FROM AROUND THE STATE
ISSUE 8 June 21, 2001
The second flight of adult Diamondback moths (DBM) is on! In North Dakota, three flights (or generations) of DBM are common. Adult moths can easily be observed fluttering about the canola at dusk. Adults are small and narrow about ˝ inch, and greyish in color with a diamond-like pattern on the forewing margins when folded together. Adult moths continue to live for 16 days. Each female adult will lay about 160 eggs that will hatch into larvae in 5-6 days. Larval will feed for about 21 days. The feeding damage on the flowers can hurt canola yields, and delay plant maturity causing uneven crop development. If you are in the "DBM hotspot" from McLean County north to Burke County, check your fields for larvae feeding on the flower buds during the next several weeks. The action threshold for an insecticide application is 1-2 larvae per plant during early flowering or 2-3 larvae per plant during podding. Capture 2EC is registered for DBM control at the 2.1 fl. oz./A. It is interesting to note that there has been no reports of DBMs in fields that were sprayed earlier with Capture 2 EC (1.3 fl. oz./A) for flea beetle control.
Bertha armyworm has emerged in the Northwest and North Central Regions. The trap counts were high, over 100 moths per week, in Renville County near Mohall and in Ward County at Minot. This is unusually high for mid June. Scout canola fields in about a week for larvae. Newly hatched larvae are small (1/10 inch), pale green with a yellowish stripe along each side. Larvae take approximately six weeks to complete their development, depending on temperature. Mature larvae are 1.5 inches long and may vary in color from green to brown or velvety black with a yellowish stripe along each side and a light brown head. Bertha Armyworms prefer canola, mustard, alfalfa as host plants, but will also feed on secondary hosts like flax, peas, and potato.
Many reports on Thistle caterpillar (larvae of the Painted Lady Butterfly) have been reported on canola, sunflower, and small grains from the North Central and Northwest Regions. Remember, it prefers to feed on thistle plants, but may move over to your crops after devouring the thistle. Some reports include large numbers of thistle caterpillars moving along roadways and ditches in search of thistles.
Apothecia, the fruiting bodies of sclerotinia, were found in last year’s canola fields in Pierce and Bottineau Counties. These fruiting bodies release ascospores that can be windborne for several miles. Remember, wet weather 10-14 days before flowering and at flowering, and temperatures in the 70NF favor sclerotinia infection.
Sunflower beetle eggs are easy to find now and should hatch into larvae in about one week. Larvae will feed in fields for about six weeks. Continue to monitor fields for economic levels of adults and/or larvae.
Aphids were observed this week in the Small Grain IPM Survey, but at very low levels.
Janet J. Knodel
Area Extension Specialist Crop Protection
North Central Research and Extension Center
During the past week (June 13 to 19), rainfall recorded at NDAWN sites in south-central North Dakota ranged from 0.6 inches (Robinson) to 2.5 inches (Carrington). The region has moisture-saturated soils. Rainfall occurred on 12 of 19 days during June 1-19 at Carrington, fortunately the highest daily rainfall amount did not exceed 0.75 inches.
Grain crop seeding is essentially complete. Annual forage crops may be seeded if soil conditions allow the work. Cool-season crop stands generally are excellent. Based on growing degree day units, wheat emerged on May 1 was in the flag leaf to awns emerging stages and wheat emerged on May 15 was in the jointing to flag leaf emerging stages, as of June 19. Canola is in the bolting to early flower growth stages. Warmer air temperatures are needed to promote growth of corn, beans, and sunflower.
Tan spot is present in most wheat fields. According to the NDSU small grain disease forecasting model, conditions favorable for tan spot were present everyday from June 8-19 at Carrington. Forecasting models can be viewed at the following website:
Net blotch is present in area barley fields. Barley yellow dwarf virus was detected in two barley fields during June 13-14 in Barnes and Logan Counties. Downy mildew can be found in sunflower. Canola growers should be monitoring the growth stage of their crop and consider use of the ND sclerotinia risk forecast map to assist with determining the need for fungicide application as canola enters the early flowering stage. Scattered reports of cutworm in row crops and diamondback moth larvae in canola have been received. Favorable weather conditions are needed to complete POST herbicide application in small grain, and to start or continue herbicide application in flax and warm-season crops.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center