ISSUE 9 June 29, 2000
ARMYWORM REPORTS CONTINUE
Additional reports of armyworm infestations are coming in from the region. Most recently, Ian MacRae, entomologist with U of Minnesota, is reporting spotty infestations in NW Minnesota.
Armyworms do not overwinter in the region, our populations arise
from adults blown in on southerly storm fronts in late spring and early summer. The
earlier the growing season, the earlier it is necessary to scout armyworms. These insects
are dark green to light brown and have a light stripe down the center of their back.
Adults lay eggs in grassy or weedy areas or in lodged grain. Armyworms, like some
cutworms, tend to feed at night and hide throughout the day. If feeding damage is found in
the foliage and no other responsible insects pest can be found, scout for armyworms by
parting foliage on the plant and inspecting the plant and the soil below for small fecal
pellets. If pellets are found (or if no other causative agent for plant damage can be
found) then look for larvae under plant trash, soil clods, or in soil cracks. If 4 to 5
worms or more are found per sq. foot,
treatment is recommended.
Refer to the previous issue for insecticide recommendations. One note regarding Warrior T insecticide and Folicur fungicide. In the event someone is considering treating wheat with this combination, it is not recommended. There are compatibility problems with these formulations.
WHEAT MIDGE UPDATE
Degree day accumulations are at the point where midge emergence is getting underway throughout the central and eastern counties. In northwest ND, counties of Divide and Burke, where populations are very large, emergence is just around the corner.
Estimated Wheat midge Emergence
Dates for North Dakota, 2000.
Field scouting of heading wheat fields that are not yet flowering will be critical during the next three weeks. Due to the smaller population of midge overwintering in the region, it will be a greater challenge to locate fields that may have treatable numbers of midge at 1 midge per 5 wheat heads.
The exception will be Divide and Burke counties. The very large population in that area should be monitored carefully. There should be treating in that area of the state.
Lorsban 4E-SG is the insecticide we have the most experience with, and it continues to work well when timed properly at 75% head emergence to early flowering. In addition, Elf-Atochem has issued a supplemental label for Penncap-M (microencapsulated methyl parathion) for the control of wheat midge. The recommended rate is 2 to 3 pints per acre. Keep in mind that there is a posting requirement in North Dakota when using any insecticide that contains methyl parathion.
CEREAL APHID UPDATE
As reported in previous weeks, aphids are in our small grain fields,
but the populations are generally tolerable. While checking some fields, I was seeing a
few more Bird Cherry Oat aphid. These fields were in Cass County, where much of the wheat
has headed and well into flowering. This late in the development of the plant, Barley
Yellow Dwarf should not be a
significant issue. Later planted fields should still be monitored for aphids. Aphids in the older fields will move soon, migrating to fields that will still be green.
EUROPEAN CORN BORER UPDATE
The blacklight trapping network is up and running. Captures of ECB moths is very low across the region. Most traps are catching zero moths, a few such as Barney, ND are catching 1 to 3 moths per night. This isnt a lot to get excited about.
In emergence cages, we are getting some moths coming out, but we are still 7 to 10 days away from an anticipated flush of emergence.
TIME TO SCOUT SUNFLOWERS FOR SPOTTED STEM WEEVIL
The Spotted stem weevil population has been small in North Dakota for the past several seasons. One report of seeing some stem weevil in the LaMoure, ND area. We had some reports of stem weevil from the Dickinson, ND area last year. Spotted stem weevil larvae cause stalk breakage when 25 to 30 larvae are present in a stalk, weakening it when larvae make their overwintering cells in the stalk's base. Breakage is most likely to occur during high winds.
The spotted sunflower stem weevil is 3/16 inches in length, and grayish-brown with varying shaped white spots on the wing covers. The weevils emerge in mid to late June. Eggs are deposited in epidermal tissue of the stem. If controls are directed at the adults in order to minimize egg laying, treatments should be initiated during the first few days in July. About 50% of the eggs are deposited by this weevil by mid July.
Treatment for sunflower stem weevils is recommended when scouting determines that an average of 1 adult per three plants is found.
Products registered for adult stem weevil control include Asana XL, Baythroid, Scout X-tra, Warrior, carbaryl, Furadan 4F and Lorsban 4E.