What are the commonly used chemical control methods for stored-grain pests?

1. Pirimiphos-methyl: Pirimiphos-methyl is an internationally preferred grain protectant, with the chemical name methyl pyrimidinyl (thio) phosphate, and the usual dose for controlling stored-grain pests is generally 5 ppm.

2. Baolianglin: Baolianglin is a grain protectant developed by the Chengdu Grain Storage Research Institute of the State Administration of Grain, and it has a very good control effect on stored-grain pests, especially suitable for rural grain storage. The ratio of Baolianglin to raw grain is 1:2500. That is, each 100-gram bag of Baolianglin can be mixed with 250 kg of raw grain.

When using Baolianglin, the grain must be dry (meeting the safe moisture standard). And the grain must be free of insects or basically free of insects.

3. Fenitrothion: Fenitrothion is the main pesticide used in rural areas to control stored-grain pests. It is a highly effective, low-toxicity, low-residue insecticide. Fenitrothion has a long efficacy and is very effective against stored-grain pests such as the maize weevil, sawtoothed grain beetle, flat grain beetle, and angoumois grain moth. Fenitrothion is high-purity malathion used for mixing with grain; be careful to mix evenly, and it is best to mix the pesticide on the drying yard before the grain is put into storage. A spray method can be used to evenly spray a 20 ppm fenitrothion solution onto the grain. The grain moisture should be within the safe moisture standard, that is, a water content below 13%. It is forbidden to mix fenitrothion with dichlorvos, otherwise it will produce a synergistic toxic effect.

After application, there should be a four-month safety interval before it can be processed for consumption.

4. Guchongjing (grain protectant)

Guchongjing is a compound plant-based insecticide made mainly from 4 to 6 kinds of Chinese herbal medicines, with a small amount of chemical agents added. It has strong repellent, deterrent, and contact-killing effects on pests. It has the fragrant odor of Chinese herbal medicines. Its insecticidal effect is remarkable. The ratio of Guchongjing to raw grain is 1:2500, that is, each 200-gram bag of powder can be mixed with 400-500 kg of raw grain.

5. Aluminium phosphide (fumigant)

What farmers commonly use for stored grain is aluminium phosphide tablets, each about 3 grams. The dosage is generally calculated at 1-2 tablets (3-6 grams) per cubic meter. Generally, 5 tablets are used per ton (1000 kg) of grain. When applying, first put the tablets into small cloth bags (one tablet per bag), tie the cloth bags tightly with rope, and evenly bury them in the grain pile to allow hydrogen phosphide to be released slowly. After application, immediately seal the grain (with special attention to sealing the bottom and surrounding areas) to ensure effectiveness. After fumigating for 5-6 days, ventilate for 3-5 days, then take out the cloth bags, choose a place far from water sources, dig a pit, and bury them deep in the soil.

The above pesticides are only for use during storage of raw grain and seeds; finished flour and rice must not use them.