Insect Pests to Watch Out For In Field Crops in 2011

Posted: April 25, 2011

There are always plenty of different kinds of insect pests that will attack field crops in any growing season. Some are seen every year, some seem to come in cycles and every so often a new pest finds its way into our area that we have not been familiar with before.

The Brown Marmorated Stink Bug falls into the later group and there is certainly no need to use this article as a means to create awareness of it. It has had a devastating effect on fruit and vegetable crops and an effort to better understand this insect and formulate recommendations to growers is underway. Unfortunately, there is a shortage of knowledge of how to best manage this insect in grain crops.  We do know that the insect is easier to control at smaller stages so field scouting should be started early in the season. Populations tend to build up on field edges first so scouting should be targeted there. Pyrethroid type insecticides seem to be the most effective on this insect and several products are labeled for use on soybeans.

The Western Bean Cutworm has been working its way eastward from the central plains states since the early 2000’s.  Its presence in Pennsylvania was first documented in 2009, mostly in Erie County.  Its name comes from the damage it inflicts on dry beans but has the potential to do major damage on field corn, sweet corn and pop corn.  To what extent this potential will be realized is not known.  Bt traits in corn hybrids vary in the degree of effectiveness they have in keeping the Western Bean Cutworm under control.  With the low level of infestation at this time, this is not critical. However this may be something that will become more important in hybrid selection if the population of this insect continues to grow in our area. A fact sheet about the Western Bean Cutworm can be accessed at

The cereal leaf beetle is not a new pest but one that tends to come and go in cycles.  Entomologists believe that we are in the upswing part of the cycle this year and advise small grain growers to keep an eye on their fields for possible damage.  The damage is done by the larval stage of this insect.  The larvae are active now and damage will increase as they continue to get larger. As small grain crops develop, it is critical that fields be checked for this insect as the plants approach flag leaf stage as it is very important to prevent feeding damage on this part of the plant.

Populations of the soybean aphid has bee low in even numbered years and high in odd numbered years so if this pattern continues we should be on the lookout for this pest to be a problem in 2011.  Soybean aphids move in to Pennsylvania from the upper mid-west states so are not normally a problem until mid-late July.  Natural control from various species of ladybird beetles has done a good job of keeping the soybean aphid under control (The Asian multicolored lady beetle efficiently consumes aphid at a rate of up to 200 aphids a day). Quite often we see populations of this insect begin to drop off about the time they are getting to economically damaging levels and control with insecticides is not needed. So it is important to not apply an insecticide to soybean fields earlier in the season as a tank mix with herbicides. Soybean aphid populations are probably not that high at that time and the residual of the insecticide will not last long enough to provide control later in the summer. This could in fact make the situation worse by killing off the beneficial insects that might have otherwise kept them under control. 

Factsheets about the soybean aphid, cereal leaf beetle and brown marmorated stink bug can be found at or can be obtained by contacting your local Penn State Extension office.

John Rowehl is the Penn State Cooperative Extension Regional Agronomy Agent for Grain Crops serving the Southeast Region. 

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