Orange Wheat Blossom Midge
The Basics
Orange Wheat Blossom Midge The Basics |
|
Life Cycle and Biology
Adult wheat midge laying eggs on wheat head.
Adult wheat midge are small, orange flies, about half the size of a mosquito. They have overwintered in the soil of infested wheat fields from last year. The adults emerge from the soil beginning in late June and early July. Peak activity, and the greatest risk of infestation, is expected during late June in southeastern counties and early to mid July in central and northern counties.
Wheat midge eggs.
NF and the wind speed is less than 6 mph. Eggs are laid on wheat heads around and on the florets. Eggs hatch in 4 to 7 days.Egg laying takes place after 8:30 p.m. when the air temperature is greater than 60
Wheat midge larvae feeding on developing kernel.
Larvae are orange colored. They feed on the developing kernels within the glume. No changes in external appearance of the wheat plant takes place. Larvae feed for about 2 to 3 weeks and grow to 1/8 to 1/4 inch long. They drop from the wheat heads in August after rain or heavy dew.
Wheat is the most important host plant. Barley is not considered susceptible to wheat midge.
Management Decisions for Wheat Midge
- Deciding to treat
Wheat is ONLY susceptible to midge attack between heading and flowering.
The decision to treat wheat for midge should be determined by growth stage, type of wheat being grown, and the number of adult midge found on wheat heads during the evening scouting activities.
Hard Red Spring Wheat
Treatments after 50% of the first heads have flowered are not recommended due to reduced levels of efficacy and for the protection of a parasitic wasp that attacks the midge eggs.
Durum Wheat
Treatments after 50% of the first heads have flowered are not recommended due to reduced levels of efficacy and for the protection of a parasitic wasp that attacks the midge eggs.
- When to Scout for Wheat Midge
Degree Day accumulations can be used to decide when to begin scouting fields for wheat midge adults. A North Dakota degree day map summarizing accumulations for the season is helpful in identifying when a region has emergence underway. Based on data from Canada, the threshold temperature for wheat midge development is 40 F. Observations indicate the following DD accumulations for events in the midge population.
DD
EVENT 450 the midge breaks the larval cocoon and moves close to soil surface and forms the pupal cocoon. 1300 10% of the females will have emerged 1475 about 50% of the females will have emerged 1600 about 90% of the females will have emerged.
- Identifying at risk wheat fields
Based on North Dakota field observations, midge larval infestations were the greatest when heading occurred during peak female emergence (1475 DD). When using 40 degrees Fahrenheit as a threshold for wheat development (normally wheat development is monitored with 32 degrees), heading of HRSW occurs around 1000 -1100 DD. Using this information, the following midge activity is expected based on degree day accumulations at time of wheat planting.
|
Wheat Midge Degree Days Used as a Guideline for HRSW Risk Assessment |
|
HRSW planted PRIOR to accumulating 200 DD will head before wheat midge emerge. |
|
HRSW planted FROM 200 to 600 DD will be heading at the time wheat midge are emerging. |
|
HRSW planted AFTER 600 DD will head after peak emergence and should be at low risk to midge infestation (higher risk of frost, however). |
-
How to Scout for Wheat Midge
Monitor wheat fields between heading and flowering. Field scouting must be in the evening from 9:00 pm until 11:00 pm. Wind speeds should be below 6 mph. Wheat midge ADULTS can be seen laying eggs on the wheat heads.
Monitor from HEAD EMERGENCE until 80% of the heads have ANTHERS VISIBLE. When anthers are visible, a wheat head is flowering.
Visit 3 or 4 different sites in the field. At each location, count the number of midge on several sets of wheat heads (4 to 5 heads per set). Record and calculate your average for the field.
- Other Methods for Detecting Wheat Midge
Scouting is the only recognized way of arriving at an accurate decision to treat a field. There are other methods that may be used to detect the presence of midge in a field for the purpose of recognizing adult wheat midge. None of these methods are reliable for making treatment decisions.
emergence traps - a container placed on the soil surface to collect midge as they emerge from the soil. Aids in recognition of midge and alerting a person to the start of emergence.
sticky traps - white traps, coated with oil, placed at the same height as the wheat plants. Midge adults become stuck to the traps. Aids in recognition of midge and alerting a person to the presence of midge.
pie tins, paper plates, etc. - these have been used to quickly collect adult midge in fields for aid in recognition of the insect. Apply cooking oil to the surface of the object and sweep it through the canopy of the wheat plants. Midge and other insects should stick to the surface for easier identification.
- Insecticides for Wheat Midge
Insecticides registered in North Dakota for wheat midge ares Lorsban 4E at a rate of 1 pint per acre, and Penncap-M at a rate of 2 to 3 pints per acre. Most insecticide efficacy information available is for Lorsban 4E. Ground or aerial application can provide effective control when timed properly.
Aerial - apply in a minimum of 4 gallons of water per acre. Applications should be made in the late afternoon or early evening for best results.
Ground - apply in a minimum of 10 gallons of water per acre, using 40 to 45 PSI. Angle nozzles forward at a 45Eangle. Applications throughout the evening should be effective.
Tank mixing - Lorsban 4E can be mixed with most fungicides. Avoid tin, copper, and zinc materials when mixed for greater than 12 hours. Do Not Apply with Supertin.
Timing a treatment is critical for getting the best results. Apply insecticides in late afternoon, preferably after 6:30 p.m. and when the crop is heading to flowering. The following guidelines are based on management experience when Lorsban 4E was used.
If the action threshold is reached, then consider the following:
- if 30% heading, wait up to 4 days then treat with Lorsban 4E.
- if 70% heading to flowering, optimum control should be achieved.
- if 30 to 60% of the heads are flowering (at least one anther visible), spray immediately, but control is likely to be reduced.
- if 80% of the heads are flowering, treatments are Not Recommended. Applications at this time are no longer effective because larvae will already be feeding on kernels and well protected inside the glume OR the plants are no longer as attractive to adult midge and further infestation of primary heads and first tillers is unlikely.
The wheat head on the right has flowered, yellow anthers are visable.
return to the NDSU Insect Updates
 |
||
 |
Department of Entomology, 202 Hultz Hall North Dakota State University, Fargo North Dakota
Extension Entomologist: Janet Knodel |
|
