Be Wary Of Insect ‘Clean-Up’

There are concerns and consequences associated with adding an insecticide to the spray mix just to “clean up” any insects that may be present. Have you talked with your grower-customers about these?

Lurking in every soybean field, all season long, are low numbers of various species of spider mites and aphids. These pests are rarely noticed when conditions remain “normal” due to the actions their natural enemies. However, treating fields with an insecticide may tip the balance in the favor of potential pests, according to Purdue University’s John Obermeyer, IPM (integrated pest management) supervisor and Larry Bledsoe, research assistant. This is because natural enemies recover more slowly from broad-spectrum insecticides compared with mites and aphids, which have an extremely rapid generation time.

Dry conditions exacerbate crop damage from mites and aphids. One major reason for this is because pathogens that cause insect diseases do not flourish in dry environments, the pair say. Just as crop diseases are more likely during wet/high humid conditions, so are insect diseases. An epizootic is quite impressive, as potentially damaging populations of mites/aphids are quickly and thoroughly wiped out.

Fungicides sprayed for crop diseases also control these beneficial pathogens. This is one reason why high-value crops, e.g., fruits and vegetables, receiving prophylactic (calendar sprays) of fungicide and insecticide often have spider mite flare-ups.

Ron Hammond, Ohio State University field crops entomologist, adds another point to this consequences list. Pollinators, specifically bees, are present in soybean fields. Though soybean are self-pollinating and aren’t reliant on these beneficial insects, bees will often visit fields. Pyrethroid insecticides are deadly to bees and a multitude of other pollinators. With the recent woes — e.g., mites, colony collapse, etc. — of the honeybee, further reduction in populations in only adds to the injury.

Lastly, it must be emphasized that insecticides do NOT increase yield, they only preserve it, say Obermeyer and Bledsoe. Any yield enhancing claims with insecticides are not only misleading but against the law. This one fact alone should make retailers and producers wary and monitor fields before treatments are made.

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