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FROM AROUND THE STATE


ISSUE 13  JULY 29, 1999

 

North-Central ND

LATE SEASON INSECT PESTS OF CANOLA

    The pheromone trap network is being monitored for the Lepidopterous insect pests of canola:
Diamondback moth and Bertha armyworm. Thanks to the many cooperators - county extension
agents/specialists, crop consultants, growers! High trap counts generally indicate the level of larval
populations to follow. The second peak of the Diamondback moths occurred in the North Central
Region during mid-July. Fortunately, trap counts were below economic levels (<100 moths per trap
week) in most areas. The recent heavy thunderstorms washed larvae off the foliage and drowned
them! Trap counts for Bertha armyworm have increased (>200 moths per trap week) in a few
areas where they historically have been a problem like Bottineau-Renville Counties. In other areas,
trap counts are relatively low. Fortunately, no pest problems are expected on the late planted canola!

    Nuttall Blister beetle has been reported infesting canola fields near Bowbells, Sherwood, and
Devils Lake area. The blister beetle moves from freshly cut alfalfa fields in search of an alternative
food source - canola. The blister beetle clips the flowers and sometimes the terminals. Moving in
large swarms, the beetles can cause significant damage in localized areas. Spot treatment with sevin
is usually recommended for control.

    Aphids are moving into our area from the southern tier of North Dakota. Three species of aphids
attack canola: green peach aphid, turnip aphid, and cabbage aphid. The green peach aphid is
the most formidable pest because of its tolerance against the insecticides used. Aphids feed on the
terminals, and cause wilting and delayed flowering. In most cases, infestations are only spotty and
damage is not significant. There is no economical threshold, but treatment is not recommend after
flowering. There are many natural enemies which help control aphids in fields, like ladybeetles
and lacewings.

    Wheat Midge Update
    Wheat midge populations are starting to decrease in the southern part of the North Central Region
like Minot. However, in the more northern parts like Crosby to Flaxton, night visual counts are still
recording high populations (1 midge per 4-5 heads). Currently, we are at the following DDs as of
July 26, 1999: Columbus = 1732, Rolla =1832, Bottineau = 1976, Mohall = 2006, Turtle Lake =
2063, Towner = 2065, Minot = 2098, and Williston = 2113 (Source: ND Ag Weather Network).
Remember, the wheat midge will continue to live for another 7-10 days after the 1600 DD
mark (90% of emergence completed) with the warm, humid weather!

    Sunflower Beetle In Action
   Numerous fields were treated earlier in the season for sunflower beetles. However, there are still
reports of fields above the economic threshold level (10-12 larvae/plant or 25% defoliation) in
Bowbells, west of Minot, and will be sprayed. The new generation of adults is emerging! One
field near Souris had over 100 new adults/plant on some plants located near the field edge and
were completely defoliated (source: M. Hutter, Northern Ag Management).

    Fusarium head blight (wheat scab) has been detected at low levels (10% incidence) in Ward
County during the IPM Wheat Survey this past week. The small grain disease forecasting model
indicated low levels of infection during July 26th. Please see NDSU website:

http://www.ag.ndsu.nodak.edu/cropdisease/wheat/interpret.htm

Janet J. Knodel
Area Extension Specialist Crop Protection
North Central Research and Extension Center
Minot, ND

South-Central ND

    Rainfall continues to occur very frequently although sporadically over the south-central region. The
ND Ag Weather Network weather stations in this region recorded no rain at Linton to 5.35 inches at
McLeod during July 21 to 27. While soil moisture appears adequate, water use by most crops is high.
For example, daily water use measured on July 27 at the Carrington Research Extension Center was
0.13-0.29 inches for wheat and barley, 0.22-0.3 inches for corn and potatoes, 0.28 inches for alfalfa,
and 0.24-0.3 inches for dry bean. Numerous counties in the region have had hail-damaged crops in
localized areas.

    Second-cut alfalfa and grass hay harvest continues but frequent rain events, heavy dew, and high
humidity are hampering progress. Annual warm-season forages continue to be planted. Winter rye
and wheat harvest, and early-spring seeded small grain swathing has begun in southern areas of south-
central ND. Some early-seeded canola also has been swathed. Most of the area's canola crop will be
swathed in the next 1-3 weeks. Corn, soybean, dry bean, and sunflower generally are in good condition
and rapidly developing with the warm weather and adequate soil moisture.

    Wild oat, kochia, Canada thistle and other weeds are becoming more obvious in many fields.
Numerous insects and diseases currently can be found. Insect trapping at the Carrington Center
continues for the European corn borer, diamondback moth, and Bertha armyworm. Moth levels
for all three insects are currently low. Aphids, grasshoppers, and leafhoppers continue to be present
in the region and populations should be monitored. Some canola growers have expressed concern with
aphid injury. Very low levels of aster yellows, a disease transmitted by leafhoppers, can be found in
flax and canola. Sunflower growers should continue monitoring for sunflower beetle larvae and head-
damaging insects including seed weevils and sunflower moths.

    Levels of leaf-spot diseases (tan spot, rust, and septoria) are rapidly increasing in small grain fields.
Symptoms of barley yellow dwarf virus can readily be observed in many wheat fields. Scab symptoms
in wheat should be obvious about three weeks after flowering if infection occurred. Common leaf blight
has been found in corn. Leaf rust in sunflower can be found in the area. Sclerotinia is present in dry bean
(white mold) and sunflower (wilt). Downy mildew in sunflower is present but at generally low levels.

Greg Endres
Area Extension Specialist/Cropping Systems
Carrington Research Extension Center
gendres@ndsuext.nodak.edu


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