Warm weather may mean more insects

Tuesday, March 20, 2012


University of Missouri Extension agronomy Specialist

The warm weather we are now experiencing is a lot more enjoyable than the snow and cold we had last year. But along with it are some changes in what is happening in the field. First, with the warmer weather, more and earlier insect problems may be expected. If you have wheat, you need to check for aphids. Aphid populations are present in low numbers in some wheat fields, but have reached or exceeded threshold levels in others. According to Wayne bailey, Extension Entomologist, most economic infestations have been found during the past 2-3 weeks in western and southwest Missouri fields. Aphid numbers vary greatly between fields, so each field needs to be checked. With the extended warm weather, aphids can be expected to move into more fields.

Bird cherry-oat aphid is the one causing problems. Bird cherry-oat aphids are medium sized aphids with olive colored bodies and reddish-orange patches on back at base of cornicles. Antennae, eyes, and tips or legs can cornicles are black in color. Greenbug is the other most damaging species. They are a small pear-shaped aphid, 1/16-inch in length, pale yellow to pale green in color with black legs, cornicles, eyes, and a predominant dark green line running down the length of the back. Both aphids are born pregnant, so populations can increase rapidly under the right conditions.

Corn determines its yield early in the season. Controlling weeds early is critical to producing top yields. If you apply your pre-emerge grass control herbicide after you plant, don't wait too long. You also need broadleaf control from your pre-emergence too. Chemical manufacturers are premixing grass control herbicides with various broadleaf compounds. This results in some things to watch for.

A.Ratios of products in mix -- Some atrazine premixes contain so much atrazine that you have to cut the rate to avoid potential groundwater contamination or carryover to next years' crop. Check the combination to make sure the ratio fits your soil characteristics and crop rotation plants.
B.Compatibility issues -- will the product mix effectively with other products that you wish to apply in the same application?
C.Settling out of premix components -- Anytime there are two or more products premixed in a jug or tank, there is a potential for settling out when stored for any amount of time.
D.Negative interactions with other crop protection products -- With increased concern over insects, some producers are applying insecticides in addition to using treated seed. Organophosphates insecticides like Lorsban, Counter, fortress, Aztec, Smartchoice and others can lead to a very bad reaction within your corn plants if you apply an ALS or HPPD herbicide. The more systemic the products are, the worse the issue can become. With some combinations you may reduce your yield by 50 bushels per acre. This isn't always a big deal, but why take a chance. Use a different herbicide or insecticide.