Search

Experiments were carried out in the farmer’s field at Jorhat during 2015-16 and 2016-17 to study the population dynamics of red ant Dorylus orientalis Westwood in potato crop. The incidence of D. orientalis was observed both under flood free/ and prone conditions in three villages each, during potato growing season. These data were correlated with weather factors. The effect on population buildup was studied with observations at fortnightly interval starting from 1st fortnight of October to 2nd fortnight of February through fixed plot surveys. The observations revealed that maximum incidence (36.5, 33.2 and 30.1; 35.2, 32.5 and 29.8/ pit) was observed in Charaibahi, Karangia and Hokai Khangia villages, respectively during the 1st fortnight of January. In contrast, in the flood prone villages, incidence was observed to be negligible. Correlation coefficients of incidence with weather factors revealed that minimum temperature, soil temperature (morning and evening) and evaporation rate show a significantly negative correlation; whereas relative humidity (RH) (morning and evening) exhibited significant positive correlation in flood free villages. In flood prone villages minimum temperature as well as morning soil temperature showed significant negative correlation (2015-16); in contrast, in flood prone villages, RH (morning and evening) showed significant positive correlation (2016-17).

Field experiments were conducted at Charaibahi village, Jorhat, Assam during 2015-17 to evaluate six ecofriendly IPM modules against red ants Dorylus orientalis Westwood in potato. Among the modules evaluated, Module-II (pre sowing treatment of mustard oil cake @ 150 kg/ ha+ wood ash 150 kg/ ha+ panchagavya @ 3% and soil drenching with neem oil @ 5 ml/ lit after 1st and 2nd earthing up (25 and 60 DAS) recorded the lowest tuber damage both in weight (8.65%) and number (10.70%) basis and found at par with the recommended package of practices (RPP) (application of malathion 5% dust @ 40 kg/ ha+ mustard oil cake @ 150 kg/ ha in the soil after 1st and 2nd earthing up) recording 8.18 and 10.20% tuber damage, respectively. The same module also recorded highest tuber yield (119.37 q/ ha) which was at par with the RPP (120.12 q/ ha). The maximum benefit cost ratio (1.41) was recorded in RPP followed by Module-II (1.33) and Module-VI (1.26). The untreated control plot registered a very high level of tuber damage (25.93 and 28.70 on weight and number basis, respectively) having maximum population of red ants (3.95 numbers/ m2 ) with a tuber yield of 89.91 q/ ha.

Achatina fulica Bowdich is one of the most notorious pests in crop fields. However, the mucin secreted by this terrestrial mollusc has magnificent pharmaceutical attributes. In the present study, solvent and mechanical methods were explored to find out the best method of mucin extraction from this gastropod pest under laboratory conditions. In case of both medium and large sized snails, dichloromethane registered the maximum (2.79 ml and 2.94 ml, respectively) mucin collection out of the six solvents tested. Volume wise comparison showed that the maximum amount of mucin recovery was possible in the highest volume (3 ml) of solvents applied for both the age groups. Of all the mechanical methods tested, smoking method yielded maximum (2.05 ml and 3.02 ml) amount of mucin from both medium and large sized snails, respectively. However, the minimum mucin recovery was registered when the snails were allowed to move over rough tiles.

Land use change has a great impact in determining the diversity patterns of soil fauna. Adoption of any land use pattern significantly affects the soil structure and its physico-chemical characteristics, which often leads to the loss of biodiversity. Considering the collembolans as the key organism in the indicator shopping basket of soil environment, the response of Collembola communities under three different land uses represented by forest, vegetable and tea ecosystems was studied. Collembolans were sampled at monthly intervals using Tullgren funnel and identified by standard taxonomic keys. Diversity analysis and soil chemo-edaphic factors were studied to establish the impact of different land uses on Collembola communities. Five genera of Collembola viz., Cyphoderus, Entomobrya, Isotoma, Folsomia and Hypogastrura were recorded from the forest ecosystem whereas Folsomia was completely absent in vegetable ecosystem and the tea ecosystem soil was devoid of both Folsomia and Hypogastrura. Seasonal diversity and density of Collembola were recorded to be higher in the forest ecosystem indicating the presence of relatively stable habitats as compared to vegetable and tea ecosystems showing relatively disturbed habitats. Correlation studies between different chemo-edaphic factors and collembolan population revealed that the moisture and organic carbon content of soil had significant positive correlation during all the four seasons in all the ecosystems studied. Higher adoption of mechanical and chemo-centric agriculture depletes the available resources of the soil and makes it less habitable and conducive for the growth and sustenance of collembolans in vegetable and tea ecosystem as compared to forest. Appropriate landscape planning, land management strategies and developing proper methods of land use practices may pave the way for the improvement of collembolan diversity at landscape level.

Background Entomopathogenic nematodes (EPNs) are one of the widely studied biological control agents. The present study was conducted to evaluate the efficacy of two EPNs species, Heterorhabditis bacteriophora (Poinar) (Rhabditida: Heterorhabditidae) and Steinernema aciari (Qui, Yan, Zhou, Nguyen and Pang) (Rhabditida: Steinernematidae), isolated locally from soils of Majuli river island, Assam, India against two important subterrenean pests; Odontotermes obesus (Rambur) (Isoptera: Termitidae) and Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) under laboratory conditions. Results In case of O. obesus, mortality percent was recorded by H. bacteriophora after 72 h. at 300 IJs/termite and by S. aciari at 250 and 300 IJs/termite after 96 h. The lowest LD50 and LT50 values obtained for H. bacteriophora were 13.054 IJs/termite and 26.639 h., respectively, while those of S. aciari were 42.040 IJs/termite and 31.761 h., respectively. With respect to A. ipsilon, H. bacteriophora registered a highest mortality rate at 300 IJs/larvae after 144 h. S. aciari showed 100 percent mortality at 300 IJs/larva after 168 h. The lowest values of LD50 and LT50 for H. bacteriophora were 35.711 IJs/larva and 83.050 h., respectively. The lowest values of LD50 and LT50 for S. aciari were 71.192 IJs/larvae and 97.921 h., respectively. Overall, H. bacteriophora displayed more virulence toward O. obesus and A. ipsilon than S. aciari. Conclusion Both native EPNs were found effective against O. obesus and A. ipsilon. However, H. bacteriophora was more virulent toward O. obesus and A. ipsilon than S. aciari under the laboratory conditions.

Field studies were conducted to know the relationship between different tillage practices and the existence as well as depth of beetle holes of Lepidiota mansueta in some selected endemic villages. The results revealed that the maximum number of beetle holes (13.91–15.94/sq.m.) were recorded in the areas where no tillage operations were carried out and kept as uncultivated land followed by conventional tillage by bullocks (8.64–9.67/sq.m.) and tillage operation done by power tillers (4.59–5.69/sq.m.). Minimum number of holes (3.16–3.67/sq.m.) was found in areas where tillage operation was performed by the tractors. There was no significant differences observed (P = 0.05) in terms of depth of beetle holes in soil irrespective of the tillage operations conducted.

Proximate and elemental compositions of five soil-dwelling scarabs, Lepidiota mansueta Burmeister, Lepidiota albistigma Burmeister, Xylotrupes gideon (Linnaeus), Catharsius molossus (Linnaeus), and Sophrops iridipennis (Brenske), were assessed. Nutrient content varied widely, and the ranges of proximate contents were as follows: moisture (2.04–2.55%), crude protein (68.54–79.33%), crude fat (4.00–5.50%), crude fibre (5.16–8.28%), total mineral (0.80–4.98%), and carbohydrate (5.28–11.84%). Caloric content was greater in L. mansueta (379.29 kcal) compared to the other four species. The caloric contents of X. gideon (375.54 kcal) and C. molossus (375.19 kcal) were at par but significantly higher than those of L. albistigma (371.04 kcal) and S. iridipennis (361.55 kcal). Sodium content ranged 23.16–35.91 mg/100 g; potassium 14.20–44.33 mg/100 g; calcium 23.33–33.37 mg/100 g; iron 1.41–37.05 mg/100 g; copper 2.01–16.13 mg/100 g; zinc 2.38–15.86 mg/100 g; and manganese 1.09–19.66 mg/100 g. The phenol, flavonoid, and antioxidant activities of L. mansueta and L. albistigma were 4.00 and 6.42 mg catechol equivalent/g, 1.59 and 3.71 mg quercetin equivalent/g, 22.60, and 28.20%(DPPH activity), respectively. Tannin content was higher in L. albistigma (13.30 mg/g) than in L. mansueta (3.24 mg/g). Based on our study, these scarab species can be explored as food supplements and nutraceutical resources in ensuring food security.

Giant African snail ( Achatina fulica Bowdich) belongs to the Phylum-Mollusca and Class- Gastropoda. It is known for its destructive nature on cultivated crops wherever it occurs and is one of the world's largest and most damaging land snail pests. The pest is an East African origin, has spread in recent times by travel and trade to many countries. They now widely distributed and no longer limited to their region of origin due to several factors viz., high reproductive capacity, voracious feeding habit, inadequate quarantine management and human aided dispersal. A. fulica can cause serious economic damage on different crops and extensive rasping (scrapping), defoliation, slime trials, or ribbon like excrement is signs of infestation. In recent times, severe outbreak of this pest has been noticed due to some desirable agricultural and gardening practices like minimum tillage practices and straw retention techniques which help in survival of snails and make seedlings more susceptible to damage. This review paper aims to enlighten on taxonomy, distribution, extent of damage, morphology, biology, ecology, homing behaviour, seasonal incidence, nature of damage, host plants of A. fulica and its ecofriendly management strategies.

Fourteen pigmented hill rice cultivars along with a non-pigmented one were studied for ascertaining the extent of their nutritional and genetic diversity. Moisture contents of the fourteen pigmented hill rice cultivars ranged from 7.49 to 10.10 % along w.ith the contents (% dry weight) of nutrients viz., crude fat (4.37 – 5.27) and crude protein (9.27 - 11.42). The corresponding range of values for the contents (mg/100g dry weight) of microminerals Zn and Fe were form 3.42 to 4.28 and from 3.21 to 4.18 respectively. The pigmented germplasm had anthocyanin content (mg cyanidine 3-O glucoside /100g) ranging from 3.58 to 7.86, total phenolic content (mg GAE/100 g)from 67.89 to 89.43, flavonoid content (mg QE/100g)from 57.75 to 78.74 and antioxidant activity from 19.56 to 29.29 %. Analysis of variance indicated that the varietal effect on each of the parameters studied was highly significant. There was significant correlation amongst the different parameters of the rice genotypes analysed. Results of the biochemical screening of these cultivars may lead to selection of promising candidates that can be used for developing improved lines in future breeding programmes.

Population of Lepidiota albistigma grubs were estimated in five selected ecosystems of lower Brahmaputra valley of Assam during 2015–17. The study revealed that significantly more grubs were collected from grassland near water sources (8.52 ± 0.97, 7.56 ± 0.59 and 8.72 ± 0.91), followed by open grassland (4.96 ± 0.75, 5.06 ± 0.82 and 4.60 ± 0.89) and cultivated field near water sources (2.74 ± 0.83, 2.38 ± 0.92 and 2.54 ± 0.86) during 2015, 2016 and 2017, respectively. Existence of grubs in soil depth measured during April, 2015 to March, 2016 in grassland and cultivated fields revealed that maximum grubs confined up to 20 cm. Population estimation of growth stages from March, 2016 to February, 2017 revealed that adults appeared in March (0.4 A) with maximum during April 2016 (1.6 A). Grubs appeared from May (1.6 G), 2016 to January (0.6 G), 2017. Similar population of grubs (1.6 G) were recorded in May, July and September and peak population was observed in August 2016 (3G); pupae were observed in March (1.2 nos), April 2016 (0.8 nos), and February (1.4 nos) in 2017. Soil moisture studies revealed that it was maximum in April (27.63%) followed by July (24.38%) and October (24.32%). Correlation coefficients between grubs and sand (r =-0.693) and silt content (r =-0.845) were significant and negative, in contrast to the clay content (r = 0.839). Soil organic matter content (r = 0.901) and available nitrogen (r = 0.963) revealed significant positive correlations.

A field study was conducted during 2016–17 to evaluate the effectiveness of some biopesticides against Odontotermes obesus (Rambur) in tea ecosystem. The study revealed that the plants treated with Metarhizium anisopliae (Metchnikoff and Sorokin) showed the least number and infestation (stem) (13.86% and 12.04% and 14.11% and 12.04%) which was significantly superior over other treatments but statistically at par with Heterorhabditis indica (Poinar, Karunakar and David) treated plant (14.49% and 13.73% and 15.60% and 14.26%) after 30 and 60 days of treatment. The plants treated with AAU jatropha oil 50 EC exhibited infestation of 15.52% and 16.56% on number basis and 14.60% and 15.36% on portion basis, while neem oil treated plant recorded 16.01% and 17.09% of number and 15.17% and 16.44% of portion of infestation after 30 and 60 days of treatment, respectively. The untreated control plots recorded 38.44% and 37.35% and 40.32% and 39.48% of infestation on number and portion (stem) basis after 30 and 60 days of treatment, respectively.

Results indicated that microbial treatments were significantly superior in reducing plant mortality as well as grub population over the untreated control. However, among all the microbial tested, combined formulation of Heterorhabditis indica and Meterhizium anisopilae treated plots recorded significantly lower per cent of plant mortality (14.16 & 16.00% after 40 and 60 days of sowing, respectively) and lowest number of grubs per sq. m. (3.88) resulting in highest grain yield of 5.81 q/ha. Yield recorded in case of M. anisopliae, NBAII 04, Beauveria bassiana with H. indica and B. bassiana alone, NBAII 01 and NBAII 06 recorded a grain yield of 5.35, 4.77, 4.28, 4.29, 4.04 and 4.71 q/ha, respectively. The untreated control plots registered a very high level of plant mortality both at 40 and 60 days after sowing (29.95 & 32.06% respectively) having maximum population of grubs (7 numbers/sq.m.) with a grain yield of 4.03 q/ha.

Field studies were conducted to evaluate the efficacy of six insecticides against white grub, Lepidiota mansueta, in potato in 2012 and 2013 at Majuli river island in Assam (India). All the insecticide treatments significantly reduced tuber damage as against untreated control. Of the insecticides tested, fipronil 5 SC @ 150 g a.i.ha−1 showed low tuber damage on weight basis (5.24 and 4.57%) and was at par with fipronil 5 SC @ 100 g a.i.ha−1 (5.91 and 5.09%), chlorpyriphos 20 EC @ 400 g a.i. ha−1 (5.55 and 6.2%) and quinalphos 25 EC @ 400 g a.i.ha−1 (6.14 and 6.72%). On number basis, fipronil 5 SC @ 150 g a.i.ha−1 showed lowest tuber damage (4.2%), followed by chlorpyriphos 20 EC @ 400 g a.i.ha−1 (5.25%) and quinalphos 25 EC @ 400 g a.i.ha−1 (5.66%). All insecticide treatments were at par in tuber yield, except emamectin benzoate 5% SG @ 12.5 g a.i.ha−1. Highest cost benefit ratio was observed in chlorpyriphos 20 EC @ 400 g a.i.ha−1 treatment (2.50 and 2.62), followed by quinalphos 25 EC @ 400 g a.i.ha−1 (2.23 and 1.85). Chlorpyriphos 20 EC @ 400 g a.i.ha−1 and quinalphos 25 EC @ 400 g a.i.ha−1 seem better alternatives than fipronil to reduce infestation of L. mansueta in potato.

An investigation was carried out during 2010–11 and 2011–12 using five microbes and an insecticidal check against termite in preserved setts of sugarcane (Saccharum officinarum L.) in Assam. Among the microbials, the setts treated with Metarhizium anisopliae @ 1012 spore litre−1 recorded lowest infestation of termite (21.25 and 19.06% and 22.62 and 23.59% as numbers and portions of setts attacked) with germination percentage of 67.86 and 67.81 during 2010–11 and 2011–12, respectively. The insecticidal check i.e. chlorpyriphos 20 EC @ 2 ml litre−1 recorded least mean number (15.16 and 14.84%) and portion of setts (14.81 and 16.10%) infestation by termite coupled with a marked increase in per cent germination (78.02 and 76.82%). Experimental results further indicated very high level of infestation of termite in untreated control, which led to the poor germination of setts.