Modern pesticides
Introduction
The discovery of DDT in 1939 by Paul Muller has ushered a new era in pest control. Thereafter, the chemical control became popular due to immediate and spectacular effects. Today, the use of chemical pesticides remains one of the best known and most widely used pest control tactics. The trend in pesticide consumption in India during the period 1954-89 shows that it has risen form 434 MT (technical grade) in 1954, to 75, 418 MT in 1989. The total demand for insecticides in India by the year 2000 is expected to be around 1,00,000 MT for agricultural and 44,000 MT for public health. The average per hectare consumption of pesticides in India has risen from 15.4 g/ha in 1960-61 to 450 g/ha in 1989-90 .
The use pattern of pesticides reflects that cotton alone consumers 44% pesticides to the total value of as 247.20 crores. This is followed by rice, which accounts for 23%. These two crops consume more than two thirds of the total quantity of pesticides in the country. Among the states Tamil Nadu, Andhra Pradesh, Uttar Pradesh and Maharashtra are using maximum quantity of pesticides. These four states alone utilize about 48.8% of the total pesticides. Conventional pesticides were successful in controlling insect pests during the past five decades, minimizing thereby losses in agricultural yields. Unfortunately many of these chemicals are harmful to man and beneficial organisms and cause ecological disturbances. In 1962 Rachel Carson published her book "Silent Spring" where she has given emphasis on misuse and overuse of pesticides on the environment. In India at present 143 insecticides have been registered, 18 pesticides refused for registration, 20 pesticides were banned & the use of 13 were restricted and 25 pesticides were under review. Besides, adverse effect on environment, the drawbacks in use of the pesticides includes development of resistance and increasing costs of pesticides.
Resistance is the development of an ability to tolerate a dose of an insecticide, which would prove lethal to the majority of the individuals in the normal populations of the same species. Since, the first report of development of resistance in San Jose scale in 1908, more than 500 species of insects and mites have developed resistance to insecticides. High levels of resistance to many insecticides have been reported in important pests viz. Heliothis, Spodoptera, Plutella xylostella, Tetranychus etc. The rapidly developing resistance to number of insecticides provided the impetus to study new alternatives and more ecologically acceptable methods of insect control as part of IPM programs. One of these approaches which have captured worldwide attention is the development of compounds with novel modes of action and acting selectively on some groups of insect pests.
Neurotoxicants
Neuroactive compounds have been the dominant insecticides for 50 years, and this is not expected to change in the foreceable future. They have direct action on nervous system; for instance DDT and pyrethroids suppress Na+ ion permeability of the nerve membrane, organophosphates and carbamates inhibit actylchoiinesterases, nicotine and cartap hydrochloride act through cholinergic (nicotinc) receptors, cyclodines and avermectins act on the postsynaptic membrane receptors (mostly on the C1-channel of gamma aminobutryric acid receptor). The conventional neuroactive insecticides were effective, inexpensive and often persistent, ideal properties for the selection of resistant strains. Further, cross resistance was more frequent within these groups because of similar pesticides. (Cytochrome P450, Aliesterases and other hydrolyses and Glutathione S-transferase). Resistance problems with this first generation of neuroactive insecticides promoted the search for new neurotoxicants acting at different sites to circumvent cross resistant.
GABA agonists
The avermectins affect invertebrates by potentiating the ability of neurotransmitters, such as glutamate and/or GABA, to stimulate and influx of chloride ions into nerve cells. The chloride ion flux produced by the opening of the channel into neurons results in loss of cell function and disruption of nerve impulses. Consequently, invertebrates are paralyzed irreversibly and stop feeding. The avermectins do not exhibit rapid knock down effect. The safety of avermectin to mammals is due to (I) the lack of glutamate-gated chloride channels in mammals (II) the low affinity of avermectins for other mammalian ligandgated chloride channels and (III) their inability to readily cross the blood-brain barrier.
The mode of action of avermectin is opposite to that of cyclodines, which are GABA – gated channel blockers.
Nicotinyl Insecticides
Nicotinyl insecticides interact with nicotinic acetylocholine receptors (nAChR) at the central and peripheral nervous systems, resulting in excitation and paralysis, followed by death.
Herbal
Pesticides
Neem Based Project
The mean tree is now in Limelight after the Western Scientists took international patents on neem products. There is a widespread belief that Neem based pesticides are for better than chemical pesticides.
The Government has already banned DDT, BHC and placed some other pesticides like monocrotophos on watch list.
Bio-pesticides are increasingly used. Neem based pesticides have excellent potential in view of the low cost, abundant availability of raw material and eco-friendly nature of the product.
About the product and market size: Active agent in Neem is azadiracthin. Neem has antifeedent and repellent properties against number of insects. Central Insecticide Control Board has approved registration of neem pesticides for commercial use.
Neem cake and bitter can be used for coating of Urea. At present, there are @ 40 units registered with CIB for manufacture of neem based pesticides. They produce @ 3000 kilolitre of pesticides valued at @ 30 crores. According to expert’s opinion, this demand can increase 10 times in a short period of 5 years. Most of the units are located in A.P., Karnataka and Maharashtra. Apart from these units there are many small units in unorganized sector. Some of these units are exporting their produce to developed countries also. Neem pesticides are at present used on cotton, rice, redgram, groundnut, soybean, vegetable fruits and tea-cake is used for all horticulture and plantation.
Above crops are cultivated in 90 million hectares. If 10% of this land is brought under neem pesticides and cakes, @ 60 million litres of pesticides and 25 Lac tonnes of neem cake will be required.
RAW MATERIAL: Neem trees are seen throughout the country. The basic raw material for neem pesticides is neem seeds. It is estimated that the potential of neem oil in the country is of the order 100,000 tonnes.
Neem seeds/fruits are collected during May-August, sun dried and stored till Oct-Dec. When these are extracted. Fruit collection is now very nicely organized in A.P., Tamil Nadu, and Maharashtra. Following problems are experienced in collection of Fruits (A) harvesting period is small, (B) fruits contain lot of moisture and hence deteriorate quickly during storage. (C) Oil is smelly. But by adopting better practices, these problems can be overcome.
Marketing of Neem Products: These products have good potential. But efforts are needed to realize the potential. There is tremendous scope for using Neem products in organic farming. Neem Pesticide consumption has doubled in tea-estates during last few years. This was due to insistence of importing countries on pesticide residues.
Many small units in unorganized sector market neem oil as pesticide without CIB registration. They do not control temperature during crushing, as such there is not azadirachtin in their samples. Such oil is useful for soap industry, but has little value as pesticide.
The market for pesticides will increase, as the farmers become aware of benefits and also due importers insistence on residues.
Though developed countries encourage bio-pesticides, their registration formalities are expensive. At present, neem based products are exported to few green-houses.
NEEM BASED PRODUCTS;
- Neem Oil – used in insecticide formulation and soap industry and health care products
- Neem cake – for soil enrichment, to improve effectiveness urea.
Process – There are different routes for producing azadirachtin depending on plant size and product ratio
Project Profile : For processing 10,000 Tonnes fruits per annum
Land: -3 Acres
Building: – 10,000 sq.feet.
Plant & Machinery: – Rs. 3 Crores
Production:
- Cake – 7,200 tonnes
- Oil - 240 KL
- Formulation – 580 KL
Breakeven point = 48% of production.
Above project profile is for a medium scale unit. However, smaller units are also
feasible.
Companion planting to manage crop pests
African marigold is known to destroy nematodes in the soil.
With increasing awareness about the toxic and deleterious effects of chemical insecticides, farmers are looking into eco-friendly options to manage crop pests. Botanical insecticides, cultural practices and bio-control agents come in handy for them to keep the pests at bay.
Companion planting with repellent and trap crops is one among the safe, but sure ways to manage the insect pests of crops. Trap crops planted along the borders and on bunds help in attracting the key pests of crops, and the crop is removed along with the concentration of insects so that the main crop is saved from pest ravage. Repellent crops are plants with strong natural aroma with which they drive away the insect pests.
A number of plants such as African marigold, castor, coriander, legumes and certain cereals are grown extensively as trap crops to protect the main crop from sucking and chewing pests such as aphids, thrips and borers. African marigold (Tagetes sp) is grown along with tomato to trap Helicoverpa armigera and thrips. Similarly castor is raised along the borders of groundnut to lure the serious insect pests.
The popular repellent crops are garlic, onion and fennel. These plants are raised as intercrops in alternate rows with the main crop to ward off the pests. Traps crops and repellent crops are widely used in garden land crops where vegetables are grown. They are employed by practitioners of ecological agriculture and bio-dynamic gardening. In dry land, some tall growing cereals are grown with groundnut, which help to attract all the major pests. The pests are then mechanically collected from these `antenna' crops, and destroyed.
Besides managing crop pests, the companion crops have also been found to help in arresting the spread of weeds. They also help to repel some soil-borne pests such as nematodes. African marigold has been known to destroy nematodes, and because of this property it is included as a companion crop in nematode infested fields, according to experts.
A number of such plants are being used in traditional agriculture, and now researchers and innovative farmers are delving deep in to the time honoured farming practices to dig out many such ecologically sound and economically viable solutions to tackle the crop pests.
The companion crops would blend well in the integrated pest management strategies for several high valued horticultural and plantation crops, and in the context of organic certification and export of premium organically grown agricultural commodities, such practices will be considered a boon for the farmers, according to experts.
(Courtesy- The Hindu, August 23)
website : www.hinduonnet.com
Ag.
Technologies
(Pest Mgmt.)
