The northeastern part of the state, where we happen to also grow wheat (armyworms love wheat) in some areas, is particularly thick with migrant moths. The female moths that arrive will be loaded with eggs and looking for suitable hosts to lay them on – many plants will do the job, with grasses strongly preferred. If you have wheat acreage, or your soon-to-be-corn acres have a grass cover crop, particularly cereal rye, those fields will be an armyworm magnet. Depending on when that cover crop is killed and corn is planted, the crop could be at risk.
The level of risk depends on two main factors: 1) the level of armyworm pressure in the area (see Table below - this will be high in much of the state this year), and 2) the degree of overlap between the grass host and emerging corn. That might also be high this year. As stated last week, a period without green, growing material will readily starve most armyworms. When that’s not possible, it’s time to reach for the insecticides to hit the larvae before they can feed on emerging corn. There are many insecticide options Corn Insect Control Recommendations - E-219, but all will work best when larvae are small (less than 1¼”in length).
Scouting fields beginning late next week is advised… before then, the larvae will be too small to see easily. By early May, larvae should be quite conspicuous and scouting will be relatively easy. A sweep net can be used, or even just visually inspecting plants for damage and/or feeding larvae will work. Disturbing and poking through the top layer of soil will reveal the larvae during sunny days, when they often rest here. Although there is not a threshold for armyworm in cover crops, 4 larvae/sq. ft is the guideline in wheat. Remember, Bt corn and seed treatments won’t save you from this one. So venture out late next week and check those high-risk fields. BY CHRISTIAN KRUKPE.
No comments:
Post a Comment