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Biopesticides from botanicals for organic cultivation
 
Introduction
 
Unbalanced and extensive use of broad-spectrum pesticides has created more problems than resolving them. The development of pesticide resistance, vast destruction of beneficial organisms, rapid resurgence of target pest population, uncontrolled outbreak of secondary pests and undesirable environmental effects causing socio-economic problems has arisen. In addition, the advent of Maximum Pesticides Residue Limit for horticultural products for export, have promoted an intensive search for natural pesticides. Steadily growing problems of the pest resistance to synthetic pesticide, pollution of the environment and the side effects on the beneficial flora and fauna demands an intensive search for new safer pesticide. Therefore, today there is a need to develop method that is capable of reducing the large-scale utilization of synthetic pesticides for crop protection. Among the methods used in Integrated Pest Management, plants and their by products have played a significant role.
 
 
Background
 
Biopesticides and Entomology was always considered as a useful support area at the institute but there was a lack of qualified persons available. Dr. P. Pushpangadan created this group in 2001 to cater to the demand of safe and eco-friendly insecticides which is increasing in view of organic cultivation. Botanicals are considered as one of the available alternative to chemical pesticides, and more than 2000 species of plants are known to contain insecticidal active principals.

Biopesticides and entomology laboratory has been created in biomass biology division of the institute with an aim of developing commercially viable biopesticides in particular botanical pesticides for control of various crop pests as well as household pests.
 
 
R&D Program and major achievements
 
The Group is working on several potential insecticidal plants for the purpose of development of commercially viable biopesticides. Several crude and semi purified plant extracts have been screened against storage insect pests such as Trogoderma granarium, Tribolium castaneum and Sitophilus oryzae and polyphagous crop pests such as Spodoptera litura and Spider mites Tetranychus sp. The effective compounds are being formulated as pesticides. The group is also establishing facilities for rearing of mosquitoes and testing of mosquitocidal/ mosquito repellent compounds.
 
Bio-Control of Storage pests and Spodoptera litura
 

Azadirachtin (C35H44O16), Salanin (C35H44O9) and Nimbin (C30H30O9) were isolated from seed, oil and leaves of neem. Formulations having enriched fractions of neem have been developed. Among all the tested formulations, aza based formulation showed the best results against storage pests and Spodoptera litura.

Enriched neem oil in synergistic formulation with essential oil of Acorus calamus was examined for activity against three storage pests, Trogoderma granarium, Tribolium castaneum and Sitophilus oryzae. Antifeedant, growth reduction and mortality were also checked against Spodoptera litura. Topical application was employed for contact toxicity studies and filter paper impregnation was used for testing fumigant and repellent effect. The adult of S. oryzae was found to be more susuptible than T. granarium and T. castaneum to contact toxicity of the essential oil at LD50 level, with the value of 1.2 µg/insect, 5.4 µg/insect and 25.3 µg/insect, respectively. For fumigant toxicity, S. oryzae was more susuptible than T. granarium and T. castaneum at LD50 with the value of 7.38 mg/L air, 20.22mg/L air and 23.66mg/L air, respectively. In case of repellency essential oil was more effective against the adult T.castaneum (EC50= 0.013mg/cm2) than T. granarium (EC50= 0.921 mg/cm2).

Neem oil extract and essential oil showed synergistic action when applied in combination. Several fold increase in toxicity and repellency was found against storage pests.

Essential oil exhibited excellent growth reduction activity against Spodoptera litura at very low concentrations. The formulation is being further improved for effectivity, shelf life and method of application.

Apart from the crude and purified extracts of neem, Pongamia and several other plants, our group is also concentrating on the activity of essential oil of several plant that may be useful in controlling several insect species, specially stored product pests due to their characteristic smell. We have tested several essential oil such as, Acorus calamus, Callistomon sp., Cymbopogon caesius and Vitex negundo. Field experiments are carrying out to come up with an effective product.
 

Bio-Control of Spodoptera litura
 
Methanolic extract of Pongamia oil showed maximum antifeedant (EC50=0.21) and growth reduction activity (EC50=0.11%), this is due to presence of high concentration of karanjin and pongamol. Methanolic extract of Pongamia bark showed good antifeedant (EC50= 2.6%) and growth regulatory (EC50= 1.5%) activity against S. litura.

Methanolic extract of Pongamia leaf, crude oil and non-polar fraction of oil did not show any significant activity.

An effective oil based formulation having azadirachtin-enriched fraction of neem oil and karanjin enriched fraction of Pongamia oil is developed for the control of polyphagous crop pest S. litura.
 
Bio-Control of Spider mites (Tetranychus urticae)
 
Spider mites are major problem in betelvine cultivation around Lucknow of Uttar Pradesh. Seed oils of Pongamia, Neem and Mahua were evaluated in the lab for toxicity against Spider mites collected from betel vine conservatories. All the oils tested were found effective in controlling pest at very low doses. The Pongamia oil was most toxic (LC50: 0.13 %) followed by Neem (0.17%) and Mahua (0.42%). Combination of (1:1) Neem and Pongamia was less toxic (LC50 0.25) than individual oils alone. Neem Pongamia and mahua oils caused significant mortality of eggs at 4%.

Residual toxicity of selected pesticides, against two spotted spider mites1 infesting French bean, was checked. The LT50 was as follows : monotroph 0.04% and ethion 0.1% (19 days) >dicofol 0.05% (14 days) > acephate 0.06% and bifenthrin 0.05% (10 days) > fluvilinate 0.0125% and 0.025% (5-7 days) > endosulfan 0.07% and wettable sulphur 0.2% (>2 days).

The overall results on residual toxicity revealed that monocrotophos, ethion and dicofol were effective against T. urticae upto 18 –20 days on french bean whereas endosulfan and wettable sulphur were least effective.
 
 
Literature cited
 
  1. ChandraShekar, K. and Srinivasa, N. (2003). Residual toxicity of selected pesticides, against two spotted spider mites Tetranychus urticae Koch (Acari: Tetranychidae) infesting French bean, J. Ent. Res. 27(3): 197 - 201.
 
 
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