FOOD security has always been the most strategic aim of the nations, worldwide. Food safety is a complementary module due to losses endured by a number of biotic and abiotic factors during production, handling and storage. The extent of such losses depends upon post-harvest management system and pest control measures.
Authors: Muhammad Anwar & Dr Muhammad Ashfaq
Among destructive agents, pest insects play a major role in post-harvest system of perishable and semi-perishable agricultural products. Wheat is a staple food of the people and food security-cum-safety plans include its production and protection.
Wheat production fluctuates around 20 million tons which is enough to accomplish our food, feed, and seed requirements for few years. By 2010, our wheat requirement will be about 25.5 million tons. Presently, any deficit in domestic production is compensated with imports.
According to scientists, post-harvest wheat losses range from 2.5 to 15.3 per cent depending upon the handling and storage conditions as these are high in private sector due to the unawareness about pest management protocols and uncertain storage and marketing system.
Presently, food grains are protected from pest insects by using synthetic insecticides and fumigants. In early 90’s, the Punjab Food Department controlled insect pests of stored-wheat with one tablet of Aluminum Phosphide per cubic meter volume which now is being done with three tablets for controlling the resistant strains of insects.
A considerable amount of foreign exchange is spent on the import of pesticides which can be avoided by utilising our domestic natural resources. Moreover, Codex Alimentarius Commission of the WTO recommended organic control of insect pests to make food products according to the International Standards Organization. Keeping in view the demands, it was decided to orientate the research towards organic management of pest insects in stored wheat and selected local botanicals.
In the recent past, insecticidal properties including toxicity, feeding-repellence, surface protection and oviposition deterrence were confirmed by different researchers against the insect pests of stored grains in laboratory studies. Accordingly, oils of these botanicals were used in the organic control of pest-insects with the integration of asepsis, disinfestations, and different packing materials under natural conditions in the warehouses. This was done to develop an IPM protocol for safe storage system at farm level by replacing the synthetic insecticides.
Insect-free jute and cotton bags made from the fabric of different densities (mesh sizes) were sprayed-over with four different concentrations from each of the botanical oils and mixtures in three sets for three storage periods (30, 60 and 90 days) each, with three replications.
Infestation free wheat of new crop was packed in the bags, treated with different concentrations of test materials to evaluate their antixenosis and antibiosis. The experimental units were placed in ventilated warehouses of flourmills under favourable conditions for the multiplication of stored product insects.
The concentrations showing considerable efficacy were tried as mixtures to note their effects. Absolute data, regarding mortality, penetration into the treated bags and insect population build were collected at specified intervals. After completion of the experiment, rheological tests were applied to the flour produced from the treated and untreated wheat to note changes in dough-development and sensory evaluation of chapatti.
On the analysis of data, different concentrations, storage periods and packing materials showed a significant effect upon penetration of insects into the bags and mortality of insects due to their body contact with botanical oils. The degree of antixenosis and antibiosis showed a positive correlation with the concentration of the botanicals but negative with the storage periods.
Penetration into bags was inversely proportional and insect mortality directly proportional to the density of packing materials. Mixture of three botanical oils with 10 per cent concentration of each gave effective control of the target insects for two months with a fine cotton cloth packing which decreased gradually in the third month.
Farinographic studies showed no significant changes in dough development properties of the flour made from the wheat stored in bags treated with the botanicals. Moreover, sensory evaluation proved that there was no distinguishable taste or taint found in chapatti made from the flour of the wheat packed in the treated bags.
Recommendations: Farmers can save grain, environment and capital by using the oil of castor seeds, neem seeds and rhizomes of sweet flag plant to control insect pests. Oils should be mixed in equal proportion and sprayed over jute/cotton bags to be used for packing of cleaned/insect free wheat.
The mixture may be sprayed with the help of a fine sprayer. New crop wheat should be spread on metal sheets or cemented floor in the sun up to the temperatures at 55ºC for about four hours.
These sun-heated wheat grains having moisture contents not more than eight per cent may be packed in treated bags to get a safe storage for two to three months only. If wheat is to be stored for more than three months then repeat the botanical application after every two months. Insect free new crop wheat with new treated bags and proper sealing can provide better results.
Moreover, appropriate repair, cleaning and treatment of godowns/bins are also a supplement for the success of the suggested insect pests control measure.