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January 22, 2015

Brazilian Farmers Confronting Increased Pest Pressures

The irregular rains and high temperatures during the month of January have led to increased pest pressures in the soybean fields of central Brazil. Farmers are reporting increased applications of insecticides for the control of leaf eating caterpillars such as corn earworm in addition to white flies. The increased costs of controlling these insects is coming at a time when margins are already squeezed by low soybean prices and potentially lower yields caused by dry weather.

White flies have become a bigger concern in recent years in central Brazil. White flies are tiny snow-white insect pests that resemble moths when magnified. They suck plant juices causing yellowing of the leaves and eventual plant death if their populations are excessive. Populations of more than 15 flies per leaf can cause yield losses especially during the important pod filling period.

The problem with white flies appears to be worse in areas where cotton is grown. The cotton crop is generally harvested only a month or two before the new crop of soybeans are planted. This late harvesting of the cotton in addition to any volunteer cotton plants in the vicinity, helps to maintain the fly populations allowing the pests to move into the newly planted soybean fields.

The hot and dry weather in central Brazil over the last month has allowed the fly population to explode. Under these types of conditions, the life cycle of the fly is shortened allowing for more generations to evolve.

Scientists are stressing to farmers that control for these pests should be on a regional basis and that all the farmers in the region need to take measures to control the insect. If one farmer sprays for the insect but his neighbor does not, the insects can quickly move back into the field that was just treated.