The Roundup -

County Agent Update

Wheat Insects

 


Throughout the summer months, we are always seeing insects. Two insects to be on the lookout for when growing wheat in North Dakota are the Armyworms and Wheat Midge. Armyworms are starting to become a concern for the eastern part of North Dakota. When the armyworms are moths, they can invade a new area and their infestations can be sporadic. In fields where armyworms are present, there will be a low number of insects found. The damages are defoliated leaves which are generally only reported along field edges and in lodged areas of the fields. Mature armyworm larvae can clip heads, but it becomes more common as the crop matures. Pre-Harvest Intervals (PHI) are important and you need to follow the limits of which insecticides need to be applied for armyworm control. Malathion and Lannate, both restricted use pesticides, are the only two insecticides registered in barley and wheat. They both have a PHI of seven days, which means you need seven days after application until harvest. Armyworms are the most active at night, which means spraying in the evening would have the most control. Make sure you use enough water to get the insecticide down into the crop canopy. This information was gathered from the NDSU Crop and Pest Report, July 9th edition.

The other insect to be on the lookout for is Wheat Midge. Wheat midge, or also known as the orange wheat blossom midge, is one of the most destructive pests in the wheat crop. The adult midge is orange, fragile and very small, about half the size of a mosquito. Wheat midge only has one life cycle per year, they start to emerge from the soil late June to early July. These insects are seed eaters, they infest the plant during heading through flowering. When the eggs hatch, the larvae will crawl down into the seed and starting eating the enzymes, which will leave the kernel small and shriveled. The economic damage that occurs because of wheat midge will cause reduced yields, grain quality and germination and growth vigor of seedlings. The wheat midge adults can also act like a vector for other diseases to enter the plant such as wheat scam and glume blotch. The economic threshold levels are as followed; hard red spring wheat- one or more wheat midge for every four to five heads. Durum wheat- one or more wheat midge for every seven or eight wheat heads. It is not recommended to treat after 50% of the heads have flowered. Using a general insecticide is what is recommended, spraying at dusk is best because the wheat midge is most active at night. This information was gathered from Janet Knodel and Mangala Ganehiarachchi

Mentioned above were two insects you should look out for, but what about the good insects. One that we want to keep around is the Megarhyssa atrata, a giant black parasitic wasp, which is beneficial insect that attacks wood borers. These adult wasp are active from June through September and live for up to 27 days. The females will lay their eggs on top of wood borer insect eggs, so when they hatch, the wasp young will eat the larvae of the wood borers. Most of us do not like the wasps that we see in our flower beds, but these ones we want to keep around. They do not harm the plants, only the insects that eat them.

 

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