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Sunflower Midge in the Southern Red River Valley
The midge is a small fly, 3/32 inch in length, that is tan colored. The midge emerges in early July. They prefer to lay eggs on developing buds, 1 to 2 inches in diameter. The cream to yellowish-orange larvae feed on bract tissue at first and later on the flowers and seeds. When feeding is confined to the bracts, damage results in little economic loss. When many larvae feed in the center of the bud, seed is not produced. This type of injury appears as twisted and gnarled flowers. Often, infestations will be limited to field margins. When populations are large, damage may extend into the field and significant field losses may be observed. Historically, infestations and losses have increased with increased sunflower production. Also, environmental conditions contribute to midge outbreaks. Good soil moisture in the month of June promotes survival and emergence of midge.
In 1995 and 1996, field scouting at the end of July, revealed significant infestations of flower heads by the Sunflower Midge. Field observations and many reports indicate fields in the southern end of the valley, west to Valley City, and east to Detroit Lakes in Minnesota had been infested by midge larvae at levels comparable to the infestations observed during the early '80's. Infestations in many of these fields were not confined to field margins. These inspections revealed many maggots per flower head, scarred bracts, and in many cases twisted or gnarled flowers. The cream-colored maggots could be found at the base of the bracts or feeding in the flower at the base of the florets.
Unfortunately, the use of conventional insecticides to control sunflower midge have not been successful. Both foliar and systemic insecticides have been used in attempts to control midge. Neither have given consistent, adequate control of adults or larvae. Multiple applications have also proven inadequate and not economical. Larvae crawl into the bud soon after hatching and are protected from topically applied insecticides.
The most promising management strategy is the use of resistant hybrids. A screening program to evaluate hybrids for resistance will continue. For the results of hybrid evaluations, refer to Extension circular A-652 to order consult http://www.ext.nodak.edu/extpubs/rowcrops.htm, or for more information on ND Hybrid Sunflower Performance Testing or Research Center data at http://www.ag.ndsu.nodak.edu/langdon/
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