Insect pest management in organic farming
Authors: Gugulotu Laxman
Division of Entomology, ICAR-Indian Agricultural Research Institute, New Delhi-110012
Corresponding author: laxmanagrico@gmail.com


Organic farming relies on methods which combine scientific knowledge of ecology and modern technology with traditional farming practices based on naturally occurring biological processes. It is a farming system that sustains the health of soils, ecosystems and people. The principal methods of organic farming include crop rotation, green manure and compost, mechanical cultivation and biological pest control. Farmers are faced with myriad of production challenges where the most common problems are pests, which include insects, diseases, and weeds. They integrate cultural, biological, mechanical, physical and chemical practices to manage pests.

Cultural practices: Rely on a strategy to make the crop or habitat unacceptable to pests by interfering with their oviposition preferences, host plant discrimination or location by both adults and immatures. Those can be achieved with practices such as crop isolation, mixed cropping, and crop rotation. The timing of sowing and planting can be used to allow young plants to establish to a tolerant stage before an attack occurs and to reduce the susceptible period of attack. Management of trap and nursery crops and surrounding environment is also included to divert insect attack away from the crop.

Mechanical: Include tillage, mowing, cutting, mulching and organic soil coverage and barriers. Tillage turning the soil between crops to incorporate crop residues and soil amendments. It also destroys weeds and disrupts pest life cycle.

Physical control : Mass-trapping of pests is an additional control measure. They often can easily be built with cheap material. Some examples include: 1) Light traps can be used to catch moths such as armyworms, cutworms, stem borers and other night flying insects. Light traps are more efficient when placed soon after the adult moths start to emerge but before they start laying eggs. 2) Colour and water traps can be used to monitor adult thrips. In some cases thrips can even be reduced by mass trapping with coloured (blue, yellow or white) sticky traps or water traps in the nursery or field. 3) Water traps should be at least 6 cm deep with a surface area of 250 to 500 cm ², and preferably round, with the water level about 2 cm below the rim. A few drops of detergent added to the water ensure that thrips sink and do not drift to the edges and escape. 4) Yellow sticky traps can be used to control whiteflies, aphids and leaf mining flies. 5) Fruit bagging prevents fruit flies from laying eggs on the fruits. In addition, the bag provides physical protection from mechanical injuries (scars and scratches).

Biological control : Biological control is the use of natural enemies to manage populations of pests (such as ladybird beetles, predatory gallmidges, hoverfly larvae against aphids and psyllids) and diseases. This implies that we are dealing with living systems, which are complex and vary from place to place and from time to time. Preventive release of the natural enemies at the beginning of each season. This is used when the natural enemies could not persist from one cropping season to another due to unfavourable climate or the absence of the pest. Populations of the natural enemy then establish and grow during the season. Releasing natural enemies when pest populations start to cause damage to crops. Pathogens are usually used in that way, because they cannot persist and spread in the crop environment without the presence of a host. They are also often inexpensive to produce. Microbial agents like bacteria such as Bacillus thuringiensis (BtThe best-known biocontrol agent used in field crops is the bacteria Bacillus thuringiensis var. kurstaki and Bacillus thuringiensis. var. aizawai against diverse lepidopteran pests, and the Bacillus thuringiensis var israeliensis against mosquitoes. Viruses such as NPV (nuclearpolyhedrosis virus), effective for control of several cater-pillar pest species. Fungi that kill insects, such as Beauveria bassiana. Different strains of this fungus are commercially available. For example: strain Bb 147 is used for control of corn borers ( Ostrinia nubilalis and O. furnacaiis) in maize, strain GHA is used against whitefly, thrips, aphids and mealybugs in vegetables and ornamentals. Entomopathogenic nematodes against different weevil species (e.g. Steinernema carpocapsae, Heterorhabditis bacteriophora) and to control soil insects like cutworms (Agrotis spp.) in vegetables.

Chemical control :
Farmers avoid the use of broad-spectrum synthetic pesticides, which severely disrupt natural control and prefer botanical insecticides to manage the insect pests. Some plants contain components that are toxic to insects. When extracted from the plants and applied on infested crops, these components are called botanical pesticides or botanicals. Rotenone ( Derris sp
.), nicotine (tobacco), and pyrethrins ( Chrysanthemum sp
.), neem, chilli pepper and garlic etc have been used widely both in small-scale subsistence farming as well as in commercial agriculture. Toxicity of botanical pesticides is usually not very high and their negative effects on beneficial organisms can be significantly reduced by selective application. Furthermore, botanical pesticides are generally highly bio-degradable, so that they become inactive within hours or a few days. This reduces again the negative impact on beneficial organisms and they are relatively environmentally safe compared to chemical pesticides.

References:

1. IFOAM. 2003. Pest and disease in organic management. A Latin American perspective. Compiled and edited by Dr. Dina Foguelman.

2. FiBL. 2011. African Organic Agriculture Training Manual - Pest, Disease and Weeds. Version 1.0 June 2011. Edited by Gilles Weidmann and Lukas Kilcher. Research Institute of Organic Agriculture FiBL, Frick

3. IFOAM. 2003. Training Manual for Organic Agriculture in the Tropics. Edited by Frank Eyhorn, Marlene Heeb, Gilles Weidmann, p 156-183, http://www.ifoam.bio/


About Author / Additional Info:
Pursuing Ph D in Entomology in Indian Agricultural Research Institute