Pink bollworm, Pectinophora gossypiella (Saunders) infestation on Bt cotton is a major concern to cotton production in India. The genetic diversity and phylogeographic structure of the insect in ...light of PBW resistance needs to be revisited. The objective of this study was to identify different haplotypes of pink bollworm and their distribution in India. To achieve this we studied the population structure in 44 cotton growing districts of India. The partial mitochondrial COI sequence analyses of 214 pink bollworm populations collected from 44 geographical locations representing 9 cotton growing states of India were analysed. Genetic diversity analysis exhibited presence of 27 haplotypes, among them Pg_H1 and Pg_H2 were the most common and were present in 143 and 32 populations, respectively. Distributions of pairwise differences obtained with partial COI gene data from the overall Indian populations are unimodal, suggesting population expansion in India. Significant neutrality test on the basis of Tajima' D and Fu's Fs presented a star-shaped haplotype network together with multiple haplotypes. The unimodal mismatch distribution, rejection of neutrality test with significant negative values supported the theory of demographic expansion in cotton pink bollworm populations in India. Genetic data not only provides us with a perspective of population genetics, but also that the two populations of pink bollworm, those occurring early in the season are genetically close to the late season populations with respect to their partial CO1 region. Resistance to Cry toxins does not seem to have had an impact on this region of the mt DNA in populations of pink bollworm.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
There is a global concern about the effects of climate change driven shifts in species phenology on crop pests. Using geographically and temporally extensive data set of moth trap catches and ...temperatures across the cotton growing states of India, we predicted the phenology of cotton pink bollworm Pectinophora gossypiella (Saunders). Our approach was centered on growing degree days (GDD), a measure of thermal accumulation that provides a mechanistic link between climate change and species' phenology. The phenology change was predicted by calculating absolute error associated with DD and ordinal date, an alternative predictor of phenology, for peak moth abundance. Our results show that GDD outperformed the ordinal dates in predicting peak moth abundance in 6 out of 10 selected locations. Using established thresholds of 13.0/34.0 °C, mean DD accumulated between the consecutive moth peaks across different years were estimated at 504.05 ± 4.84. Seven generations were determined for pink bollworm in a cropping season, the length of which varied between 35 and 73 days in response to temperature. Pink bollworm population reached its peak during third generation which can be the target for management actions. The study provides essential information for developing pink bollworm management strategies under climate change.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A survey was conducted in 47 locations in nine cotton-growing states of India to identify the composition of mealybug species occurring on cotton. Results of the taxonomic study showed that two ...mealybug species, the solenopsis mealybug, Phenacoccus solenopsis (Tinsley), and the pink hibiscus mealybug, Maconellicoccus hirsutus (Green), were found to infest cotton plants from all nine cotton growing states of the country. However, P. solenopsis was found to be the predominant mealybug species, comprising 95% of the samples examined. P. solenopsis, which was hitherto not reported to occur in India, now appears to be widespread on cotton in almost all cotton-growing states of the country. P. solenopsis is an exotic species originated from the USA and was reported to damage cotton and crops of 14 families. This report discusses the implications of the introduction of this exotic polyphagous pest species and the necessary steps to mitigate its potential threat to agriculture in India.
Background
Insecticidal proteins from the
Bacillus thuringiensis
(
Bt
) marks the genetically modified cotton crop that was commercialized in India in March 2002 for the control of lepidopteron ...bollworms. Despite organized initial control, the pink bollworm (PBW),
Pectinophora gossypiella
(Saunders), adapted itself to cry toxins resulted in field control failures in 2016 and 2017. The present study was designed to understand the survival and development of PBW populations differing in susceptibility to Cry toxins on Bt and non-Bt plants.
Results
For assessment of infestation, populations were collected from different cotton growing states. Per cent infestation of flowers and green bolls in the study areas were in the range of 3.09–29.26 and 36–91.20% for flowers and green bolls, respectively. Among different locations highest magnitude of resistance to Cry1Ac (371.8-fold) and Cry2Ab (4214.3-fold) was spotted in late season populations of Rajkot collected from bolls. Further, in order to confirm field level resistance of surviving larvae on high and low concentrations of Cry toxins, larvae were pooled and subjected to boll bioassays. Results revealed that, none of the larvae from susceptible populations survived on BGII bolls. Although, the same populations showed a survival of 38 and 32%, which led to 80% locule damage on non-
Bt
cotton. Maximum survival (32%) and locule damage (70%) was observed for Maharashtra (F-H) Cry2Ab and Gujarat (B-H) Cry2Ab populations recorded 36% survival and 70% mortality, respectively, on BGII cotton and 58.33% survival and 60% locule damage on non-
Bt
cotton, respectively. Populations derived from survivals on low concentrations produced the lowest survival and locule damage on
Bt
cotton. Maximum number of mines on epicarp (2.4 mines/boll) was recorded by susceptible population on NBt cotton. Green bolls of
Bt
and NBt cotton did not differ in the number of mines.
Conclusion
It was concluded that none of the larvae from susceptible populations survived on BGII bolls. Although, the same populations showed a survival of 38 and 32%, which led to 80% locule damage on non-
Bt
cotton
The pink bollworm
Pectinophora gossypiella
(Saundars) (Lepidoptera: Gelechidae) has recently emerged as a serious menace on Bt cotton in India. Extensive roving surveys were conducted in 83 locations ...spread across 16 major cotton growing districts of Maharashtra State, India to assess the level of pink bollworm infestation in Bt cotton. The dynamics and severity of pink bollworm damage during the different stages of boll development (90–130 days of crop age) were assessed based on random sampling of green bolls, opened bolls and picked bolls per plant and number of locules damaged per boll. Survey results revealed a widespread infestation of pink bollworm on Bt cotton across the surveyed sites in a range of 40–95% which accounts for anticipated yield losses between 20 and 30%. A typical pattern of progressive increase in the level of pink bollworm infestation and intensification of locular damage with the advancement of the crop season was observed. The pink bollworm hitherto was supposed to be under control since the introduction of Bt cotton in India, now it appears to be widespread, especially on Bt cotton throughout the cotton growing areas of Maharashtra State which shares approximately 36% and 25% of the country’s cotton area and production, respectively. This article discusses the implications of serious outbreak of pink bollworm infestations in Bt cotton and also suggest measures necessary to mitigate its potential threat to Indian cotton production. The modulation of management practices aimed at manipulation of cotton cropping pattern being followed in the country in general and Maharashtra in particular could strengthen the management of pink bollworm populations effectively. We discuss the practicality of several management options aimed at achieving this goal.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
The cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), is an invasive pest of cotton, apart from several other important crops, and poses a serious threat to ...agricultural economy all over the world. Studies on the biology and population growth parameters of P. solenopsis on the five most preferred host plants, namely cotton (Gossypium hirsutum L.) (Malvaceae), China rose (Hibiscus rosa-sinensis L.) (Malvaceae), tomato (Lycopersicon esculentum Mill.) (Solanaceae), congress grass (Parthenium hysterophorus L.) (Asteraceae) and okra (Abelmoschus esculentus (L.) Moench) (Malvaceae) were undertaken in the laboratory under controlled temperature and relative humidity. The mean cumulative development time of females was 16.61 days on cotton, 14.16 days on China rose, 14.13 days on okra, 14.00 days on tomato and 13.57 days on congress grass. The longest oviposition period was recorded on cotton (15.20 ± 1.87 days), while it was in the range of 9-10 days in the remaining host plants. Females lived longer (27.40 ± 1.76 days) when reared on cotton, while their life was shortest on tomato (14.60 ± 0.96 days). The highest fecundity was observed on cotton (328.30 ± 23.42), whereas it was found to be in the range 178-212 on the other hosts. The survival frequency from crawler to adult in females was highest on cotton (27.53%), while it was the lowest on tomato (15.87%). The highest net reproductive rate (284.3 females/female/generation), mean length of a generation (31.24 days), and intrinsic rate of increase (0.19 day−1) were recorded on cotton. The finite rate of increase was in the range of 1.18-1.20 (females/female/day) for all the selected host plants. The weekly multiplication rate was highest on China rose and congress grass (3.78), while it was the least on tomato (3.28). The corrected generation time was dissimilar in all the selected host plants, being highest on cotton (31.39 days) and the least on congress grass (27.71 days). The doubling time was shortest on congress grass (3.61 days), while it was longest on tomato (4.11 days). Hence, the host plant species significantly affects population growth of P. solenopsis.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The cotton aphid, Aphis gossypii, is a major sap sucking insect of cultivated cotton, Gossypium sp. We investigated the effects of temperature on the biological parameters of A. gossypii by fitting ...different non-linear models to the data obtained from constant temperature experiments carried out between 12 and 32 °C. The pest risk in different geographical areas was simulated using GIS tools and represented by two spatial indices viz. establishment risk index (ERI) and generation index (GI). The results revealed that the development rate as a function of temperature increased linearly until approximately 27 °C, after which it became non-linear. Mean longevity of adult female was highest at 12 °C (10.10 ± 0.33 days) and shortest at 32 °C (3.70 ± 0.14 days). The lower and upper development threshold temperatures predicted for immature development of A. gossypii were 6.24 °C and 34 °C, respectively. The temperatures between 22 and 27 °C were found as favourable range for A. gossypii development, survival and reproduction. Majority of the Indian cotton areas were predicted optimally suitable for establishment and survival of A. gossypii (ERI > 0.6 and GI > 30.0). The risk mapping based aphid management strategy is suggested in the conclusion section of this article.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Abstract
Background
The cryptic nature of pink bollworm
Pectinophora gossypiella
(Saunders) larvae enables its reduced vulnerability to insecticidal control. Further, the development of resistance ...against
Bacillus thuringiensis
(Bt) toxins posed a serious threat to transgenic cotton cultivation. This necessitated determining the critical timing of spray applications on the control effectiveness. This study assessed the influence of egg age (freshly laid
vs
. three-day-old) and the location of larvae (directly exposed to the insecticide residues on the boll rind
vs
. burrowed inside the bolls) on insecticide control efficacy.
Results
The results revealed a significant decrease in the ovicidal activity of tested insecticides with an increase in the age of eggs from one day old to three days old (paired
t
-test,
P
< 0.05). The larvae directly exposed to the insecticide residues on the boll rind were more susceptible (> 80% mortality) than the larvae exposed after they had burrowed inside the bolls (< 49% mortality). The inhibitory effects of tested insecticides on developmental biology were more pronounced in the experiment on pre-larval release insecticide treatment compared with insecticide treatment given post-larval release and entry inside the bolls.
Conclusion
Egg age influences the insecticide susceptibility, as does the larval location, directly exposed vs burrowed inside the bolls. Older eggs and the larvae that had burrowed inside the green bolls of cotton were relatively less susceptible to the insecticide treatments. The toxic effects of insecticides on egg and larval stages were primarily ephemeral. These findings are significant for devising a comprehensive strategy for pink bollworm management on a sustainable basis.
The present work is focused on the comparative analysis of electrochemical and structural properties of anode materials for solid oxide fuel cells (SOFCs) and the influence of factors affected on ...electrode performance. The Cu0.5Ce0.5O2−δ was prepared by Citrate–Nitrate route (CNP) and its formation is confirmed by XRD. The crystallite size of anode materials decreases with change of synthesis route. The highest conductivity is found to be 3.7 × 10−2 and 5.2 × 10−2 S cm−2 at 660 °C before and after reduction for CNP with suitable mechanical strength. The electrochemical performance of anode/electrolyte/anode interface of Cu0.5Ce0.5O2−δ is studied after reduction in presence of gas mixture (10%H2 + 90%N2) using electrochemical impedance spectroscopy. The conductivity for the Cell-800 prepared by CNP in presence of gas (10%H2 + 90%N2) shows lowest activation energy 1.28 eV. Thus, CNP is most promising method for obtaining the suitable anode material for the application of SOFC than Urea–Nitrate Process (UNP) and Glycine–Nitrate Process (GNP).
► Focus to improve the electrochemical performance of CuxCe1−xO2−δ anode materials. ► Electronically and mechanically CNP is more suitable for CuxCe1−xO2−δ preparation. ► Four-probe method is used to measure the D.C. conductivity of all samples. ► D.C. conductivities are improved after reduction of CuxCe1−xO2−δ in 10%H2 + 90%N2. ► The ASR of Cell-800 prepared by CNP found to be 116.36 Ω cm2 which is lowest.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
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