Comparative Toxicity of Nitenpyrem and Neem Oil Against Amrasca biguttula biguttula in Okra

The Jassid, Amarasca bigutulla bigutullaa is an important sucking pest of the okra crop. An experimental study was conducted during 2018 to check the comparative toxicity of nitenpyrem and neem oil against jassid under okra field conditions. The study revealed that 24 hours after treatment, nitenpyrem was found more toxic and effective with maximum reduction of jassid population (72.15%). Whereas, 120 hours after treatment with 4% neem oil, 15.05% jassid reduction was observed. The mortality rate of the jassid was increased with increasing in time after application of chemical insecticides. The study concluded that insecticide was most toxic and gives higher mortality of jassid as compared to neem oil. Keywords: Abelmoschus esculentus, Malvaceae, Amarasca bigutulla bigutullaa, botanicals, insecticides, Pakistan

EFFICACY OF CHITIN SYNTHESIS INHIBITORS IN ARRESTING GROWTH AND DEVELOPMENT OF OKRA JASSID, AMRASCA BIGUTTULA BIGUTTULA (ISHIDA)

Chitin synthesis inhibitors (CSIs) are potential inhibitory chemical compound that disrupt molting process by interfering chitin synthesis and kill insects before attaining maturity. In this study, some chitin synthesis inhibitors (CSIs) viz. Tacoma 40SC (Buprofezin), Heron 5EC (Lufenuron), Pyrifen 10.8EC (Pyriproxifen) and Chitosan 75WP were tested against okra jassid, Amrasca biguttula biguttula (Ishida) to elucidate their potential effects in arresting body growth and development. The nymphs of jassids were exposed to selected CSIs through different application methods like topical, leaf-dip and the combination of both topical and leaf-dip. Weight data was collected at 7 days after treatment (DAT) application. Results showed that all of the CSIs except Chitosan had significant effect on the body weight reduction of okra jassid. Growth reduction was clearly concentrations and application method dependent. It has shown that higher concentrations were found to be more effective than lower concentrations. Bioassay study has showed that all the selected CSIs became able to enter in the insect body through contact as well as stomach action to disrupt molting process by inhibiting chitin synthesis that confirmed the contact and systemic actions of the selected CSIs. This study recommends that Tacoma 40SC @ 1.0 ml/L, Heron 5EC @ 1.5 ml/L and Pyrifen 10.8 EC @ 1.5 ml/L may be the potential alternatives of conventional neurotoxic insecticides in controlling jassids as they reduced 50-60% weight compared to untreated control. Moreover, protocols developed in this study for jassids collection and their safe transferring inside the petri dishes would be a useful and convenient approach for the researchers.

Transcriptome analysis unravels RNAi pathways genes and putative expansion of CYP450 gene family in cotton leafhopper Amrasca biguttula biguttula(Ishida)

Amrasca biguttula biguttula is an important pest of cotton and okra in the Indian subcontinent. Presently limited genomic/ transcriptomic information is available for this insect in any open source databases. To initiate molecular studies in this insect, we report first assembled and annotated de novo transcriptome of cotton leafhopper. Out of 75,551 transcripts, 39613 CDS (Coding Sequence) were predicted with 35282 showing positive blast hits with NCBI nr database . From the Gene ontology (GO) analysis, 7431 CDS were annotated. KEGG pathway analysis categorized CDS into 22 different functional categories. The majority of CDS were annotated in signal transduction and transport catabolism pathways. The sequence data was screened for RNAi pathway genes and presence of 37 transcripts associated with this process confirmed the existence of robust RNAi machinery in this insect. The role of core RNAi machinery genes ( Dicer-2 , Ago-2 , Piwi and Staufen ) has been validated through dsRNA feeding studies. The data resource has also been used to identify potential RNAi targets and genes associated with insecticide detoxification specifically CYP 450 family.

Effect of Sowing Dates and Nitrogen Levels on Popula-tion of Okra Jassids (Amrasca biguttula biguttula Ishida)

Okra (Abelmoschus esculentus L. (Moench) is one of the most important vegetable crops grown in Nepal. The crop is susceptible to various insect pests of which jassids (Amrasca biguttula biguttula Ishida.) is most predominant which reduces production and deteriorates seed quality of okra. A field study was conducted at Horticulture Farm, Agriculture and Forestry University, Rampur, Chitwan, Nepal to elucidate the effect of sowing date and nitrogen levels on the population and damage of jassids from April to September 2018. Three levels of nitrogen (100, 200 and 300 kg N ha-1) and five sowing dates (8th April, 20th April, 2nd May, 14th May and 26th May, 2018) were evaluated in randomized complete block design with three replications. Results indicated that the highest damage score was recorded in okra which was sown on 8th April (2.39) followed by 20th April (2.31) and 2nd May (1.26). The highest damage score of jassids was obtained with the use of nitrogen at the rate of 200 kg ha-1 (1.94) followed by 300 kg/ha (1.72) and 100 kg ha-1 (1.54). Mean population of jassids was maximum with okra sown on 20th April (29.91) and minimum with okra sown on 26th May (6.95). This study showed that late planting i.e. 26th May and applying low level of nitrogen i.e. 100 kg N ha- 1is an effective approach for reducing the jassids population and its damage in okra.