Wheat Midge Risk Maps

Dry conditions in 2023 keep wheat midge forecast low for 2024

“Soil samples in North Dakota indicate low populations of overwintering wheat midge larvae (cocoons) for the 2024 season,” says Janet Knodel, North Dakota State University Extension entomologist. “This is good news for North Dakota wheat farmers, reducing their inputs for wheat midge management.” 

A total of 2,060 soil cores were collected from 22 counties in the fall of 2023 to estimate the statewide risk for wheat midge in the 2024 wheat growing season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples. 

Wheat midge was positive at only 20 field sites (10% of the sites) in eight counties including Cavalier, Nelson and Towner Counties in the northeast, Bottineau, Pierce and McHenry Counties in the north-central region, McLean County in the west-central region, and Ward County in the northwest. These sites had low levels of wheat midge cocoons (1-200 cocoons per square meter) which does not cause yield loss in spring wheat. No soil samples had moderate or high cocoon densities of wheat midge (201 to over 800 midge larvae per square meter) which could cause economic losses in spring wheat.

Wheat midge was positive at only 20 field sites (10% of the sites) in eight counties including Cavalier, Nelson and Towner Counties in the northeast, Bottineau, Pierce and McHenry Counties in the north-central region, McLean County in the west-central region, and Ward County in the northwest.

“The majority of the soil samples had zero wheat midge cocoons in the soil for the past four years (90% in 2023, 97.5% in 2023, 95% in 2021 and 86% in 2020),” says Knodel. “We believe that the populations of wheat midge are low due to the extended drought in northern North Dakota over the past several years. Populations could return to higher levels once the drought subsides and we return to more normal rainfall.” 

Dry conditions will delay when wheat midge larvae drop out to the soil for overwintering in late summer. During drought, larvae will remain in the wheat head and are often harvested with the grain, ending up in the grain truck or bin. Dry soil conditions also increase wheat midge mortality by making it difficult for the larvae to dig into the soil for overwintering and by exposing them to predators on the soil surface. 

“With the very low populations of wheat midge for the fourth year in a row, scouting for wheat midge will be most important in continuous wheat fields, and/or when moist weather occurs in late June to early July which favors wheat midge emergence and survival,” advises Knodel. “Wheat midge cocoons also can remain dormant for several years and adults then emerge when soil moisture is adequate. These factors can cause rapid increases in the numbers of emerging adult wheat midge. The most critical time to scout spring wheat for adult wheat midge is from heading- through the early-flowering stages.”

Knodel recommends that farmers use the wheat midge degree-day model to predict the emergence of wheat midge and to determine when to scout, and if their wheat crop is at risk. Producers can access the wheat midge degree-day model on the North Dakota Agricultural Weather Network (NDAWN) website at https://ndawn.ndsu.nodak.edu/.

Select your nearest NDAWN station and enter your spring wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing and percent of wheat midge emerged. 

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Knodel points out that the beneficial parasitic wasp that attacks and kills wheat midge is dependent on its host, wheat midge, for its survival. Since few wheat midge cocoons were detected, only one site had parasitic wasps in the 2023 soil samples with 100% parasitism in Nelson County. No parasitized cocoons were found the previous two years (2022 and 2021). 

Only one site had parasitic wasps in the 2023 soil samples with 100% parasitism in Nelson County.

“Parasitic wasps play an important role in natural control of wheat midge and parasitize the eggs or larvae,” adds Knodel. “In contrast, the parasitism rate was 15% in 2020, 36% in 2019 and 9% in 2018.”

NDSU Extension county agents collected the soil samples and larval cocoons are extracted by the NDSU Extension Entomology laboratory. The North Dakota Wheat Commission supports the wheat midge larval soil survey.

Low forecast for wheat midge continues into 2023

Soil samples from North Dakota counties indicate low levels of overwintering wheat midge larvae (cocoons) for the 2023 season.

A total of 2,040 soil cores were collected from 22 counties in the fall of 2022 to estimate the statewide risk for wheat midge for the 2023 spring wheat growing season. The risk for wheat midge is based on unparasitized cocoons found in the soil samples.

The majority of the soil samples had zero wheat midge cocoons in the soil for the past three years. The percentage was 97.5% with no midge cocoons in 2023, 95% in 2022 and 86% in 2021. This is the record low since the wheat midge larval survey for overwintering cocoons started in 1995.

Only about 2.5 percent of soil samples were positive for wheat midge cocoons, with density ranging from 36 to 143 cocoons per square meter. This is a low risk for wheat midge infestation, which is classified as one to 200 midge cocoons per square meter. 

Low risk areas were scattered in eight counties throughout the state, including the northwest area (Burke County), north-central area (Benson, McHenry and Rolette Counties), and the west-central area (McLean County).

No soil samples had moderate or high cocoon densities of wheat midge (201 to over 800 midge larvae per square meter).

This dramatic decrease in wheat midge populations since 2019 is probably due to drought in 2020 through 2022. Drought can cause wheat midge to overwinter for two years instead of the typical emergence during the following season. Larvae also are susceptible to dryness and require rain to emerge from the soil in late June through mid-July, and to drop out of the mature wheat heads and dig into the soil to overwinter as cocoons. In some locations, wheat midge larvae remained in the wheat heads during harvest due to the dry environment and ended up in the harvest trucks instead of the soil. Comparing precipitation from May through August with wheat midge cocoon densities for each surveyed county over the past 12 years shows a strong positive correlation between precipitation and wheat midge populations.

Another reason wheat midge infestation risk is so very low could be due to the late spring wheat planting in 2022 due to the cool, wet conditions in early May. Late planting dates reduce the risk of infestation due to the wheat heading after peak emergence of wheat midge.

With the very low populations of wheat midge for the third year in a row, night scouting for adult midges in spring wheat fields is not pressing, unless the field is continuous wheat and/or favorable moist weather in late June to early July occurs during emergence. These two factors can cause rapid increases in the numbers of emerging adult wheat midges, especially in areas that did receive adequate precipitation last year.

It is recommended that producers still use the wheat midge degree-day model to predict the emergence of wheat midge and to determine when to scout, and if their wheat crop is at risk.

Producers should still use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

This forecast is favorable for growers since the risk for yield loss and reduced grain quality from wheat midge is low. Unfortunately, the bad news is that the beneficial parasitic wasp that attacks and kills wheat midge can’t survive without its host. No parasitized cocoons were found in 2022 and 2021. This is the second time that no parasitic wasps were observed.

Parasitic wasps play an important role in natural control of wheat midge and parasitize the eggs or larvae. In contrast, the parasitism rate was 15% in 2020, 36% in 2019 and 9% in 2018.

Drought Reduces Wheat Midge Populations for the Second Year in a Row

Soil samples in North Dakota indicate lower levels of overwintering wheat midge larvae (cocoons) for the 2021 season.

A total of 2,070 soil samples were collected from 22 counties in the fall of 2021 to estimate the statewide risk for wheat midge in the 2022 wheat growing season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

The majority of the soil samples had zero wheat midge cocoons in the soil for the past two years. The percentage was 95% with no midge cocoons in 2022 and 86% in 2021. This is the record low since the wheat midge larval survey for overwintering cocoons started in 1995. In 2018, we had another low year with 84% of the soil samples with no cocoons.

Only about 5% of soil samples were positive for wheat midge cocoons, the density ranging from 36 to 71 cocoons per square meter. This is a low risk for wheat midge infestation, which is classified as one to 200 midge cocoons per square meter.

Low risk areas were scattered in eight counties throughout the state, including the northwest area (Divide, Mountrail and Renville Counties), north-central area (Bottineau, Benson and Pierce Counties), the west-central area (McLean County) and the northeast area (Ramsey County). No soil samples had moderate or high cocoon densities of wheat midge (201 to over 800 midge larvae per square meter).

This forecast is good news for growers since the risk for yield loss and reduced grain quality from wheat midge is low. The bad news is that the beneficial parasitic wasp can’t survive without its host, wheat midge. No parasitized cocoons were found in 2021. This is the first time that no parasitic wasps were observed.

Parasitic wasps play an important role in natural control of wheat midge and parasitize the eggs or larvae. The parasitism rate was 15% in 2020, 36% in 2019 and 9% in 2018.

According to Janet Knodel, North Dakota State University Extension entomologist, the dramatic decrease in wheat midge populations since 2019 is probably due to drought in 2020 and 2021. Drought can cause wheat midge to overwinter for two years instead of the typical emergence during the following season. Larvae also are susceptible to dryness and require rain to emerge from the soil in late June through mid-July, and to drop out of the mature wheat heads and dig into the soil to overwinter as cocoons. Comparing precipitation from May through August with wheat midge cocoon densities for each surveyed county over the past 11 years shows a strong positive correlation between precipitation and wheat midge populations.

With the very low populations of wheat midge for two years in a row, producers may not have to scout for adult midges this year unless the field is continuous wheat, and/or favorable moist weather in late June to early July occurs during emergence. These two factors can cause rapid increases in the numbers of emerging adult wheat midges, especially in areas that did receive adequate precipitation last year.

Producers should still use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Dry Weather Decreases Risk for Wheat Midge in 2021

Soil samples in North Dakota indicate lower levels of overwintering wheat midge larvae (cocoons) for the 2021 season, says Janet Knodel, North Dakota State University Extension entomologist.

A total of 2,050 soil samples were collected from 22 counties in the fall of 2020 to estimate the statewide risk for wheat midge in the 2021 field season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

The majority of the soil samples, 86%, had zero wheat midge cocoons in the soil. This is the record low since the wheat midge larval survey for overwintering cocoons started back in 1995. In 2018, we had another year with 84% of the soil samples with no cocoons

Twelve percent of the soil samples were at low risk, with one to 200 midge larvae per square meter.

Scouting for adult midges always is recommended because wet weather can cause rapid increases in the number of midges during emergence.

The moderate risk level (201 to 500 midge larvae per square meter) was observed in 1.5% of the samples.

Moderate risk areas were scattered in three counties throughout the state, including the central area (Wells County), the west-central area (Mountrail County) and the northwestern area (Divide County). 

Only 0.5% of the soil samples had very high population densities of wheat midge (greater than 800 midge larvae per square meter). The hot spots were located in south-central Divide County, close to the Williams County line and southeastern Mountrail County.

According to Janet Knodel, North Dakota State University Extension entomologist, these areas will definitely need to be scouted for wheat midge to make effective management decisions. Insecticides may be needed to reduce yield losses from economic populations of wheat midge.

Although the forecast is good for wheat growers to avoid the ravages of wheat midge, the bad news for 2021 is that the beneficial parasitic wasp is at a historic record low, with only 1.5% of the wheat midge cocoons parasitized.

Parasitic wasps play an important role in natural control of wheat midge and parasitize the egg or larva,” she adds. “In contrast, the parasitism rate was 15% in 2020, 36% in 2019 and 9% in 2018. Parasitism was only observed in Williams, Mountrail and Ward counties.

Some tips for monitoring for wheat midge include scouting during the night, when wheat midge is most active, warm night temperatures about 59 F and winds less than 6 mph. Wheat is most susceptible to midge infestations from heading to early flowering (less than 50% flowering).

Lots of mosquito repellent and a flashlight are needed to effectively count the number of orange-colored flies per wheat head.

The economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

The dramatic decrease in wheat midge populations from 2019 is probably due to dryness in 2020, especially in August. Larvae are susceptible to dryness and require rain to emerge from the soil in late June through mid-July, and to drop out of the mature wheat heads and dig into the soil to overwinter as cocoons. Plotting precipitation from May through August against wheat midge cocoons for each surveyed county over the past 10 years shows a strong positive correlation between precipitation and wheat midge populations.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Wet Weather Increases Risk for Wheat Midge in 2020

Soil samples in North Dakota indicated increasing levels of overwintering wheat midge larvae (cocoons) for the 2020 season.

A total of 1,900 soil samples was collected from 20 counties in the fall of 2019 to estimate the statewide risk for wheat midge in the 2020 field season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

About 1% of the soil samples had very high population densities of wheat midge (greater than 800 midge larvae per square meter). The hot spots were located in west central Wells County and southwestern Ramsey County.

Another 2% was at a high-risk level (501 to 800 midge larvae per square meter) in northeastern Bottineau County, central Mountrail County and northeastern McLean County.

These populations are high and indicate that an insecticide will probably be needed to reduce potential yield loss from wheat midge, assuming wheat is in the susceptible growth stages during midge emergence and midge populations are at economic threshold levels during field scouting.

Scouting for wheat midge adults during emergence is a good integrated pest management, especially if wheat fields are in the susceptible crop stage, heading to early flowering (less than 50% flowering). Scouting for the orange adult flies is conducted at night when temperatures are greater than 59 F and the winds are less than 6 mph.

Use a flashlight and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

The moderate risk level (201 to 500 midge larvae per square meter) also was observed in 5% of the samples. Moderate risk areas were scattered in eight counties throughout the state, including the northeastern area (Nelson County), the central area (Sheridan and Wells counties), the north-central area (McHenry and Rolette counties), and the northwestern area (Divide, Mountrail, Williams counties).

These population levels are considered non-economic for wheat midge.

Thirty-four percent of the soil samples were at low risk, but scouting for wheat midge always is a good idea. The majority of the soil samples, 58%, had zero wheat midge cocoons, compared with the record low of 84% in 2018.

According to Janet Knodel, North Dakota State University Extension entomologist, this dramatic increase in wheat midge populations is probably due to the rain in 2019. Plotting out the total rainfall from May through September and total number of wheat midge cocoons for the past eight years showed a strong correlation between precipitation and wheat midge populations.

Larvae are susceptible to dryness and require rain to emerge from the soil in late June through mid-July, and to drop out of the wheat heads and dig into the soil to overwinter as cocoons.

In 2019, the beneficial parasitic wasp, which naturally controls wheat midge eggs and larvae, increased to 15% of wheat midge cocoons parasitized, compared with only 9% in 2018. The average parasitism rate was also higher: 36% in 2019, compared with less than a 5% parasitism rate for the last four years (2015 to 2018). The highest parasitism rates were found in Bottineau, Cavalier and Williams counties.

To conserve parasitic wasp populations, producers should scout for wheat midge and spray insecticides only when wheat midge populations are at economic threshold levels. Parasitic wasps fly later than wheat midge, so avoiding any late insecticide applications also will reduce the negative impacts on these ‘good’ insects. This tiny, metallic wasp does an excellent job keeping the wheat midge in check by providing free biological control of wheat midge in wheat fields.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Drought Reduces Wheat Midge Populations for the Second Year in a Row

Wheat midge likely will be less of problem this year, reducing the need for insecticide applications.

Soil samples in North Dakota indicate low levels of overwintering wheat midge larvae (cocoons) for the 2018 season, according to Janet Knodel, North Dakota State University Extension entomologist.

A total of 2,000 soil samples were collected from 21 counties in the fall of 2018 to estimate the regional risk for wheat midge in the 2019 field season. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

Less than one percent of the soil samples had economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year. The hot spot was located in one soil sample in the central area of both Burke and Ward counties in North Dakota. The majority of the soil samples, 84 percent, had zero wheat midge cocoons, which is a new record low for the wheat midge larval survey since it has been conducted in 1995.

Wheat midge populations ranged from zero to 607 larvae per square meter, with an average of 17 larvae per square meter in 2018. Wheat midge populations were slightly higher in 2017 and 2016, ranging from zero to 1,321 in 2017 and 2,071 larvae per square meter in 2016.

Other areas with low wheat midge populations (200 to 500 larvae per square meter) occurred in one small pocket in west-central Ward County. These population levels are still considered noneconomic and low risk for wheat midge.

Janet Knodel, North Dakota State University Extension entomologist, believes that the drought in the northwestern and north-central areas of North Dakota caused high mortality to wheat midge for the last two years. Larvae are susceptible to dryness and require dew or rain to drop out of the wheat heads and dig into the soil to overwinter as cocoons.

In 2018, the beneficial parasitic wasp, Macroglenes penetrans, which naturally controls wheat midge eggs and larvae, continues to be at record lows with only a 4.8 percent parasitism rate in 2018. The parasitism rate has been low since 2015 - 4.2 percent in 2017, 4.8 percent in 2016 and 3.7 percent in 2015. Ninety-one percent of the larval cocoons had zero incidence of parasitism in 2018.

The highest parasitism rates were observed in Divide, McLean and Nelson counties. Because the parasitic wasp is dependent on its host, wheat midge, its populations decreased as midge populations also decreased during the past few years.

To conserve parasitic wasp populations, producers should scout for wheat midge and spray insecticides only when wheat midge populations are at economic threshold levels. Parasitic wasps fly later than wheat midge, so avoiding any late insecticide applications also will reduce the negative impacts on these ‘good’ insects. This tiny, metallic wasp does an excellent job keeping the wheat midge in check by providing free biological control of wheat midge in wheat fields.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

Scouting for the orange adult flies should be conducted at night when temperatures are greater than 59 F and the winds are less than 6 mph. Use a flashlight and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

2018 Wheat Midge Forecast - Lowest on Record

Soil samples in North Dakota indicate low levels of overwintering wheat midge larvae (cocoons) for the 2018 season.

A total of 201 soil samples were collected from 21 counties in the fall of 2017 to estimate the regional risk for wheat midge in 2018. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

Less than 1 percent of the soil samples had economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year. The hot spot was located in one soil sample in northeastern Rolette County in north-central North Dakota. The majority of the soil samples, 75 percent, had zero wheat midge cocoons, which is a record low for the wheat midge larval survey since its inception in 1995.

Wheat midge populations ranged from zero to 1,321 midge larvae per square meter, with an average of 24 larvae per square meter in 2017. In 2016, wheat midge populations were slightly higher than 2017, ranging from zero to 2,071 midge larvae per square meter, with an average of 42 larvae per square meter.

Other areas with low wheat midge populations (200 to 500 larvae per square meter) occurred in small, localized areas in northeastern Eddy and Wells, and south-central Ramsey counties,” says Knodel. “These population levels are still considered noneconomic and low risk for wheat midge.

Janet Knodel, North Dakota State University Extension Service entomologist. believes that the dry weather in the northwestern and north-central areas of North Dakota was extremely detrimental to wheat midge in 2017. Larvae are susceptible to dryness and require dew or rain to drop out of the wheat heads and dig into the soil to overwinter as cocoons.

In 2017, the beneficial parasitic wasp, Macroglenes penetrans, which naturally controls wheat midge eggs and larvae, continues to be at record lows, with only a 4.2 percent parasitism rate in 2017, 4.8 percent parasitism rate in 2016 and 3.7 percent parasitism rate in 2015. Ninety-two percent of the larval cocoons had zero incidence of parasitism in 2017, and was similar to the levels in 2016 and 2015, with 89 percent and 91 percent, respectively.

The highest parasitism rates were found in Bottineau, McLean and Wells counties. Because the parasitic wasp is dependent on its host, wheat midge, its populations decreased as midge populations also decreased in the past few years.

To conserve parasitic wasp populations, producers should scout for wheat midge and spray insecticides only when wheat midge populations are at economic threshold levels. Parasitic wasps fly later than wheat midge, so avoiding any late insecticide applications also will reduce the negative impacts on these ‘good’ insects. This tiny, metallic wasp does an excellent job keeping the wheat midge in check by providing free biological control of wheat midge in wheat fields.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

Scouting for the orange adult flies should be conducted at night when temperatures are greater than 59 F and the winds are less than 6 mph. Use a flashlight and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Two Hot Spots for N.D. Wheat Midge Populations in 2017

Soil samples in North Dakota indicate low levels of overwintering wheat midge larvae (cocoons) for the 2017 season, according to Janet Knodel, North Dakota State University Extension Service entomologist.

A total of 201 soil samples were collected from 21 counties in the fall of 2016 to estimate the regional risk for wheat midge in 2017. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

Only two percent of the soil samples had economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year,” Knodel says. “These higher populations were located in east central Divide and southeast Burke counties in northwest North Dakota. Fortunately, the majority of the soil samples, 68 percent, had zero wheat midge cocoons.

Wheat midge populations ranged from zero to 2,071 midge larvae per square meter, with an average of 42 larvae per square meter in 2016. In 2015, wheat midge populations were slightly lower, ranging from zero to 429 midge larvae per square meter, with an average of 25 larvae per square meter.

Other areas with low wheat midge populations (200 to 500 larvae per square meter) occurred in small, localized areas in northeast Bottineau, southeast Burke, central Divide, central McLean, northeast Mountrail, northwest Renville, northwest Towner and central Ward counties. These population levels are still considered non-economic and low risk for wheat midge.

In 2016, the beneficial parasitic wasp, Macroglenes penetrans, which kills wheat midge eggs and larvae, also was low with an average of 4.8 percent parasitism rate in 2016. Eighty-nine percent of the larval cocoons had zero incidence of parasitism in 2016, similar to the level in 2015 with 91 percent.

The highest parasitism rates were found in Burke, Bottineau and McLean counties. Since the parasitic wasp is dependent on its host, wheat midge, its populations are usually higher in areas where midge populations also have been high the past year.

To conserve parasitic wasp populations, producers should scout for wheat midge and spray insecticides only when wheat midge populations are at economic threshold levels. Parasitic wasps fly later than wheat midge, so avoiding any late insecticide applications also will reduce the negative impacts on these ‘good’ insects. This tiny, metallic wasp does an excellent job keeping the wheat midge in check by providing free biological control of wheat midge in wheat fields.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

Scouting for the orange adult flies should be conducted at night when temperatures are greater than 59 F and the winds are less than 6 mph. Use a flashlight and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Record Low N.D. Wheat Midge Populations Predicted for 2016

Soil samples in North Dakota indicate decreased levels of overwintering wheat midge larvae (cocoons) for the 2016 season, according to Janet Knodel, North Dakota State University Extension Service entomologist.

A total of 183 soil samples were collected from 20 counties in the fall of 2015 to estimate the regional risk for wheat midge in 2016. The distribution of wheat midge is based on unparasitized cocoons found in the soil samples.

No soil samples were found with economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year. 74 percent of the soil samples had zero wheat midge cocoons. This is the lowest population of wheat midge ever recorded since we have been conducting the wheat midge larval soil survey, which started in 1995.

Wheat midge populations decreased by more than half from last year and ranged from zero to 429 midge larvae per square meter, with an average of 25 larvae per square meter in 2015. In 2014, wheat midge populations were higher, ranging from zero to 1,500 midge larvae per square meter, with an average of 61 larvae per square meter. In 2013, wheat midge populations were higher yet and ranged from zero to 3,285 midge larvae per square meter, with an average of 140 larvae per square meter.

The highest wheat midge numbers ranged from 200 to 500 larvae per square meter in small, localized areas in southeast Burke, northwest Divide, north central Renville, west central Sheridan and northeast Ward counties. These population levels are still considered non-economic and low risk for wheat midge.

Wheat midge populations have declined sharply for several reasons, including multiple field reports of area wide insecticide-fungicide spraying for control of wheat midge and scab disease to minimize wheat losses, and the dry conditions when larvae dropped out of wheat heads in August, causing increased mortality.

The parasitic wasp Macroglenes penetrans, which kills wheat midge eggs and larvae, also has decreased considerably from a 3.7 percent parasitism rate in 2015 to an 11 percent parasitism rate in 2014. Ninety-one percent of the larval cocoons had zero incidence of parasitism in 2015, compared with 73 percent in 2014.

“This is because the parasitic wasp populations are dependent on their host populations, the wheat midge,” Knodel says. “So, when wheat midge declines, so does  the parasitic wasp. This wasp plays an important role in keeping wheat midge controlled naturally.”

Parasitism rates ranged from zero to 100 percent across the state, with the higher rates occurring in areas where midge populations have been high during the past few years, such as Burke and Divide counties.

To conserve parasitic wasp populations, producers should scout for wheat midge and spray insecticides only when wheat midge populations are at economic threshold levels. Parasitic wasps fly later than wheat midge, so avoiding any late insecticide applications also will reduce the negative impacts on these ‘good’ insects. This tiny, metallic wasp does an excellent job keeping the wheat midge in check by providing free biological control of wheat midge in wheat fields.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

Scouting for the orange adult flies should be conducted at night when temperatures are greater than 59 F and the winds are less than 6 mph. Use a flashlight and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

Wheat Midge Populations Lower in 2015 Than 2014

Soil samples in North Dakota indicate decreased levels of overwintering wheat midge larvae (cocoons) for the 2015 season, according to Janet Knodel, North Dakota State University Extension Service entomologist.

A total of 196 soil samples were collected from 21 counties in the fall of 2014 to estimate the regional risk for wheat midge. The distribution of wheat midge in 2015 is based on unparasitized cocoons found in the soil samples.

Only 7 percent of soil samples statewide are moderate to high risk for wheat midge infestation in contrast to 21 percent last year. These ‘hot’ spots will need to be scouted to determine if fields are above economic thresholds and warrant an insecticide treatment for controlling wheat midge in 2015. Overall, most of the state is at low risk for wheat midge, which will reduce input costs, such as insecticides for wheat production.

The high-risk pocket of 800 to greater than 1,200 midge larvae per square meter are concentrated in the northwestern area of North Dakota in Mountrail and Divide Counties, she adds. Areas with moderate risk of 501 to 800 midge larvae per square meter are only in Williams County.

Wheat midge populations decreased by more than half from last year and ranged from zero to 1,500 midge larvae per square meter, with an average of 61 larvae per square meter in 2014. In 2013, wheat midge populations ranged from zero to 3,285 midge larvae per square meter, with an average of 140 larvae per square meter.

In the remaining counties, 44 percent of the samples had one to 500 larvae per square meter (low risk) and 55 percent had zero larvae per square meter.

In 2014, the parasitic wasp Macroglenes penetrans, which kills wheat midge larvae, has increased slightly to 11 percent parasitism from 7.6 percent in 2013.

"Although the parasitic wasp and wheat midge populations are cyclic, wasps play an important role in keeping wheat midge controlled naturally,” Knodel says.

Parasitism rates ranged from zero to 100 percent across the state, with the higher rates occurring in areas where midge populations have been high during the past few years, such as Burke, Divide and Williams Counties. Seventy-three percent of the larval cocoons had zero parasitism in 2014.

To conserve parasitic wasp populations, producers should scout for wheat midge and spray insecticides only when wheat midge populations are at economic threshold levels. Parasitic wasps fly later than wheat midge, so avoiding any late insecticide applications also will reduce the negative impacts on these ‘good’ insects. This tiny, metallic wasp does an excellent job keeping the wheat midge in check by providing free biological control of wheat midge in wheat fields.

Producers should use the North Dakota Agricultural Weather Network (NDAWN) Wheat Midge Degree-day Model to predict the emergence of wheat midge, determine when to scout, and see if their wheat crop is at risk.

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether the crop is susceptible to midge infestation, as well as the timing of wheat midge emergence.

Scouting for the orange adult flies should be conducted at night when temperatures are greater than 59 F and the winds are less than 6 mph. Use a flashlight and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

If wheat midge is detected, the economic thresholds for wheat midge are one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.