ISSUE 4 May 31, 2007
GET READY TO SCOUT FOR CEREAL APHIDS
Large populations of aphids have been reported in southern states on winter wheat and spring wheat. These aphids will be migrating into North Dakota soon. The greenbug, English grain aphid and bird cherry oat aphids are the principle species that cause problems in North Dakota small grains. These aphids transmit barley yellow dwarf virus. When aphid populations are high, the disease can spread quickly through small grain fields. At greatest risk are later planted fields which attract migrating aphids that are moving from more mature fields.
Greenbug - pale green with darker stripe down back.
Bird Cherry Oat Aphid - olive green, brownish patch at the base of cornicles (tube-like structures at posterior)
English Grain Aphid - bright green with long black cornicles.
When to Scout: Field scouting should begin at stem elongation and continue up to the heading stage of wheat.
Thresholds for Small Grain Aphids: English Grain, Bird Cherry Oat, Greenbug
To protect small grains from yield loss due to aphid feeding, three different treatment thresholds are available:
85% stems with at least one aphid present, prior to complete heading.
12-15 aphids per stem prior to complete heading
100 aphid days prior to complete heading (=0.6 bu/acre yield loss)
If you averaged 10 aphids per stem and had 12 days to reach heading, you would have 120 aphid days (10 aphids x 12 days). This is above the 100 aphid day threshold and an insecticide should be applied to prevent yield loss. On the other hand, if you averaged only one aphid per stem and had 12 days to reach heading, you would only have 12 aphids days (1 aphids x 12 days). Thus, no control action would be necessary.
Susceptible Crop Growth Stage: The crop’s growth stage also affects its susceptibility to aphids. The vegetative to boot stages are the most susceptible stage to aphid feeding and subsequent yield loss. For example, in the 4-6 leaf stage, injury caused by aphid is stunting, decreased number of kernels per head, and decreased kernel weight. In the boot stage, only kernel size and weight are affected by aphid feeding (not number of kernels per head). By heading, only kernel weight is affected. After flowering, small grains are less susceptible and producers are discouraged from spraying.
Lady beetles, aphid lions, syrphid fly, and parasitic wasps play a major role in reducing aphid populations. When natural enemies are present in large numbers, and the crop is well developed, farmers are discouraged from spraying fields.
ALFALFA WEEVIL DEVELOPMENT - DEGREE DAY (DD) UPDATE
200-300 DD - Scout soon
300-400 DD - Scout now
400-500+ DD - Scout & Treatment Decision
Adult alfalfa weevil
(photo Clemson Univ - USDA Coop. Ext. Slide Series)
UPDATE ON THE "TEMPO" ISSUE
There are several "Tempo" products registered in North Dakota (see list below) for control of insect pests on ornamentals and turf. In June 2006, the North Dakota State Department of Agriculture denied the state registration of Tempo SC Ultra Insecticide formulation with EPA Reg. No. 432-1363. The basis for the denial was the presence of unenforceable label language. However, the following "Tempo" products (active ingredient cyfluthrin) are registered and legal to use in North Dakota:
Tempo SC Ultra Insecticide with EPA Reg. No. 312-5498
Tempo SC Ultra Premise Spray
Bayer Professional Care Tempo Ultra WP Insecticide
Tempo 1% Dust Insecticide RTU
Tempo 2 Insecticide
Tempo 20 WP Golf Course Insecticide
Tempo 20 WP Insecticide
Tempo 20 WP Insecticide
Tempo 20 WP Insecticide in Packets
Tempo 20 WP Insecticide in Water Soluble Packets
Tempo 20 WP Golf Course Insecticide
Tempo Ultra GC Insecticide
Tempo Ultra WP Insecticide
Tempo Ultra WSP Insecticide
See Kelly Solutions website for specific label and EPA Registration information for the State of North Dakota:
If any dealer holds the unregistered Tempo SC Ultra Insecticide formulation with EPA Reg. No. 432-1363, they have three options:
1) Send the product back to its wholesale source.
2) Ship it to a dealership in another state, which has its legally registered.
3) Hold it until this year’s Project Safe Send collections and dispose of it there.
Remember, it is illegal to sell any pesticide in North Dakota that is not registered with the North Dakota Department of Agriculture! For more information, please contact Jim Gray at the North Dakota Department of Agriculture (1-800-242-7535).
WIREWORMS STILL ACTIVE ON WHEAT AND OTHER CROPS
Wireworms damage crops by feeding on the germinating seed or the young seedling. Damaged plants soon wilt and die, resulting in thin stands. In a heavy infestation bare spots may appear in the field and reseeding may be necessary. Crops susceptible to injury include small grains, corn, potatoes, sugar beets and vegetables. Legumes are less likely to be injured. An insecticide seed treatment may have been applied at planting for protection against wireworms; however, the efficacy of these seed treatments are usually reduced after 30 or more days after planting depending on the product. The recent cool, damp spring weather has slow plant development and prolonged the period where plants are susceptible (seedling to early plant growth stages) to wireworm feeding injury. As a result, economic damage is being reported in some areas with high wireworm pressures. Unfortunately, there is no rescue insecticide treatments available. Larvae will continue to move up and down in the soil profile in response to temperature and moisture. When soil temperatures are near 50 F, larvae feed within 6 inches of the soil surface. At the end of May, the whole state of North Dakota has soil temperatures above 50 F at 4-inch soil depth (source NDAWN). When soil temperatures become too hot (>80 F) or dry, larvae will move deeper into the soil to seek more favorable conditions and quit feeding.
(photo M. Boetel, NDSU)
SUGARBEET ROOT MAGGOT: MAJOR FLY ACTIVITY EXPECTED NEXT WEEK
Sugarbeet root maggot (SBRM) activity is on the rise in the Red River Valley. Flies were first detected on power poles in the northern portion of the Valley (Pembina County) on May 15. Moderate numbers of flies have also been observed in the Baker, MN area. Fly populations are being monitored throughout the Valley via a cooperative project between NDSU, the American Crystal Sugar Company, and the Sugarbeet Research and Education Board of MN and ND. Visit the following website to view maps of the fly counts:
Soil degree-day (DD) accumulations indicate that significant levels of SBRM emergence from old (last year’s) beet fields should occur in the next 2 to 5 days. However, it will take a few additional days before flies enter beet fields in large numbers to mate and lay eggs. According to the NDSU root maggot development model, peak fly activity in current-year beet fields is likely to throughout the Valley could occur within the next 5 to 10 days, depending on location and weather conditions. Based on current air DD accumulations and the extended forecast, the model projects the following dates for peak activity:
Table 1. Air Degree-day (DD) accumulations and peak fly activity projections for representative sites of the Red River Valley, May 29, 2007.
Fly movement into beet fields usually peaks on or shortly after the first fair-weather, 80-degree day after the accumulation of 600 DD units. Flies will not be as active during cool, windy, or rainy weather. Thus, what would have been the true peak can be delayed, and its intensity can be spread out over a few days if inclement weather persists.
Growers in all eastern ND sugarbeet-producing areas and those in most adjacent counties of MN should be aware that flare-ups in fly activity during the next 10 days could warrant treatment with a postemergence insecticide. Infestations of 1 or more flies per plant in sugarbeet fields may be economically justifiable to require a postemergence insecticide application. Vigilance in applying postemergence materials to manage the root maggot in these areas could also help curb the development of damaging populations in these areas for next year.
CONTROL OPTIONS: Postemergence granular insecticides should work well this year because most soils are moist, and the moisture helps activate the insecticide quickly.
NDSU research indicates that applying a granular insecticide early (1 to 2 weeks prior to peak fly activity) can provide excellent root maggot control. Some fields may be too wet to enter for applying granular insecticides at this time. The need for prompt action in the next few days could necessitate aerial application of a liquid insecticide formulation to protect those fields. Liquid insecticides are most effective if applied within 2-3 days of peak fly activity. A broad peak in fly activity is expected this year, so applying 2 split treatments of a liquid insecticide may be more effective. If such a program is selected, apply the first treatment 2 to 3 days before anticipated peak fly activity, and repeat the application about 5 to 7 days later.
For further guidance on anticipated populations in the region or for specific information on sugarbeet root maggot management, please refer to the "Insect Control" section of the 2007 Sugarbeet Production Guide for more detail and specific recommendations. An online version of this publication is at:
Research & Extension Entomologist