome density of 13.67 per five mm diameter leaf disc was the highest on the F 2228. Development time on FDK 124 was 19.79 days whereas in case of F 2228, it was 15.5 days. In the second experiment on insecticide induced resurgence, studies indicated that decline in predator population led to upsurge in Bemisia incidence for short period followed by little decline. This decline probably corresponded to eventual reestablishment of natural enemies depending on the persistence of the insecticide in the environment. Total sugars in Fipronil 5 SC treatments were significantly different at different days after spraying as compared to sampling done before first spray and corresponded with maximum resurgence of whitefly in these plots. Increase in total sugars was found in other treatments also with lesser per cent of resurgence but increase was not significantly different from initial sampling. Further, the surveys were conducted in the cotton growing areas of districts Faridkot and Muktsar at fortnightly interval from July 2016 to April 2017. Nearly thirty weed species belonging to different families were abundantly found during cotton season and off season. Ten weed species exhibiting variable symptoms showed positive results by molecular diagnostic technique (Polymerase chain reaction).The six samples were asymptomatic and also carrier of virus during off season. Two weed species Abutilon theophrasti and Achyranthes aspera having nymphs was not the carrier of virus. Twelve species of weeds neither having nymphs nor the virus, were regarded as the casual hosts of whitefly. Among the three weeds Verbesina encelioides, Solanum nigrum and A. theophrasti the total life cycle of male and female of whitefly was highest on Abutilon theophrasti which might be due to longer egg incubation period, first instar duration and adult female longevity.