True white grubs and early-season corn problems

True white grubs may cause early-season stand reduction in corn. Because the past winter was extremely mild, survival of many soil dwelling insects may be much higher than during an average or colder-than-average winter. As with most soil insects, it is difficult to predict when and where true white grubs will be found. Problems can be expected in cornfields following pasture or grassy Conservation Reserve Program ground

Grasshoppers confirm mild winter

If we use grasshoppers as a gauge of winter severity then the winter of 2001-2002 was certainly an insect-friendly winter. I noted in the December 2001 Integrated Crop Management newsletter that a few differential grasshoppers had survived around Ames until at least December 8. Typically, many of these grasshoppers are dead by early November. Then, on February 23 of this year, which was an unseasonably warm day, I found grasshopper nymphs in my garden. The time span between the last grasshopper of 2001 and the first grasshopper of 2002 was only 77 days

Long-legged flies in crops

It is not unusual to find something in corn or soybeans that normally does not occur there. This year, a species of long-legged fly is abundant, especially in soybeans, but it is not a pest of either this crop or corn. The adult fly is a metallic green and copper with clear or patterned wings, and of course, long legs. Adults are common in damp woods and fields, and along streams, where they can be found running in circles on leaves

Grape colaspis in Iowa corn

The grape colaspsis, an uncommon beetle (and one that also is hard to pronounce), has caused significant problems in corn in northeastern Iowa. Jim Fawcett, Iowa State University Extension field specialist-crops, and I examined fields in Benton County in late June with stand loss problems. This past week, Jim Webster (Pioneer Hi-Bred) reported significant stand damage in Blackhawk, Grundy, and Tama counties. He stated that this problem has significantly increased during the past 3 years

Cowpea aphid: a new pest in Iowa alfalfa?

Iowa producers may have a new pest to contend with in alfalfa. On July 29, Joel DeJong, ISU field specialist-crops, and I visited an alfalfa field near LeMars that had large populations of “black” aphids as reported by Peter Westra and Todd Russ (LeMars Agri-Center, LeMars, Woodbury County). The field was suffering from drought stress and small populations of aphids were fairly easy to find. Hal Tucker (Tucker Consulting, Storm Lake) also has reported finding alfalfa fields with black aphids covering entire plants in northwestern Iowa

Soybean aphid hits eastern Iowa

On June 8, soybean aphids were being found in several Iowa locations. Brian Lang, Extension specialist-field crops, found one winged aphid on V1-V2 stage soybeans near Decorah. Virgil Schmitt, Extension specialist-field crops, also stated he had received a report of a couple of fields being sprayed for soybean aphid between Wapello and Burlington. Brian Wischmeier, NK Seeds agronomist, also on June 8, had received information that a field near Mediapolis in southeastern Iowa had large enough populations in V4-V6 stage, 14-inch soybeans that honeydew was collecting on the pant legs of the farmer as he walked the field

The Bt corn refuge: Is it really necessary?

Corn growers are increasingly adopting the corn biotech traits in YieldGard®, Herculex®, and Agrisure® for yield protection against corn rootworms and/or European corn borers in what we call Bt corn hybrids. All of these traits require that corn growers follow Insect Resistance Management (IRM) requirements to effectively manage this technology. Surprisingly, I heard numerous corn growers during my recent winter meeting circuit around the state scoff at the IRM requirements. I\u27m sure many of them were thinking, is a Bt corn refuge really necessary

Dogbane beetles are not pests

It happens at least once or twice every year; someone finds a brilliant metallic green beetle in a corn or soybean field and asks if it is a pest. The dogbane beetle is fairly large for an Iowa beetle, about 3/8-1/2 inch in length, but it feeds only on dogbane and milkweed. The larvae feed on the roots of these two plants; therefore, this insect is fairly common along roadsides, in pastures, and grassy filter strips in fields where these plants grow

Leafminer injury common in soybean

Several crop scouts have inquired about soybean leaves with brown pockets or blisters often found along the edge of the leaflet. These blisters are the chambers created by soybean leafminer larvae. Only one larva occurs in each chamber, but I have seen leaflets with as many as three chambers and larvae. I have never seen any economic damage caused by the larvae but the adults do transmit bean pod mottle virus. The adult leafminer was featured in the June 17, 2002, Integrated Crop Management newsletter, page 102

Grasshoppers and insecticides

Each year, I hear the statement that grasshoppers must be sprayed when they are small because adult grasshoppers are notoriously hard to kill. I was not certain that this statement was true, so last year I sprayed adult differential grasshoppers in a laboratory experiment. Ten adult grasshoppers were singly caged in paper cups and covered with nylon mesh for each treatment. Cups containing the grasshoppers were then sprayed in a mechanical spray chamber with an insecticide at a rate of 19.6 gallons of water per acre and 25 psi by using an 80005-E nozzle