As a crucial facility for ensuring food security, grain storage silos require a multi-dimensional pest control system encompassing environmental control, physical protection, chemical control, biological control, and integrated management to effectively block pest invasion and breeding pathways.
Environmental control is fundamental. Grain storage silos must maintain low temperatures, dryness, and ventilation. Low temperatures inhibit pest metabolic activity; most pests cease activity below 8°C, and some even die below -4°C. A dry environment reduces grain moisture content, lowering the hatching rate of insect eggs; generally, grain moisture content should be controlled below 13%. Ventilation systems must operate regularly to regulate temperature and humidity through air exchange, preventing the formation of localized hot and humid areas and expelling gases such as carbon dioxide produced by grain respiration, thus preventing gas accumulation that could lead to pest reproduction.
Physical protection is the first line of defense against pests. The airtightness of grain storage silos is paramount; the silo structure must be constructed using airtight materials, and rubber sealing strips must be installed on doors, windows, and vents to prevent external pest intrusion. Before storage, grain must undergo rigorous screening, using equipment such as winnowing fans and vibrating screens to remove impurities, damaged grains, and insect eggs, reducing the initial source of pests. Insect-proof barriers can be installed inside the storage area by laying fine sand, wood ash, or diatomaceous earth around the perimeter of the storage area. These particles can scratch and damage the insects' bodies, causing dehydration and death, forming a physical barrier.
Chemical control must adhere to the principles of safety, high efficiency, and low residue. Aluminum phosphide is a commonly used fumigant for grain storage silos. It releases phosphine gas upon contact with water, which can penetrate the grain pile and kill pests at all stages. When using it, the dosage must be strictly calculated, distributed at 2-6 tablets (3 grams each) per cubic meter. The storage area should be sealed and fumigated for 5-7 days, during which time personnel must evacuate. After fumigation, ventilation should be maintained until the gas concentration reaches the standard before storing the grain. Organophosphate pesticides such as malathion and dichlorvos can be applied by spraying or mixing with the grain, but the dosage must be controlled to avoid exceeding pesticide residue limits, and the grain must be circulated only after a safe interval.
Biological control offers advantages in terms of environmental friendliness and sustainability. Parasitic wasps are natural enemies of stored-product pests; for example, Trichogramma wasps can parasitize the eggs of pests such as wheat moths and rice weevils, and their release can establish a natural control system. Biological pesticides, such as azadirachtin, have extracts that interfere with the nerve conduction of pests, leading to anorexia, paralysis, and death, and are environmentally friendly. Microbial agents, such as Bacillus thuringiensis, produce toxins that specifically kill lepidopteran larvae, making them suitable for green grain storage needs.
Plant-derived insect repellents utilize natural ingredients. Plants such as mugwort, lemongrass, and camphor contain volatile oils that repel pests. Bundles of dried mugwort can be hung in corners of the storage area, or 10 bags (each containing 50 grams of a mixture of orange peel, red chili pepper, and ginger powder) can be placed per 500 kg of grain and sealed for storage; their aroma can interfere with the chemoreceptors of pests, reducing the probability of invasion. Tobacco stalks contain alkaloids such as nicotine. When chopped and spread on the grain surface or bottom of the storage silo, they can form a layer of toxic gas that inhibits pest activity.
Daily management is the key to continuous pest control. A regular inspection system should be established, with weekly checks of grain temperature and pest infestation. Pest monitoring lamps should be used to trap adult insects, and pest trends analyzed. When cleaning the storage silo, residual grains and dust must be removed to prevent providing habitats for pests. Areas already infested should be isolated to prevent the spread of pests. Simultaneously, personnel training should be strengthened, and operating procedures standardized to ensure that pest control measures are implemented effectively. Pest control in grain storage silos requires a five-pronged approach: environment, physical, chemical, biological, and management. Through multi-technology collaboration and full-process control, long-term, stable pest control can be achieved, ensuring the safety and quality stability of stored grain.
