FROM AROUND THE STATE
ISSUE 13 July 26, 2001
WHEAT MIDGE UPDATE – NORTH CENTRAL AND NORTHWEST
The adult wheat midge activity continues especially in the Northwest Region and more northern counties. Divide County reports county-wide spraying and spotty spraying near Mohall. As the total Degree Days pass 2000, adult activity should begin to diminish. However, the moist and humid weather conditions this past week may have prolonged flight activity in some areas like Newtown. Larvae can be found feeding in the heads now.
The degree days for weather sites located in the northwest and north central regions as of July 24, 2001 include: Rolla = 1867; Bottineau = 1966; Mohall = 1962; Hofflund = 2019; Baker = 2059; Cando = 2062; Turtle Lake = 2096; Minot = 2081; Watford City = 2142; Williston = 2163; and Towner = 2218.
Continue to Scout Fields in the heading to early flower stages for damaging levels, especially in the Northwest.
WHAT ARE THE CREAM -COLORED COCOONS IN THE WHEAT AWNS?
These are cocoons of a parasitic wasp (Braconidae), which feed on many different species of caterpillars as hosts. So, enjoy these beneficial insects!
ARMYWORM AND ARCTIID (TIGER MOTH) CATERPILLARS
These are being found in small grains, forages, and soybean fields at damaging levels in North Central Region (McLean, McHenry Counties reported). Spotty infestations.
WHERE IS MY ALFALFA BLOOM? ALFALFA WEEVIL IS THE CULPRIT!
The larvae and adult feed on the foliage causing yield loss and reduced crop quality. Leaf loss greatly reduces the protein content and digestibility of the harvested crop. Unfortunately, most fields were discovered too late for control actions. Fields should be scouted when alfalfa is 6 inches high, usually mid-late May. An economic threshold is reached if 30% of the plants show feeding damage and larvae are still present. Some carryover effects from weevils feeding on the first cutting is reduced yield of the second cutting. Now, larvae have moved to the crown of the plant to pupate (non-feeding stage). Newly emerged adults will emerge in about 10 days from the pupae and may feed for a short time, but feeding damage is minimal. Adults will enter a "summer hibernation" and become inactive during the rest of the summer. This generation of adults will overwinter and serve as the source of infestation the following year.
LEAF DEFOLIATION AND WEBBING FROM WORMS IN SUNFLOWER / SOYBEANS?
THISTLE CATERPILLAR (larvae of the Painted Lady Butterfly) and the ALFALFA WEBWORM are easy to find forming webs in the leaves of sunflower and soybean. These pests continue to be damaging in SUNFLOWER AND SOYBEAN fields in the North Central and Northwest Regions. Numerous fields are being sprayed. Two unusual host reports for the thistle caterpillar include alfalfa and durum! The ALFALFA WEBWORM is 1 inch long, greenish-black with light lateral stripes, and has the unusual habit of quickly moving backwards when prodded in the front and vice versa. For identification pictures, check out the website below:
SUNFLOWER INSECTS TO WATCH FOR!
Red Sunflower Seed Weevil, Banded Sunflower Moths, and Lygus Bug can be found near field edges and in sunflower fields, especially early planted fields close to flowering. Seed Weevils and Banded Sunflower Moths are attracting to blooming fields for the nectar. So, make plans to scout as soon as the crop begins to flower. Economic thresholds are: Seed weevils = 1 weevil per head for confections, 8-9 weevils per head for oil; 1 moth for every 2 plants; and Lygus bug - no threshold yet.
SMALL GRAINS – SCAB is starting to become visible in many fields, usually about 3 weeks after flowering. Unfortunately, some fields have had high levels of severity. Low levels of LEAF RUST is also starting to show up.
CANOLA – SCLEROTINIA, BLACKLEG, and ASTER YELLOWS is visible.
Janet J. Knodel
Area Extension Specialist Crop Protection
North Central Research and Extension Center
During the past week (July 18-24), recorded rainfall at NDAWN sites in south-central North Dakota ranged from 0.6 inches at Oakes to 2.5 inches at Carrington. Also, high winds and hail have occasionally been present in the numerous and intense thunderstorms causing lodged and damaged crops. Corn, soybean, dry bean, and sunflower have benefitted most from the recent rains. Advanced development stages and warm temperatures have increased water demands by most crops. Estimates of daily water usage from NDAWN for wheat and corn emerged May 15, soybean emerged May 26, and sunflower emerged June 5 have ranged from 0.15 to 0.25 inches on July 24.
Winter wheat and barley harvest has begun in counties along the South Dakota border. Barley fields throughout the region are turning and most spring wheat fields are in the milk to dough stages. Canola generally has completed flowering. Many corn fields are in or nearing the tasseling stage. Most bean fields are in the flower to pod development stages and scattered sunflower fields are beginning to bloom. Hay harvest continues including the second cutting of alfalfa.
Recent weather has been very favorable for small grain leaf and head disease development. For example, the NDSU small grain disease forecasting model for Carrington for wheat in the early-milk stage indicated the entire period of July 13-24 was favorable for tan spot infection and 8 of 12 days favorable for leaf rust infection. Scab (Fusarium head blight) was found at generally low levels in 17 of 24 south-central wheat fields surveyed on July 23-24. Scab can be found in the Carrington Research Extension Center small grain trials including scab fungicide trials. As of July 23, the ND canola sclerotinia risk forecast map indicates this region is generally at moderate to high risk for sclerotinia (white mold) infection. Sclerotinia is being found in canola trials at the Carrington Center. Risk of white mold in dry bean also is high due to the recent wet environment. Various larvae (e.g. thistle caterpillar, alfalfa webworm, sunflower beetle) continue to defoliate broadleaf crops.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center