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May 8, 2014

Corn Earworms Bridge Gap between Soy Crops Surviving on Millet

Scientists in Brazil are concerned that significant populations of the corn earworm (Helicoverpa amigera) will be able to bridge the gap from one soybean growing season to the next by surviving on "winter" crops in Brazil. As a result, the corn earworm is expected to be an expensive pest to control again in the 2014/15 soybean crop in Mato Grosso which will be planted starting during the second half of September.

An alert is being sent out to farmers in the state from the Plant Protection Division of the Minister of Agriculture due to the presence of the corn earworm in millet, which is grown as a cover crop or green manure grown across the state during the dry season. In recent surveys, scientists have found corn earworm populations higher than in surveys taken last year at the same time. As many as 10 corn earworm caterpillars per square meter have been confirmed in millet in the municipality of Querencia, which is located in eastern Mato Grosso. The number of corn earworms in the municipality of Primavera do Leste located in southeastern Mato Grosso was even higher.

In Primavera do Leste the caterpillars were found in millet, but not in neighboring fields of Bt corn hybrids. A Bt hybrid of course produces a protein that kills at least 95% of the caterpillars. The millet is acting almost like a bait crop or refuse crop for the insect. While it is good that the insect is in the millet and not the corn, farmers are being urged to also make a good faith effort to control the insect in the millet. If not, it could led to large quantities of the insect primed and ready to move into the 2014/15 soybean crop as soon as it is planted this fall.

It was the second crop of millet planted in the municipality of Querencia last year that helps the worm to continue multiplying during the intra-harvest period. High populations of the insect have also been found in the states of Minas Gerais and Piaui in eastern Brazil.