Aphids and rootworms and borers, oh my. Every year farmers and entomologists are on the lookout for pesky pests that can damage crops. Temperature, moisture and migration all play a role in determining which insects will show up in fields.
The following state entomologists give their predictions about what you'll face on your farm this year, and take a look back at what bugged growers in 2006.
Corn rootworms are almost always the primary insect in Illinois corn, and probably will be again in 2007, says Kevin Steffey, University of Illinois. They're a threat to corn planted after both corn and soybeans. Also, “the continued expansion of the range of western bean cutworms and their threat to corn production concerns growers in the northern half of Illinois,” he says.
For soybeans, “there is potential for large populations of soybean aphids in 2007,” Steffey says. “Large numbers of eggs overwintered, so soybean producers should watch for them early (late June, early July) and regularly.”
Last year Illinois growers dealt with corn rootworms in corn and Japanese beetles in both corn and soybeans. Along with those pests, “in western and central Illinois, significant infestations of second-generation European corn borers were much more common than they've been in recent years,” Steffey says. “Many surveyed fields had 100% infestation.”
“We expect rootworm to be the principal pest in 2007,” says Christian Krupke, Purdue University. For the soybean crop, “we're forecasting that soybean aphids may be poised for an outbreak year.”
Entomologists in several states agree with Krupke and are predicting a soybean aphid outbreak in 2007, so farmers should keep an eye on their fields.
Growers saw corn rootworm in the state in 2006 as well, but escaped any major problems in soybeans. “There was no significant pest pressure to speak of in soybeans,” Krupke says.
Iowa State University's Marlin Rice says corn rootworms and soybean aphids will be the pests to watch in Iowa this year. “As long as we plant corn, we'll have corn rootworm problems,” he says.
“I also expect soybean aphids to be back with a vengeance,” Rice says. “Aphid suction traps in several Midwestern states indicate that fall aphids laid lots of eggs on buckthorn.”
Rice says that at least 300,000 acres were sprayed with an insecticide in 2006 to control aphids, “and this was during a year when pest pressure was light.” As far as last year's corn crop, “northern and western corn rootworms always pose problems and cause crop damage somewhere in Iowa.”
For the upcoming growing season, Phil Sloderbeck of Kansas State University says, “corn rootworms will undoubtedly continue to be our number one concern on corn.”
Sloderbeck says Kansas is seeing an increase in the number of fields with soybean stem borer injury, “and there is some concern of an increased incidence of white grub damage in soybeans.”
Last year, corn rootworms were the biggest corn pest on continuous corn throughout the state. “On a more localized basis, Southwestern corn borer, spider mites and fall armyworms caused some serious damage,” Sloderbeck says.
The lack of soybean aphids, rather than any major pest problems, was a bigger story in 2006, he adds. “The hot weather of 2006 was apparently very unfavorable for soybean aphid establishment.”
“Soybean aphid overwintering egg numbers are high, so I expect 2007 to be a ‘good’ aphid year,” says Chris DiFonzo, Michigan State University. Many states' entomologists predict large aphid populations in the 2007 growing season.
DiFonzo also notes that the mild winter in Michigan this year could increase populations of other insects. “We may see higher populations of insects that overwinter locally — for example, flea beetle, bean leaf beetle and corn rootworm,” she says.
Michigan growers didn't encounter any widespread insect problems last year, says DiFonzo.
Soybean aphid has become a “chronic concern” in Minnesota, according to Bruce Potter, University of Minnesota. Growers should watch for it again in 2007. Economic infestations have occurred somewhere in the state every year since the soybean aphid's discovery in 2000.
For corn, Potter says high corn rootworm beetle populations were observed in southwest, south-central and west-central Minnesota in 2005. Last year, corn rootworm was the most significant insect problem, according to Potter, “although infestation levels were below previous years.
“Earlier, south-central Minnesota had been experiencing low rootworm damage but the extended diapause problem resurfaced further east in 2005,” he says. “Therefore, 2007 southern Minnesota corn fields that were planted to corn in 2005 or 2006 are at some risk for northern corn rootworm.”
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Wayne Bailey, University of Missouri, says two or three pests could reach economic levels in 2007. “The first is green stinkbug. Numbers of adults and nymphs were very high going into winter and may have had good survivorship due to the mild weather,” he says.
Bailey also says soybean aphids could be a problem. “If populations in the more northern states and Canada grow to predicted levels next summer, then Missouri soybeans could be at risk if north winds during late June bring high numbers into the state.”
For corn, Bailey expects some problems with black cutworm depending on moth flights in the spring. “I'm sure some infestations of corn earworm and fall armyworm will occur, but damage will most likely be moderate,” he adds.
In 2006, Missouri corn growers saw black cutworms in late spring and high numbers of corn earworms and fall armyworm in mid-summer.
“Corn rootworm populations were relatively high in many areas of Nebraska last year, so the corn rootworm will likely be a significant pest this year,” says Tom Hunt, University of Nebraska. “The western bean cutworm, banks spider mite, two-spotted spider mite, European corn borer and other corn pests all have the potential to be a problem if the conditions are right.”
Hunt says growers should scout regularly for the two primary soybean insect pests — the soybean aphid and bean leaf beetle. Doing so will allow them to notice if other pests, like various defoliators or the two-spotted spider mite, are increasing.
Last year, Nebraska farmers dealt with corn rootworm as the most significant corn pest. Hunt says crop rotation is still an effective method for managing rootworms in Nebraska. For soybeans, the soybean aphid was the most significant pest in 2006.
For North Dakota farmers, “we anticipate soybean aphids to be a problem again in 2007,” says Janet Knodel, North Dakota State University. Also, “with increasing acreage of corn anticipated in 2007, European corn borer, corn rootworm and other insect pests will need to be monitored more closely,” she says. Despite that, Knodel doesn't expect any major insect problems.
Last year, soybean aphid was the biggest insect pest on soybeans. “Aphids were found in 54% of all soybean fields surveyed, and observed from mid-June through harvest,” Knodel says. “Spider mites also became a soybean production concern late in the season.”
In corn, “very low populations of European corn borer and corn rootworm were found in 2006,” she says. “There were isolated problems with wireworms and seed corn maggots causing injury to seedling corn.”
Ron Hammond, Ohio State University, says he's especially concerned with two insects for 2007. “On corn, we anticipate greater rootworm pressure on corn following corn with the western corn rootworm, as well as problems on first-year corn in western Ohio,” he says.
“For soybeans, we're predicting that soybean aphids will make a comeback and require management in much of northern and central Ohio.”
Last year, the biggest problem in corn was also western corn rootworm, Hammond says. “We experienced some of the highest populations and pressure from root feeding by this insect that we have seen in Ohio.” The bean leaf beetle was the biggest concern in 2006 for soybeans.
“Managing corn rootworm larvae is the most significant insect pest problem for South Dakota corn producers in relation to damage losses and/or associated control costs,” says Billy Fuller, South Dakota State University (SDSU).
Fuller says the increased demand for corn-based ethanol production in the state will lead to more acres of continuous corn. “This increase, in combination with already existing problems with extended diapause in northern corn rootworm populations, could result in even greater potential rootworm injury.”
Kelley Tilmon, SDSU, says the soybean aphid will be the insect to watch for soybean growers in 2007. “My research program in soybean entomology at SDSU has recently come out with new threshold guidelines to help producers mange this pest,” she says.
Last year, Tilmon says aphids were the biggest problem in soybeans, but growers had more trouble with spider mites than usual. Fuller says corn rootworm was the most significant pest in the state for corn.
Eileen Cullen, University of Wisconsin, says they'll be monitoring soybean aphids, western bean cutworm in corn and variant western corn rootworm in first-year corn in 2007.
“Wisconsin soybean aphid trap captures during fall 2006 were low compared to states like Indiana and Illinois,” she says. “Awareness and frequent scouting will be critical in 2007 in the event that an outbreak occurs.”
For corn, Cullen says, “western bean cutworm is not yet established as an economic pest in Wisconsin, however it's expanding its range eastward in the Corn Belt. Pheromone traps statewide recorded widespread moth flight in 2006, although at relatively low numbers compared to states like Iowa.”
She also says variant western corn rootworm has changed its behavior to lay eggs in non-corn crops, like soybeans. “This presents economic risk to first-year corn fields in affected areas of Wisconsin, but not all of the state. Our research has documented the variant western corn rootworm, particularly in southeastern Wisconsin, and we'll continue to monitor for potential range expansion in 2007.”