Is an insect always a pest?

    | July 28, 2014

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    This week’s story from Liberia shows the kind of damage that can happen when insect infestations are serious and spiral out of control. But is an insect always a pest? Should you always use pesticides when you see insects?

    Farmers need to assess at what point spending money on pest control is justified. If a farmer spends money on a pesticide to control pests that are doing only a small amount of damage, he or she may actually lose money. To minimize damage, farmers should examine their fields regularly to monitor pest populations, and apply controls only when infestations reach the level of “economic damage.” “Economic damage” is defined as the point at which insect damage causes a loss of income greater than the cost of buying and applying a pesticide or other control measure.

    Our script of the week shows that pesticides and other pest control methods may not be necessary if the damage caused to crops is minimal. You may want to talk to an agricultural extension worker to find out what the economic damage levels are for commonly grown crops in your region, and include this information in your broadcast. This will help farmers in your listening audience to better understand the concept of economic damage.

    For example, farmers in Guatemala learned how to test for economic damage levels in stored beans. They were taught to check samples of stored beans every 30 days for weevil damage. If more than four of every 100 beans (4%) were damaged, the farmers were advised to control the pest. If the percentage of damaged seeds was less than four percent, there would not be a significant reduction in germination, nutritional quality or sale price of the beans.