The potentials of Organic pesticides
By: O.Q. Ballesteros
Greenfields March 1993
Because of the high toxicity of chemical pesticides, alternative pest control methods should be explored.
Everyone agrees that chemical pesticides are necessary evil. We need these chemical compounds to protect our crops from pest. For instance, in irrigated rice fields that are not protected with pesticides, the insect pest damage could go up to as high it could.
As far as unwanted plant or weeds are concerned, the estimated yield reduction is 34 percent in transplanted rice, 40 percent in direct-seeded, rainfall lowland rice; and 67 percent in upland rice.
The pesticide market.
Because of the importance of pesticides in crop production, the sale of synthetic or chemical pesticides increased yearly from 1977 to 1991, according to the Agricultural Pesticide Institute of the Philippines or APIP. In 1977, the total sale of insecticides, herbicides, fungicides and other “icides” amounted to 252.3 million pesos. Ten years later, the total sale was more than 1.5 billion pesos.
Significantly, more than 50 percent of the insecticides and herbicides purchased by farmers went to rice protection, while 60 percent of the fungicides was used to control the diseases of vegetables and fruit crops (bananas, mangoes and pineapple). Other pesticides used included, rodenticides, miticides , molluscicides and fumigants. Except for molluscicides (chemical used to control snails in ricefields and fishponds), other “icides” are generally used to protect plantation crops like sugarcane, pineapple and bananas.
Today, there is a growing awareness of the dangers posed by chemical or inorganic pesticides to the health of people and the safety of the environment. This situation has prompted government authorities to regulate and ban the use of hardly biodegradable pesticides like the chlorinated hydrocarbons (DDT, edrin) and the tin compounds. Other toxic chemicals will ultimately be banned for agricultural use pending the use of effective substitutes that originate from organic or synthetic sources.
It must be stressed that crop protection can be attained by other methods, including proper cultural management, use of resistant crop varieties, us of beneficial insects and predators, and more effective implementation of the integrated pest management program (IPM) emphasizes the use of existing biological control agents and resistant crop varieties as well as combinations of compatible farm management practices which include the judicious use of pesticides based on the economic threshold level. Economic threshold level (ETL) refers to the level of insect population in a certain field situation at which the cost of control would roughly equal the value of crop loss.
Proper cultural management is another method of pest control. It is intended to make the environment less favorable for pest reproduction, dispersal and survival. Among these practices are thorough land preparation, adjustment of planting dates, good water management, field sanitation, and crop rotation.
Constraints of botanical pesticides. Because of the exceedingly high toxicity of chemical pesticides, alternative pesticide sources should be explored and biologically evaluated for their efficacy and economy. Among the potential plant sources are tobacco, derris, nami, or scientifically called Dioscorea hispida, neem or Azadirachta indica, mariold, chili and other plants with pesticidal properties.
Despite the hihly effective pesticidal properties of tobacco as a source of nicotine sulfate and derris because of its rotenone content, commercial production of these compounds are still not a reality. This may be attributed to inadequate raw material supply (especially) derris which is not generally cultivated or produce), lack of incentives to processors and lack of competitiveness with regard to product quality compared with synthetic or chemical materials. Nevertheless, it may be worthwhile to assess the commercial value of these botanical sources. Limited technology is available but it may not be areal hindrance to commercialization since it requires sometime to produce large quantities or raw materials. Hopefully, the technology could be fully established by the time the material are available.
Producing the raw materials . Government efforts to develop the countryside can trigger enormous entrepreneurial interest in the production of botanical pesticides. A non-government organization may spearhead this livelihood project by entering into contract growing arrangements with farmers. The NGO could serve as the linkage or conduit of contract growers and processors, marketers and, ultimately, users. The government may provide both technical expertise and initial financing.
With certain pesticidal crops like neem, for example, commercial production could be coordinated with agroforestry projects since the neem tree can be planted on rolling hills, on unproductive lands or areas, and on steep slopes where cultivation of cash crops would accelerate soil erosion. The neem tree does not require much water. In fact, it is not advisable to plant it in waterlogged areas.
All parts of the neem tree are sources of pesticides , but the seed is the richest source, followed by the leaves, then the bark and finally the wood. It takes three to four years from germination to flowering. The tree flowers twice a year, i.e. March and September. The seeds can be harvested from June to July or four to five months after flowering. AN average tree can produce as much as 350 kilogram of green leaves annually and about 50 kilograms of fruit. From 50 kilograms of fruit about 30 kilograms of seeds and 60 % are recoverable. The 30 kilograms of oil could be extracted and 24 to 27 could be made into neem cake.
Neem extracts from leaves and fruits have strong insect repellant properties. Oil from the seed can repel termites and nematodes. It also affects the food intake of insects and cause abnormal insect molting. Because of its various uses, neem derived pesticides can be classified as “broad spectrum.”
Studies from Pakistan and the use of neem as an insecticide to protect stored wheat grain show that more than 80 % of major insect pest population were controlled for more than month. The farmers used neem in any of the following method:
- Whole neem leaves were mixed with grain in gunny sack.
- ground neem leaves made in paste were mixed with mud and used for making mud bins.
- Empty gunny sacks were soaked overnight in water containing two to ten percent neem leaves (weight/volume basis) and dried before placing grain in treated sacks.
Pakistan farmers are using this technology because of its low cost, environmental safety, and steady supply of raw materials; the neem tree is grown by almost all farmers and application of the products is simple. Besides, the neem is non-toxic to humans and warm-blooded animals. Furthermore, the cost and return at the farm level revealed a high return on investment – between 300 to 600 percent on cash investments. In addition to its pesticidal properties, neem by-products can be used for soap making, preparation of epoxy compounds, tooth powders and toothpaste, to name a few.
Prospects of botanical pesticides as pointed out earlier, high crop production may be attained through the judicious application of farm inputs coupled with good farm management practices. Pesticides are a necessary production input now and they will continue to be so in the years to come. They will be needed as lon as there is a need for food, animal feeds and raw materials for industry. However, tremendous efforts have to be exerted to explore botanical environment-friendly sources of pesticides that are not poisonous to man and warm blooded animals.
The Philippines is fortunate to have endemic plant species and favorable growing conditions. We have to act fast and exploit the opportunities. The prospects are enormous inasmuch as agriculture is still the largest industry in the country. Growing pesticidal plants will provide employment opportunities in the country side and greatly reduce the importation of synthetic pesticide materials.