Isolation, Semi-Synthesis and Antifeedant Activity of Constituents from Derris scandens Benth.

This work describes the semi-synthesis of derivatives from derris isoflavone-A (1), scandenin (2) and 6,8-diprenyl-4′,5,7-trihydroxy isoflavone (3) which are major constituents isolated from chloroform extract of Derris scandens Benth. All the semi-synthesized derivatives (4-11) were characterized by NMR and mass spectroscopic techniques. All these derivatives are evaluated for their antifeedant activity in castor semilooper and tobacco caterpillar using a no-choice laboratory bioassay. The results demonstrated that scandenin (2), compounds 5, 7 and 10 have shown potent insecticidal activity.

Midgut aminopeptidase N expression profile in Castor semilooper during sublethal Cry toxin exposure

Midgut of lepidopteran larvae is a multifunctional tissue, which performs roles in digestion, absorption, immunity; transmission of pathogens and interaction with ingested various molecules. The proteins localized at the inner apical brush border membrane are primarily digestive proteases but some of them like aminopeptidase N, alkaline phosphatase, cadherins, ABC transporter C2 etc. interact with Crystal (Cry) toxins produced by Bacillus thuringiensis (Bt). In the present study aminopeptidase N (APN) was characterized as Cry toxin interacting protein in larval midgut of castor semilooper, Achaea janata. Transcriptomic and proteomic analyses revealed the presence of multiple isoforms of APNs (APN1, 2, 4, 6 and 9) which have less than 40% sequence similarity but show the presence of characteristic “GAMENEG” and zinc-binding motifs. Feeding of sublethal dose of Cry toxin caused differential expression of various APN isoform. Further, 6th generation Cry toxin exposed larvae showed reduced expression of APN2. This report suggests that A. janata larvae exploit altered expression of APNs to overcome the deleterious effects of Cry toxicity, which might facilitate toxin tolerance in long run.

Ovicidal and toxic effects of certain plant extracts to the castor semilooper, Achaea janata L. (Noctuidae: Lepidoptera)

Ovicidal and toxic effects of crude leaf extracts of Clerodendrum inerme, Clerodendrum splendens, Clerodendrum multiflorum, Vitex negundo and Argemone mexicana were evaluated against the castor semilooper, Achaea janata L. (Noctuidae: Lepidoptera) using different bioassay methods. Among the extracts tested, the highest ovicidal activity was observed in C. splendens as well as A. mexicana with LD50 values of 7.65 and 9.14 mg-1, respectively. Leaf extracts of A. mexicana and C. inerme were toxic to both third and fourth instar larvae of A. janata through topical application. However, the extracts of A. mexicana and C. inerme found to be more toxic to third instar larvae with 70 and 73 per cent mortality, respectively. The lowest LD50 value of 5.33 mg-1 was recorded by A. mexicana extract and was followed by C. inerme extract with LD50 value of 7.26 mg-1. Present results indicated that A. mexicana and C. inerme plants have potential to use in IPM programme.

Seasonal abundance and bio-efficacy of different insecticides against castor semilooper on castor

The present study was conducted at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Regional Research Station, Bawal, Haryana (India). The larvae of castor semilooper remain active from 30th standard weeks to 47th standard weeks. The maximum larval population was recorded on the 32th standard week (6.1 larvae per plant) and 38th standard meteorological weeks (6.2 larvae per plant) due the high rainfall, 158 and 120 mm, during these weeks, respectively. Correlation indicates that minimum temperature, evening relative humidity and rainfall exhibited a positive relationship (r- 0.588, 0.577 and 0.650) with the larval population. Bio-efficacy of four insecticides with different doses was tested against A. janata infesting castor crop. One day after spraying thiodicarb @ 468 g proved best toxicant followed by thiodicarb @ 375 g, deltamethrin @ 11.2 g, deltamethrin @ 10.5 g, quinalphos @ 250 g, quinalphos @ 200 g, novaluron @ 100 g and novaluron @ 75 g. At three days after spraying, it was found that novaluron @ 100 g was the most effective followed by novaluron @ 75 g, thiodicarb @ 468 g, deltamethrin @ 11.2 g, thiodicarb @ 375 g, deltamethrin @ 10.5 g, quinalphos @ 250 g and quinalphos @ 200 g. At seven days after spraying novaluron @ 100 g proved to be best toxicant followed by novaluron @ 75 g, thiodicarb @ 468 g, thiodicarb @ 375 g, deltamethrin @ 11.2 g, deltamethrin @ 10.5 g, quinalphos @ 250 g and quinalphos @ 200 g. Novaluron 100 g was the overall most effective with 75.97 mean per cent reduction in larval population.