Ecological engineering in low land rice for brown plant hopper, Nilaparvata lugens (Stål) management.

Rice field bunds and edges can act as near crop habitats, available for planting flowering plants to attract and conserve the natural enemies. We evaluated the effect of ecological engineering on the incidence of Brown Planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera; Delphacidae) and the abundance of its predators in the rice variety Pusa Basmati-1121. Plots included the oilseed crops viz. sesamum, sunflower and soybean, with plantings of flowering crops marigold, balsam and gaillardia as bund flora around the edges of rice plots. Ecologically engineered plots contained both crops+flowers and resulted in a significantly reduced BPH population per hill in rice plots for 2019 (6.3) and 2020 (9.4) compared to the control plots (9.8 and 14.4). Ecologically engineered plots also witnessed the delayed appearance of BPH during each growing season. Peak BPH populations are lower in the ecologically engineered plots than in the control grounds. Furthermore, the activity of natural enemies, viz., spiders, mirid bugs and rove beetles was the highest in rice fields planted with oilseed crops like sesamum, sunflower and soybean. Olfactory response studies showed that the attraction response of spiders toward sesamum and balsam leaves was more significant than in other crop plants. Rice yield was enhanced in plots planted with crops+flowers during both seasons compared to control plots. Planting of oilseed crops plants such as sesamum, sunflower and soybean with flowering crops such as marigold, balsam and gaillardia as bund flora on the bunds around the main rice field enhanced the natural enemy activity, suppressed the planthopper population, and increased yields. Based on the results, we recommend including ecological engineering techniques as one of the management components in the Integrated Pest Management programme for rice crops.

Bioefficacy of engineered Beauveria bassiana with scorpion neurotoxin, LqqIT1 against cotton mealybug, Phenacoccus solenopsis and cowpea aphid, Aphis craccivora.

Cotton mealybug, Phenacoccus solenopsis (Tinsley) and cowpea aphid Aphis craccivora (Koch) are notorious polyphagous, hemipteran sap sucking insect pests. A recombinant toxin gene 'LqqIT1' from the scorpion Leiurus quinquestriatus quinquestriatus (Ehrenberg) was cloned in the pAL1 fungal expression vector and then expressed in the entomopathogenic fungus Beauveria bassiana (Balasmo) using genetic modification techniques. The genetically transformed B. bassiana strain (BbLqqIT1-3) and its un-transformed parent strain (Bb-C) were screened to infect the third instar nymphs of P. solenopsis and first instar nymph of A. craccivora through leaf treatment and topical application (spray) method at 1 * 107 spores per ml concentration. The recombinant strain BbLqqIT1-3 was highly pathogenic against A. craccivora but non pathogenic to P. solenopsis. BbLqqIT1-3 induced 72 and 43.33% mortality in A. craccivora nymphs 96 h after leaf treatment and topical application, respectively. The nymphs of A. craccivora infected with BbLqqIT1-3 displayed classical neurotoxic symptoms such as sluggishness, solublize and liquification of the body. Crude soluble toxin protein, BbLqqIT1a-CSE and Bb-WT-CSE was extracted from the BbLqqIT1-3 and Bb-C, respectively using ammonium sulphate precipitation method, and their oral toxicity was analyzed at 5 µg/ml concentration. The survival of the studied insects was negatively affected by the crude soluble toxin extracts. The LT50 values of BbLqqIT1a-CSE against P. solenopsis and A. craccivora were 22.18 and 17.69 h, respectively. Exposure to crude soluble toxin extracts also accounted for the imbalance of ionic concentrations in the hemolymph of treated insects such as hyperpotassemia (3.53-8.18 meq/ml) in the P. solenopsis and hypopotassemia (7.52-0.47 meq/ml) in A. craccivora. The transformed fungus BbLqqIT1-3 strain exhibited promising results in invitro study.

Wheat as a new host for potato aphid Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae) and construction of its age-stage two-sex life tables.

Wheat (Triticum aestivum L.) is the major global staple food crop that meets the food security demands of various nations across the continents. The recent reduction in wheat production is attributed to several biotic and abiotic factors especially, temperature and rainfall patterns, and pest occurrence. Among insect pests, aphid species are emerging as new pests of economic importance in India and elsewhere. The present investigation identified a new association of Macrosiphum euphorbiae Thomas with the wheat crop. Life table parameters were studied for M. euphorbiae and Rhopalosiphum padi fed on wheat foliage. The total nymphal duration and life cycle duration, respectively, of R. padi (4.76 ± 0.54 and 9.71 ± 1.38 days) and M. euphorbiae (5.84 ± 0.69 and 9.96 ± 1.31 days) were significantly different for these species. The fecundity of the two aphid species was 23.95 ± 8.67 and 11.6 ± 4.10 progeny/female, respectively. Age-specific survival rate (lx), age-specific fecundity (fx), and population age-specific fecundity (mx) were higher in R. Padi compared to M. euphorbiae. Reproductive value (Vxj) was high in R. padi and the duration of reproduction was less, while these parameters showed an opposite trend in M. euphorbiae. The gross reproduction rate (GRR) was found higher in R. Padi (29.17 offspring/adult lifetime) compared to M. euphorbiae (19.58 offspring/adult lifetime). The M. euphorbiae being a pest of solanaceous crops seems to have shifted to a new host, i.e., wheat. This new adaptation strategy to survive for long periods on a wheat crop might pose a serious threat to wheat crop cultivation in near future.

Efficacy of genetically transformed Metarhizium anisopliae against Spodoptera litura and Aphis craccivora.

To increase the insecticidal potency of the entomopathogen, Metarhizium anisopliae (Metsch.) Sorok, the fungus was genetically modified with scorpion neuro ß-toxin LqqIT1a and two different insect specific heterologous toxic proteins viz., Cry1a and GNA. LqqIT1 is an anti-insect neurotoxin derived from yellow scorpion, Leiurus quinquestriatus quinquestriatus (Ehren.). The present study reports the bio-efficacy of genetically modified fungus, M. anisopliae, in which scorpion neurotoxin gene 'LqqIT1' is stacked in its genome, for improved efficacy against the tobacco caterpillar, Spodoptera litura (Fab.) and Aphis craccivora (Koch). All the transformed clones of M. anisopliae were found potent against S. litura and A. craccivora under laboratory conditions. The virulent clones viz., Ma-2(2), Ma-2(7) and MaGKS-14 caused 40 to 90 per cent mortality at fourth day of treatment. Compared to untransformed parent strain, Ma-C, the median lethal time of transformed clones Ma-2(2), Ma-2(7) and MaGKS-14 got reduced by 2, 3 and 3-folds, respectively. No significant differences were noted with respect to percent mortality of transformed clone, MaGKS-13 in comparison to untransformed strain Ma-C. The results indicated that the incorporation of LqqIT1 toxin gene enhanced the potency of strain Ma-C, against immature stages of S. litura and A. craccivora by shortening the median lethal time without affecting conidial development. Therefore, LqqIT1 scorpion toxin gene showed the potential to improve efficacy of M. anisopliae against lepidopteran and hemipteran insects.

Foraging behaviour of Scymnus coccivora Ayyar against cotton mealybug Phenacoccus solenopsis Tinsley.

Predation is one of the significant biotic mortality factors reducing the insect pest population as functional response and the numerical response of the predator are the key factor regulating the population dynamics of predator prey species. This study is aimed to evaluate the functional response of all the developmental stages of Scymnus coccivora Ayyar (Coleoptera: Coccinellidae) against the different densities of cotton mealybug, Phenacoccus solenopsis (Tinsley) (Hemiptera: Pseudococcidae) and the numerical response of female predator. Experiments were carried out in controlled environment laboratory conditions at 25 ± 1 °C temperature, 60 ± 5% relative humidity and photoperiod of 16 h. Number of eggs consumed, number of eggs laid and the Efficiency of Conversion of Ingested food (ECI) were recorded daily. Results from the study revealed that all the developmental stages of S. coccivora exhibited a Type II response. Different parameters such as attack rate (a'), handling time (Th) and the maximum rate of predation were estimated using Roger's random attack equation and Holling Disc equation in which Rogers random attack equation was found best fit. Female has shown the highest attack rate (a') followed by IVth instar grub, male, IIIrd, IInd and Ist instar grub. With low handling time, IVth instar grub has shown maximum predation rate of 76.40 per day followed by female (75.86), male (58.79), IIIrd (22.84), IInd (19.65) and Ist instar grub (15.39). The numerical response increase was curvilinearly related to different prey densities with the highest number of eggs (11.8 ± 3.44) produced at highest prey density (160). The Efficiency of Conversion of Ingested food (ECI) was highest (64.49 ± 8.03) at prey density of 10. Understanding the factors that lead to variation in functional response of predator in natural population will advance our understanding of the effects of predation on individual and the effectiveness of coccinellid predators as biocontrol agent against cotton mealybug.

Genetic homogeneity in South American tomato pinworm, Tuta absoluta: a new invasive pest to oriental region.

South American tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae), is an important invasive pest of Tomato which invaded India and Nepal in 2014 and 2016, respectively. In the present study, samples from five localities of India and one from Nepal were used for the investigation of genetic diversity of T. absoluta by employing a fragment in the mtDNA gene-encoding cytochrome oxidase I (COI). Based on the partial COI gene, high genetic homogeneity was detected in T. absoluta populations of India and Nepal with rest of the world. Less nucleotide diversity (π 0.00137) was also detected in the populations of T. absoluta from different countries. This is first attempt to analyze molecular data for this new invasive species from India and Nepal.