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ISSUE 1   May 6, 1999

1999 NORTH DAKOTA INSECT MANAGEMENT GUIDE AVAILABLE ON WORLD WIDE WEB

    For your reference, the insect management guide, published annually by NDSU, is available
on the internet. You can find it at the following address:

http://www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm

 

SECTION 18: WARRIOR ON CANOLA

    A section 18 was approved on March 30 for the use of Warrior Insecticide or Warrior T
Insecticide, a product of Zeneca, for use on canola to control flea beetles.

The dosage per acre is:
fl. oz. per acre 2.56 to 3.84
pounds AI/acre 0.02 to 0.03
Application can be by ground or air with the recommended volumes:
ground 10 gallons/acre
air 2 to 5 gallons/acre

A copy of the label MUST be in the possession of the user at the time of application.

 

CUTWORMS AROUND THE STATE

    One of the first insect pests we encounter in a season are cutworms. Currently, the only
reports of cutworm activity are coming from the southwest counties where army cutworm
have been feeding on winter wheat, canola and alfalfa. Reports are scattered, which means
vigilance through field scouting should occur.

    Last season, dingy cutworm were reported in eastern counties about ten days after the
first reports from the southwest.

    Of the cutworms that pose problems in North Dakota, the army cutworm and dingy
cutworms overwinter as partially grown larvae and are usually the first to cause damage.
The pale western, dark sided, and red-backed cutworms, overwinter as eggs. Many cutworm
infestations are associated with weedy, wet and reduced tillage areas. Here are brief
descriptions and notes on the habits of the key cutworms (size is for full grown larva):

Army cutworm: 1 1/2 to 2 inches; pale greenish-gray to brown with pale stripes and mottled
    pattern. Larvae hatch in fall, resume feeding in early spring. Important in western North Dakota
    grain fields. There were reports from South Dakota in late April of significant infestations by
    army cutworm in winter wheat and alfalfa.

Pale Western cutworm: 1 1/2 inches; generally gray in appearance. Larvae hatch in spring.
    They feed underground, sometimes damaging plants before they emerge; cut plants are pulled
    underground. Important in western North Dakota small grain.

Dingy cutworm: 1 1/4 inches. Dull, dingy brown color mottled with pale white spotting.
    Larvae hatch in fall, resume feeding in the spring when soils warm. Damage usually consists
    of chewed foliage and/or cut stems. Injure sugarbeet, corn, sunflower, and potatoes.

Darksided cutworm: 1 1/4 to 1 1/2 inches. Pale brown on top, lighter on the bottom. Sides
    have faint stripes. Larvae hatch in spring (mid to late May). Plant feeding same as above.

Red-backed cutworm: 1 to 1/4 inches. Dull gray to brown with dull reddish stripe down back.
    Larvae hatch in spring (mid to late May). Plant feeding same as above, same hosts.

Action Thresholds for Cutworms by Crop:
Small grain 4 to 5 cutworms per square foot
Corn 3 to 6% of plants cut and small larvae less than 3/4 inch present
Sugarbeets 4 to 5% of plants cut
Soybean/Drybean 1 or more larvae per three feet row or 20% of plants cut
Sunflower 1 per square foot or 25 to 30% of plants cut
Forage 5 or more per square foot

 

WHEAT MIDGE DEGREE DAYS

    With the favorable temperatures, degree days (DD) reached the point where wheat
now being planted is in the window of time where synchrony between wheat midge
emergence and heading occurs.

Wheat Midge Degree Days
Used as a Guideline for HRSW Risk Assessment

HRSW planted PRIOR to accumulating 200 DD will head before wheat midge emerge.

HRSW planted FROM 200 to 600 DD will be heading at the time wheat midge are emerging

HRSW planted AFTER 600 DD will head after peak emergence and should be at low risk to midge infestation (higher risk for barley yellow dwarf and frost, however)

 

    All counties with concerns about wheat midge have reached the 200+ DD mark. In the valley,
we range from 270 in the north to 330 in the south. In east central counties, we range from 220
to 250 from north to south. In the northern tier of counties, we range from 200 in the northwest
to 230 in the northeast

    A new web site with information on wheat midge is now available. This site will include links
to the North Dakota map which tabulates degree day totals daily. The site can be reached through
the address: http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/

 

ANTICIPATE SEED FEEDING INSECTS

    With recent rains, the cool, wet soils we will likely be planting into will slow seed
germination. When germination is slow, seeds are exposed to seedcorn maggots and
wireworms for an extended period of time.

    The seedcorn maggot is a yellowish-white worm about 1/4 inch long. They are a particular
problem on corn and dry beans, but may also injure potatoes, sunflowers, soybeans and others.
In North Dakota, the adult flies emerge in May. These flies are attracted to fields high in organic
matter. Fields rotated from corn, small grains or native grass are most susceptible.

    Eggs of the seedcorn maggot hatch at a 50EF soil temperature. The young maggots feed on
organic matter first, later on seeds, cotyledons and shoots. Dry beans are particularly susceptible
because the maggot can develop at temperatures below the minimum requirement for dry bean
germination (soil temperature of 55EF). Factors that delay germination and emergence of field
crops favor seedcorn maggot injury.

    Wireworms are another soil insect whose damage is more common when seed germination
is delayed by cool soil temperatures. The yellowish, slender, hard-bodied larvae range in size
from 1/4 to 1 1/4 inches long. They overwinter as larvae in the soil. When soil temperatures
are warm enough for seeds to germinate, wireworms will already be actively feeding.

    There are no insecticide rescue treatments that can be applied to stop injury from these
pests after planting. Treatment decisions must be made prior to planting. Seed or planter
box treatments with products containing lindane, diazinon, chlorpyrifos, or permethrin
provide protection against moderate infestations. Be sure to read your pesticide labels for
rate, mixing instructions, etc for different crops.

 

SUGARBEET PLANTING INSECTICIDE OPTIONS

    Sugarbeet root maggot (SBRM) population levels are expected to be similar to 1998
levels. Walsh and Pembina counties have the potential for high SBRM populations. Moderate
to high populations are also expected in Moorhead/Glyndon and Baker/Foxhome areas.
Central parts of the valley, from Hillsboro north to include the northern counties in
Minnesota, should experience moderate population levels. The southern end of the valley
should have low to moderate maggot pressure.

Red River Valley Sugarbeet Root Maggot Control Recommendations for Moderate Populations

Insecticide Pounds
AI/Acre
Pounds
Product/Acre
Counter 15G 1.5 10
Diazinon 14G 1.5 10.7
Dyfonate 15G 1.5 10
Lorsban 15G 1.5 10

 

ASANA AND SUGARBEET ROOT MAGGOT ?

    With the labeling of Asana XL for sugarbeet insect control, some questions have been raised
about its use against SBRM. This insect does not appear on the Asana XL label. Though some
adult control is expected with contact sprays, it may not be adequate during the entire window
of fly activity. Further, we would not expect soil activity from the active ingredient,
esfenvalerate. This product was evaluated for its impact on SBRM populations in 1998, but
control was poor and reliance on this product would be risky.

Treatment

Product / Acre

Yield
(T/A)

Recov. Sucrose (Lb/A)

$ Gross return/A

Pre

Post

Glyndon, Mn

Counter 15G 11.9 lbs ---- 14.98 3449 264
check ---- ---- 12.63 2683 177
Asana XL ---- 9.6 fl oz* 12.00 2651 184
LSD=     3.53 781  
St. Thomas, ND
Counter 15G 10 lbs ---- 21.30 5623 540
check ---- ---- 18.20 4853 468
Asana XL ---- 9.6 fl oz* 16.13 4342 435
LSD=     2.36 687  

* rate was applied as equal split applications at 4 day intervals during peak fly activity.

Phillip Glogoza
Extension Entomologist


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