April's Ag Advice by April Borders Summer is well on its way. Corn is pollinating and the soybeans are blooming. Life is good. But just when you think that things are going good, you find them, lurking around in your crops. It's those dreaded insect pests. It never seems like we can catch a break. So don't let your guard down too early as these creatures have just begun.
Soybean aphids are present and lurking in our fields. If you look hard enough you could probably find them in nearly all our fields. If you can't find them you might be seeing other indicator signs like ants or lady beetle larva and adults. Most fields have small numbers although there have been a couple of fields in Yankton and Clay counties that have reported numbers up to 600 aphids per plant.
As the soybeans enter their critical reproductive stages, the presence of large numbers of aphids will negatively impact yields. Soybeans are especially vulnerable to the aphid and other insects from the R2 or full-bloom stage, through the R6 or full-seed stage. Look for the soybean aphid on the growing points, stems and on the underside of the leaves. The aphids will generally infest the borders of the fields first and then spread into the whole field.
Growers should be scouting their fields every three or four days to keep up with the rapid growth potential of this insect. Cool temperatures could cause an increase in the population.
Grasshoppers are very scattered. Many areas that had above average rainfall are reporting few grasshoppers. Most producers are ignoring them because of all the good alternate vegetation that has been growing. It seems to be "keeping up" with their feeding. But don't let them fool you either. They could become a serious problem later.
Bean leaf beetles are slowly starting to be seen. Be on a look out for these guys, too. The critical stage to protect your soybeans is at full bloom.
Corn borers are becoming abundant in some areas. In the southeast, first brood moth numbers were very low and the second brood or univoltine should be watched for. This second generation larva bore into and feed on stalks, tassels and ear shanks. This can cause a reduction in dry matter production and cause broken stalks and dropped ears. To determine if there is an infestation, scout for egg masses on the ear, ear leaf and the three leaves above and below the ear.
Also be on the lookout for the Western Bean Cutworm. We are starting to see this insect in our corn fields, too. Remember that not all Bt-corn is created equal so know which type you planted and which insect you will be susceptible, too.
Scouting is the only way to know what is happening in the field. Remember to check economic thresholds and time your spraying to get the most for your money. Timing can be critical for insect control, especially with the soybean aphid. If you have questions on calculating economic thresholds or have questions about insect identification feel free to call the Clay County Extension Office at 677-7111.