Contact poisons may also act as a stomach poison if ingested. Biological-a pesticide formulation containing parasitic microorganisms such as viruses, bacteria, fungi, protozoans, nematodes, or their products that control the peat. Desiccants are absorptive dusts which scratch, absorb, or abrade the waxy surface of the exoskeleton causing death by dehydration. Silica gels are examples. Preservatives are normally poisonous substances applied to materials such as wood to protect from destructive pests.
Repellents are compounds which actively repel pests and, thus, deter attack.
Chemosterilants are substances that chemically sterilize pests thus, reducing reproductive potential. Some sterilants are specific for soil dwelling animal species. Fumigants in this category are often used to control both plant and animal life. The University of Iowa. All rights reserved.