Informatics Publishing Limited

Paramjit Kaur ¹, Vinod Kumar Dilawari ¹, Virash Kumar Gupta ¹, Satnam Singh ¹

Affiliations
1 Department of Entomology, Punjab Agricultural University, Ludhiana, Punjab, IN

Abstract

Transgenic cotton producing a Bacillus thuringiensis (Bt) Cry1Ac toxin is widely used for controlling the cotton bollworm, Helicoverpa armigera. The lessons learnt from the usage of insecticides suggest deployment of effective resistance management strategies to preserve the long-term utility of Bt-cotton. Consequently, it is important to understand the interaction of Cry1Ac toxin with distinct populations of the resistant alleles (homozygote resistant RR, susceptible SS and heterozygote RS or SR) keeping in mind the fitness cost associated with resistance. The present studies were under taken to understand the in vitro response of all such allelic populations. A critical analysis on the effects of Bt-toxin on different development stages shows that irrespective of the allelic genotype, the toxin exerts inhibitory influence on all the developmental stages. This effect is visualized as an enormous decrease in larval, pupal and adult weight, wing expanse of adults, adult life span and sex-ratio that was coupled with increase in time taken to pupate, pupal duration and total developmental period. Majority of the emerged adults possessed different types of abnormalities (wingless, deformed wings). They did not mate to lay eggs and if eggs were laid, they normally did not hatch, thus resulting in total loss of population(s). Cry1Ac toxin exerts a high cost of fitness on H. armigera and in this context susceptible and heterozygous genotypes were the most affected.

Keywords

American Bollworm, Bacillus thuringiensis, Bt Toxin, Fitness Cost, Resistance, Transgenic Cotton.

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Satnam Singh ¹, Maninder Shenhmar ¹, K. S. Brar ¹, S. K. Jalali ²

Affiliations
1 Department of Entomology, Punjab Agricultural University, Ludhiana - 141004, Punjab, IN
2 Project Directorate of Biological Control, Post Box No.2491, H. A. Farm Post, Hebbal, Bangalore - 560024, IN

Abstract

The efficacy of high temperature tolerant (PDBC strain) and Ludhiana (Punjab) strain of Trichogramma chilouis Ishii against early shoot borer Chilo infuscatellus Snellen was evaluated in farmers' field during 2004 and 2005. The PDBC strain was released from April to June @ 50000, 40000 and 30000 parasitoids/ha. and the Ludhiana strain @ 50000 parasitoids/ha. Nine releases of PDBC strain and Ludhiana strain @ 50000 parasitoids/ha were as effective as application of cartap hydrochloride (Padan 4G) @ 25 kg/ha in reducing the incidence of C. infuscatellus by 52.7 and 50.5% over untreated control, respectively. At lower two doses, the reduction was 29.03 and 34.7 per cent over untreated control and was significantly better as compared to untreated control and mechanical control (removal of dead hearts). The maximum parasitoid recovery (10.71% parasitization) was recorded with PDBC strain @ 50,000 parasitoids/ha and was on par with Ludhiana strain (9.88% parasitization) and significantly higher than that with lower doses of PDBC strain and control. Based on reduced pest incidence, higher parasitism and yield, the releases of T. chilonis (PDBC strain/Ludhiana) @ 50000 parasitoids/ha at 10 days interval from April to June can be successfully used for the suppression of early shoot borer.

Keywords

Chilo infuscatellus, Efficacy, Strains, Trichogramma chilonis.

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Satnam Singh ¹, M. Shenhmar ¹, K. S. Brar ¹, S. K. Jalali ²

Affiliations
1 Department of Entomology, Punjab Agricultural University, Ludhiana, 141 004, Punjab, IN
2 Project Directorate of Biological Control, Post Bag No. 2491, H. A. Farm Post, Hebbal, Bangalore, 560 024, Karnataka, IN

Abstract

The studies to evaluate the effect of insecticides recommended on sugarcane in Punjab, on parasitization and adult emergence of high temperature tolerant (PDBC, Bangalore) and Ludhiana (Punjab) strains of Trichogramma chilonis Ishii conducted during April-July 2004 at Entomological Research Farm and Biological Control Laboratory of Punjab Agricultural University, Ludhiana revealed that Ludhiana strain of T. chilonis was more tolerant to insecticides as compared to the high temperature tolerant strain. Among the insecticides, endosulfan (Thiodan 35EC) @ 395g a. i./ha was the safest followed by imidaeloprid (Conlidor 200 SL) @ 20g a, i./ha, triazophos (Hostathion 40EC) @ 600g a. i./ha, chlorpyriphos (Dursban 20EC) @ 175g a. i,/ha and malathion 50EC @ 1250g a. i./ha. The latter two at the applied doses were highly deleterious to the parasitoid.

Keywords

Insecticides, Parasitism, Strain, Sugarcane, Trichogramma chilonis.

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