Corn pollination time raises the stakes for insect control. Scouting over the next few weeks is crucial to determine management options and protect your yield.
Corn rootworm beetles and Japanese beetles can be big yield robbers during pollination, especially when both appear in the same field.
Densities of at least five corn rootworm adults per plant affect pollination. The threshold for Japanese beetles is three or more per plant. Treatment decisions need to be considered at these thresholds.
"With corn over $3 per bushel it doesn't take many more kernels per row to justify an insecticide at pollination if needed," says Bob Lawless, a certified crop advisor with Golden Harvest. Getting the field sprayed within a couple of days of hitting the thresholds should protect yields.
Silk clipping is the biggest concern because it can inhibit kernel production. "When 1/2 to one inch of fresh silk remains and soil moisture is abundant, successful pollination is likely occurring," says Mike Gray, an extension entomologist.
If your fields have variable growth because of dry weather then be especially cautious with your scouting since your silks may be emerging over an extended period of time, Lawless advises.
Before pollination, Japanese beetles will feed on leaves causing minimal damage. Individual beetles can live for 30 to 45 days, allowing populations to persist in a given area for several weeks.
Corn rootworms will also feed on the leaves causing a grayish, skeletonized look. That feeding will end with pollination because their preferred diet is pollen and silks.
At the same time, corn rootworm beetles will mate and lay eggs in the soil. The eggs will lie dormant over the winter hatching next spring to attack corn roots.
Scouting your fields for adult corn rootworm activity can help determine your risk in 2008. If the number of beetles exceeds one per plant, plan for control measures next year, Lawless recommends.