NDSU Crop and Pest Report

FROM AROUND THE STATE


ISSUE 12   July 22, 2004

North-Central ND

Watch for GRASSHOPPERS in preferred crops like flax and lentils, and late seeded crops.

Any stage of grasshoppers from 1st instars (about ¼ inch) to adults can be found in the North Central and Northwest Regions of North Dakota now. This is due to the prolonged emergence period this year. Some edge spraying has already occurred in lentils, small grains, and flax. Adults will become more common as we get into August. Remember, adult grasshoppers can fly and find green fields (later crops) readily. As a result, they become more difficult to control and require a higher rate of insecticide for control and sometimes repeated applications.

Canola Insect Pests:

Trap catches for DIAMONDBACK MOTHS have increased, while BERTHA ARMYWORMS continue to be low (<20 per trap week).

High numbers of adults (>100 moths per trap week) are being captured in the traps located in Ward, McKenzie, and Williams Counties. Although trap catches are higher for diamondback moth, most of the canola crop is past the most susceptible stage (flowering), or growing quickly with the heat. This flight represents the second generation of diamondback moth. Larvae feed on the leaves, buds, flowers, seed pods, the green outer layer of the stems, and occasionally, the developing seeds. The amount of damage will depend on the crop stage and the larvae densities and size. Extensive feeding on the flowers will delay plant maturity, cause the crop to develop unevenly, and significantly reduce seed yield. Larvae of diamondback moth can be monitored for by beating or dislodging the larvae from plants. The action threshold for canola at the pod stage is about 20 per square foot (two to three larvae per plant). For the early flowering stage, insecticide applications are likely required at larval densities of 10-15 larvae per square foot (one to two larvae per plant). Early monitoring of adults and larvae and judicious use of insecticides only when fields are above thresholds are the best pest management practices for preventing losses from diamondback moth on canola. A number of natural factors can also negatively affect diamondback moth populations. For example, heavy rainfalls can drown many larvae of the first generation. Humid conditions associated with rainfall can also favor the development of fatal fungal diseases like Entomophthorales. In addition, there are several parasitic wasps and predators (flies, lacewings, minute pirate bugs, spiders and birds) that prey on the larvae of diamondback moth.

See website for trap data and locations:

http://www.ag.ndsu.nodak.edu/minot/pest/index.htm

Blister Beetles:

Blister beetles have been reported feeding on canola flowers. Several species of blister beetle feed on canola including: Lytta nuttalli, a large purplish green beetle; Epicauta fabricii or the Ash_gray blister beetle, and Epicauta ferruginea, a smaller rusty color, pubescent beetle. Most species of blister beetle have one generation a year. Adults become active in early to mid summer and lay eggs in the soil. Eggs hatch in about two weeks into larvae called triungulins, which actively prey on ground nesting grasshopper egg pods (genus Epicauta) and bee eggs (genus Lytta). Larvae overwinter. Adult blister beetles are attracted to blooming canola fields, where they are ravenous feeders devouring leaves, stems, flowers, and pods. These beetles are mobile and often congregate in certain spots in a field from their gregarious behavior. In some instances, blister beetles feed for a short period of time and then migrate to other plants or fields.

The presence of large numbers of blister beetles in spots of a canola field has often concerned growers. However, adult feeding is generally not significant enough to warrant an insecticide treatment. The "High Plains Integrated Pest Management Guide" recommends treatment when there are 10 adult blister beetles per plant feeding on the flowers or pods. However, there is no economic threshold in North Dakota. Spot treatment with foliar insecticides registered in North Dakota is usually recommended when necessary. These insecticides will control blister beetles. Follow safe pesticides practices when spraying flowering canola to protect honey bees.

WHEAT MIDGE:

Emergence is underway in the North Central and Northwest Regions of North Dakota; however, scouting and trapping reports indicate low numbers.

Fortunately, most of the night scouting and pheromone trapping reports have been below damaging levels so far. There has been some spraying with reduced rates of lorsban in conjunction with applications for scab, Fusarium head blight. Continue to monitor wheat and durum in the susceptible crop stage, heading to 50% flowering, for wheat midge activity.

Watch for APHID populations in small grains.

Increasing populations of aphids have been detected this past week. Late planted small grains should be scouted for aphid populations. The treatment threshold is 85% stems with at least one aphid present, prior to heading. The vegetative to boot stages are the most susceptible stage to aphid feeding and subsequent yield loss. After flowering, small grains are less susceptible and producers are discouraged from spraying. Natural biological control agents, like lady beetles, lacewings, often keep aphids in check later in the summer.

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

 

South-Central ND

During the past week (July 13 to 19), the south-central region’s rainfall ranged from none at numerous sites to 0.6 inches at Harvey as recorded at NDAWN (North Dakota Agricultural Weather Network) sites. The region’s estimated crop daily water use on July 19 for wheat (May 1 emergence), corn (May 15 emergence), soybean (May 29 emergence) and sunflower (June 5 emergence) was 0.09 to 0.31 inches. Water use data is available at the following NDAWN website:

http://www.ext.nodak.edu/weather/cropwater/

Additional rainfall generally is welcome, especially for the warm-season crops.

Winter wheat and barley are nearing harvest in southern counties. Yield potential of small grain, canola, field pea, and flax continues to be generally excellent. Flag leaf disease (tan spot, Septoria, and rust) incidence and severity is increasing in spring wheat. About three weeks after flowering is the prime time to check wheat for scab symptoms. Sunshine and warm weather has dramatically increased the growth rate of corn, beans and sunflower.

Corn growth stages range from 8-10 leaf. As of July 19 at Carrington, we were behind about 225 corn growing degree units (equivalent of about 2.5 leaves) compared to the long-term average for the May through two-thirds of July period. Soybean are flowering (R1-R2 stage). Grasshoppers are becoming more common, especially in the drier areas. Downy mildew was found in 9 of 14 (64%) south-central sunflower fields during last week’s IPM crop survey. Some growers are reporting significant stand losses due to the sunflower disease. Soybean root rot and defoliation by insects are being reported.

Greg Endres
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center
Gregory.Endres@ndsu.nodak.edu

 

Northeast ND

Areas in Benson and Towner counties received up to 1 inch of rain last week while the rest of the region received only traces of rain.

Cool season crops continue to look good. Earliest planted Barley and wheat are in milk while the rest is heading to flowering. Barley is filling nicely with just low levels of fusarium head blight. Trace amounts of scab starting to show in earliest wheat Earliest canola is finishing bloom while the remaining 50% of Canola acreage is blooming. Winter wheat has above average head size and kernel numbers with yield expectations similar to last year. Corn growth continues to lag behind normal expectations. Normal GDD accumulations would predict silking around Aug 7th for most corn in the region. Soybeans are around the sixth trifoliate leaf stage and in the bloom stage Volunteer canola emerged as wide scale problem in soybean and corn.. Fungicide application is continuing on small grains. Leaf rust infection on susceptible wheat is a major problem south of highway seventeen. Low levels of tan spot, septoria and rust are being found in wheat in northern areas where later planted wheat is flowering while these diseases are expanding coverage in earlier planted wheat. No major bug or disease problems evident to date.

Terry Gregoire
Area Extension Agronomist
Devils Lake Area Office
tgregoir@ndsuext.nodak.edu


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