Oklahoma wheat farmers have a new resource to battle greenbug infestations.
Tom Royer, Oklahoma State University Extension entomologist, says a new sampling tool, Glance ‘n Go, available through the Cereal Aphid Expert System, “helps producers learn more about cereal aphid management, including how to assess natural enemies and how to determine economic thresholds for treatment.
“Wheat fields are beginning to green up in Oklahoma,” Royer says. “And that means greenbug season soon will be upon wheat producers.”
The Expert System is located at http://www.pswcrl.ars.usda.gov/gbweb/index.htm.
“The Economic Threshold calculator was developed from research conducted over a six-year period,” he says. “It allows a producer to determine a treatment threshold for greenbugs based upon the amount of injury actually caused by greenbugs, the potential value of the crop, and the cost of control. It represents a huge advance in aphid management in wheat compared to the currently available recommendations.”
Royer says the Glance ‘n Go system was developed from two years of research in more than 100 wheat fields. “It's a sequential sampling system, also called presence/absence. With it, a producer can determine if the treatment threshold has been exceeded by simply keeping track of infested tillers. It is simple and quick.”
Royer says he ran pilot tests on the system on 70 fields in 2004. “A sampler spent, on average, nine minutes sampling a field to make a decision to treat or not treat. We are continuing to improve the system, so a producer can determine the level of natural enemy activity in a field while sampling for aphids.” (Beneficial insect numbers) can be a part of a decision to treat or not treat.
“We are also pilot testing the newest version, which incorporates the natural enemy assessment this year. Our future plans include developing a Glance ‘n Go system for Russian wheat aphid.”
Royer and colleagues have developed the following question and answer format for the new resource.
The Cereal Aphid Expert System and Glance ‘n Go Sampling for Greenbugs:
Questions and Answers
Developed by: Tom A. Royer and K.L. Giles, Department of Entomology and Plant Pathology, Oklahoma State University; N.C. Elliott and S.D. Kindler, USDA-ARS, Stillwater, Okl.
What exactly is the Cereal Aphid Expert System?
The Cereal Aphid Pest Management Expert System is a set of computer programs designed to help the user manage cereal aphids in winter wheat. It was developed through the cooperative efforts of the USDA Agricultural Research Service, Site Specific Technology Development Group of Stillwater (SST), and Oklahoma State University through a grant provided by the Oklahoma Center for the Advancement of Science and Technology (OCAST).
This expert system has a Greenbug Economic Threshold Calculator, which will compute a treatment threshold for greenbugs based upon data the user provides. It also allows the user to print a Glance ‘n Go sampling form he can use for multiple fields. Treatment thresholds calculated by this expert system are precise because it uses historical weather data to predict growth rates of greenbug populations as it calculates treatment thresholds. In addition, it has an Insecticide Selection helper, an Aphid Identification helper, and a Natural Enemy information module.
What is Glance ‘n Go Sampling?
The Glance ‘n Go sampling system for greenbugs is designed to help a user accurately and rapidly sample wheat for greenbug infestations. It is based upon data taken in more than 100 wheat fields in Oklahoma over a two-year period.
Glance ‘n Go requires the field scout to keep track of the number of tillers infested with greenbugs instead of counting their actual numbers. This strategy works well when we want to know if the number of greenbugs is below or above a set treatment threshold. It is a fast, easy and proven technique for sampling insects. The Glance ‘n Go sampling system can reduce sampling time by 25 percent or more, yet is as reliable as directly counting the insects in the field.
How will Glance ‘n Go benefit my wheat production operation?
Research shows that greenbug infestations can cause economic loss long before they cause visible injury to the wheat plant. Glance ‘n Go is designed to save a wheat producer time and money. By checking a winter wheat field with this system, a grower can detect greenbug infestations quickly and make control decisions based upon the value of the crop and the costs needed to produce it.
Why do I have to use a different sheet for fall and spring?
The time of year is important because research shows that in the fall greenbugs are distributed within the field in a different pattern compared to the spring. This makes sense, because in the fall greenbug outbreaks usually develop from winged individuals that fly into fields from other crops or grasses. Spring infestations typically develop from existing greenbugs that successfully overwintered in the wheat field.
The treatment threshold is based upon the yield loss caused by greenbug feeding, the cost of control, and the value of the wheat crop. The estimated yield loss caused by greenbugs was determined from research conducted in Oklahoma over four years.
Why do I have to calculate a treatment threshold?
The other two factors, control costs and wheat value can change from year to year, field-to-field, and producer-to-producer. For example, in one year wheat may be worth $2.20 a bushel and in another it may be worth $4 per bushel.
The control costs can vary with the price of the pesticide and the cost of application. A producer who owns spray application equipment could spray a field at a lower cost per acre than a producer who has to pay for a custom application. The treatment threshold in Glance ‘n Go accounts for all of those factors and reflects their values.
Does the treatment threshold work for wheat at different stages of growth?
The treatment threshold used in Glance ‘n Go can be used on wheat only after it reaches the four-leaf stage. It is not appropriate to use it on seedling wheat, because greenbugs can kill seedlings. Results show that once the wheat plant reaches the four-leaf stage, the amount of injury caused by greenbugs is independent of plant height or other factors. The research used to develop this system provided no reason to adjust greenbug treatment thresholds based upon the size of the plant.
Does Glance ‘n Go work for other cereal aphids?
Glance ‘n Go is designed only for the greenbug, which is the most important aphid pest of wheat in Oklahoma. Research is under way to determine the amount of yield loss caused by the birdcherry-oat aphid. When the research is completed, Glance ‘n Go may be modfied to include both aphids.
Does Glance ‘n Go account for natural enemy activity?
The latest version of Glance ‘n Go accounts for activity by the parasitic wasp, Lysiphlebus testaceipes, on greenbugs by accounting for presence of mummies in the field. Although ladybird beetles can dramatically reduce greenbug numbers, predicting their impact on greenbug numbers has proven to be more difficult, and at present, does not hold much promise for use in Oklahoma.
Why do I have to walk at least 15 paces between samples?
The Glance n' Go system will accurately evaluate a field if directions for collecting samples are followed. That includes taking a representative sample of the field. To assure that representative samples are taken, the sampler should: (1) not look at tillers before they are collected, and (2) sample a large portion of the field.
Taking 15 paces between samples increases the odds that the field is being adequately sampled. Large fields (larger than 100 acres) should be regarded as two fields and sampled separately to make a decision.
Remember, this tool is only as good as the information used to make a decision. Shortcuts will make this sampling tool much less useful!
Where can I get more information?
Contact your local County Extension Office. Extension Educators can access the Glance ‘n Go system and are well versed on its use. You can also obtain a Glance ‘n Go scouting form from the Entomology and Plant Pathology Web site at http://entoplp.okstate.edu/ by selecting “Agriculture Models” then “Cereal Aphids Pest Management” and following instructions for printing a copy.