Don't "bug out" when it comes to crop scouting
"It is best to scout crops once a week. Once every two weeks would be the absolute minimum."
By Doug Rich
Insect control begins with effective crop scouting. Producers who do their scouting need to make the most of their limited time in the field. Jeff Whitworth, Kansas State University Extensionentomologist, Bob Wright, University of Nebraska research and Extension entomologist, and Wayne Bailey, University of Missouri Extension entomologist, provide some useful advice for scouting your crops this growing season.
Wheat growers have been in the field already scouting for insects. Whitworth said, in the fall, wheat farmers scout their crop to ensure a good stand and, in the spring, they scout to protect their yield.
"In the fall, producers want to make sure they don't have aphids that could be transmitting barley yellow dwarf, fall armyworms, or Hessian fly," Whitworth said.
These insects can reduce the hardiness of the plant and make the plants susceptible to winterkill.
The late winter/early spring pests to worry about in wheat are aphids, bird cherry-oat aphids and green bugs. In Kansas, traditionally, green bugs have been a problem but in the last six or seven years, as far as wheat goes, they have not been a problem. The bird cherry-oat aphids have become more of a problem in recent years.
"Usually bird cherry-oat aphids are more of a problem in the fall because they do have the potential to transmit barley yellow dwarf, but in the spring the aphid populations can build up," Whitworth said. "We saw this two years ago, where by virtue of their feeding damage and their sheer numbers, they were retarding the normal development of the wheat plant."
The other pest to be on the lookout for is the armyworm. Whitworth said in 2007 there were populations like he had never seen before in the May-June time frame. That year the problem was a late freeze around Easter that decimated the lady beetles and beneficial wasps but it did not bother the armyworms or bird cherry-oat aphids.
"Those populations went unchecked and they created quite a bit of havoc with the wheat around the state," said Whitworth.
Whitworth said they are getting more and more Hessian fly reports from around the state but it has not become a major problem yet. In May and June, there is not much a producer can do about Hessian fly but it is good to know if they are in the fields.
"Those Hessian flies won't go away once the wheat is harvested. They will stay in the wheat stubble and will be available next fall when the wheat is planted," Whitworth said.
If no seed treatment is used, Wayne Bailey said, the first thing Missouri soybean growers should look for is the bean leaf beetle. This is the main insect pest for soybeans in the spring of the year.
"That is one we would look for, if you have the earliest planted field in your area because they will fly quite a distance to reach those fields," Bailey said.
When bean leaf beetles are on the plant, you can see the oval feeding holes in the leaf tissue. There are two generations and the first attacks seedlings as they are coming up. If there is no seed treatment, they can do a lot of damage.
Bailey said he has received a few calls this spring on seed corn maggots. These can be a problem if your soil has high organic matter or you are putting on animal manure. Then seed corn maggot flies are out in force.
White grubs can be a problem some years. Scouting for grubs needs to be done prior to planting if producers have had grubs in the past or think they might have grubs.
"Once you plant the soybeans, there is not much you can do for grubs," Bailey said.
Japanese beetle grubs are a sporadic problem and found mostly in river bottom fields with willow or cottonwood trees, where the mature beetles gather, mate and fly back to the fields.
Pod feeders can be a problem later in the growing season. Bailey said they are getting more corn earworms and soybean pod worms, as they are called, and they can do a lot of damage very quickly.
"It just takes one larva per plant to strip that plant of pods," Bailey said. "The last few years, we are seeing more and more corn earworms late in the season in the northern part of the state."
Green stinkbugs can be a problem across the state but are more of a problem in the southern part of the state. When green stinkbugs feed on the plant, they delay maturity and cause the plant to stay green into the fall.
"Treated seed will make a big difference on bean leaf beetle, which is a major pest," Bailey said. "It can also help on soybean aphids, does not do much for stink bugs and might help on white grubs but they are pretty tough."
Bob Wright said corn growers who are using Bt corn hybrids should pay attention to the refuge areas that are not protected. Depending on the Bt corn being used, those are some areas that would not have control of European corn borer or corn rootworm.
"Some areas of the High Plains may have western bean cutworm issues and in western Nebraska we are expecting pretty good grasshopper populations this year," Wright said.
USDA did a survey in the late summer and early fall that showed high numbers of grasshoppers in central and southwest Nebraska. Producers growing corn in areas adjacent to grassland or rangeland have the potential for grasshoppers to move into the crop fields.
"In the case of grasshoppers or, in some cases, spider mites that move into fields from adjacent areas, it is important to scout the borders as well as the field itself," Wright said. "If you see a population building up in the grass borders, it would be more economical to treat them in the borders before they get into the crop fields."
Western bean cutworm has been common in Nebraska but has moved to the front range of Colorado and western Kansas, according to Wright.
Corn borer numbers have dropped off a lot in the last 10 years, but Wright said they still get reports of fields that may have economic levels.
"It is something worth scouting for, still," Wright said.
It is best to scout fields at least once a week. Once every two weeks would be the absolute minimum.
"I realize people that are trying to scout their own fields have a lot of other things to do in terms of irrigation and other field operations," Wright said. "It would be better once a week, especially in the summer because insects can develop rather quickly," Wright said.
Wayne Bailey said it pays to scout the fields at least once a week, from the time you plant until the stand is established. After that, you can go once very two weeks. Bailey said it pays to take some time and at least walk the borders of the fields. Stinkbugs are often a border problem.
Jeff Whitworth said if wheat growers are doing a good job of scouting and see the aphid populations building up and there are no lady beetles, they might want to go back to that field in three to four days.
"Aphid populations can double in three to four days," Whitworth said.
Crop scouting takes time away from other jobs that need to be done during the growing season. Even if the insects pests are not at an economic level that requires some type of control, it is good to know what is out there.
Doug Rich can be reached by phone at 785-749-5304 or by e-mail at firstname.lastname@example.org.