FROM AROUND THE STATE
ISSUE 14 August 5, 2004
BANDED SUNFLOWER MOTHS ACTIVE
Pheromone traps for adult Banded sunflower moth have been high (>500 moths per trap week) this past week in the north central region. Trap catches of male moths are accurate in determining emergence and approximate egg laying activity of adults. Adult moths are ľ inch long with a Ĺ inch wing span with a brown triangular area on forewing and light gray brown hind wings without markings. Adults can be found in grassy field margins, shelterbelts, and other areas outside of sunflower fields and move into the field at night to lay eggs. Many sunflower fields are in the proper window for egg laying, early bud to post-bloom stages. Females prefer to lay eggs on the pre-bloom to bloom stages. Eggs are laid on the bracts of sunflower, and hatch into larvae in 5-8 days. Larvae are <Ĺ inch mature and have a brown head capsule. Larvae change in color as they grow from light pink or yellow, then to reddish or purplish, and finally to green at maturity. Newly hatched larvae feed on the bracts and disk flowers where they feed on pollen. Later larvae tunnel through the disk flowers and feed on young developing seeds. As seeds mature and harden, larvae chew into the seed to feed. Each larvae penetrates and consumes the contents of 6-7 seeds. Larvae can be found from July to September with peak densities in mid-August.
When mature, larvae drop to the ground to spin silken cocoons in the soil where they pass the winter. The economic threshold is 1 adult per 2 plants. Since adults tend to congregate in field margins prior to flowering, insecticide applications to margins and field edges can reduce overall adult populations. Insecticide treatments that are directed at larvae in sunflower head need to be properly timed to get maximum control. Research has shown that the best time to treat for larvae is early pollen shed. At this time, the larvae are beginning to feed on the disk flowers, and exposed to insecticides on the head. Insecticides should be applied early in the morning or late in the day to minimize the adverse effect of pesticide poisoning on bees and other pollinators.
EUROPEAN CORN BORER IN CORN
Eggs and early instar larvae of European corn borer can be found in corn fields. Consult the Field Crop Insect Management Guide for scouting, economic threshold and insecticide information.
Janet J. Knodel
Area Extension Specialist Crop Protection
North Central Research and Extension Center
During the past week (July 28 to August 3), the south-central regionís rainfall ranged from 0.01 inches at Fingal and Jamestown to 1.25 inches at Oakes as recorded at NDAWN (North Dakota Agricultural Weather Network) sites. Most of the region received 0.25 inches or less of rain. The regionís estimated crop daily water use on August 3 for corn (May 15 emergence), soybean (May 29 emergence) and sunflower (June 5 emergence) ranged from 0.12 to 0.25 inches.
Winter wheat, spring and barley harvest is in progress in southern counties. Limited yield reports from Dickey and Ransom Counties indicate 70 to 100 bushel winter wheat and 55 to 65 bushel/acre spring wheat. In counties north of I94, small grain harvest generally will start during the week of August 8. Harvest preparation includes swathing and pre-harvest applications of glyphosate on wheat.
Most of the regionís corn is in the tasseling- to silking-growth stages and continues to be lagging in development. As of August 3 at Carrington, we were behind about 240 corn growing degree units compared to the long-term average during May 1 through August 3. With at least 50 days required from silking to physiological maturity, a late September frost is needed to achieve adequate grain yield, test weight, and seed moisture. Soybean currently is in the full flower to pod growth stages (R2-R4). Sunflower is beginning to bloom. Additional rainfall currently is needed across the region to maintain the yield potential of our row crops that are in the critical reproductive stages, while dry weather is desirable for the cool-season crop harvest.
Leaf-spot diseases will apparently have more impact on yield and quality reduction in wheat compared to scab. Septoria brown spot and bacterial blight are commonly found in soybean. During a survey the past week in Eddy, Foster, Stutsman, LaMoure, and Dickey counties, 1 of 26 soybean fields contained a soybean aphid. Growers should continue monitoring for the aphid through the R4-R5 soybean growth stages.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center