FROM AROUND THE STATE
ISSUE 8 June 20, 2002
CUTWORM PROBLEMS ON SUNFLOWER, SOYBEAN, CANOLA . . .
Many fields have been sprayed for cutworms on sunflowers, soybeans, and canola in the north-central Region. Some fields have been loss to cutworms and/or wireworms. Due to the late season, cutworms will continue to be a problem through June. By the end of June, most of the cutworms should be done feeding. Check your fields for cutworms/damage. Look for cut plants, wilted plants (chewed off below ground), or injury on foliage. Some species of cutworms are referred to as "Climbing cutworms." These cutworms can climb up plants and chew on the foliage causing defoliation similar to sunflower beetles and grasshoppers. Dig 1-3 inches down into soil around recently damaged plants to find cutworm larvae (worms). Remember that cutworm larvae are sometimes hard to find. The economic thresholds for cutworms in North Dakota include:
These economic thresholds assume that the crop is well established and has the desired plant population per acre. So, know what your plant population is first. If the plant population is low, the economic threshold may not apply. For example, an oil sunflower stand of 17,000 plants per acre is below the desired plant stand count of 23,000 plants per acre. In this case, the grower can not afford to lose many sunflower plants to cutworms, and the economic threshold will not apply. Low plant stand counts in sunflowers can also results in larger heads, which will take a longer time to dry down in the fall and delay harvest further on an already late planting.
For the best pest management of cutworms, time sprays to kill the small larvae (worms) <¾ inch long, and spray at night when cutworms are actively feeding.
SUNFLOWER: SUNFLOWER BEETLES
Sunflower beetles are becoming more numerous and starting to move in sunflower fields from volunteer sunflower fields. Continue to check fields for sunflower beetles, and treat fields with 1-2 adults per seedling.
SUNFLOWER: APION BLACK STEM WEEVIL
Some reports of adult black stem weevils on sunflower seedlings have caused some concern from the punctures (pits) in the cotyledons. However, high numbers of adult black stem weevils are necessary for causing damage to sunflower seedlings – usually >10 adults per seedling! Fields that are being sprayed with insecticide for cutworms or sunflower beetles will also kill the black stem weevil.
CANOLA: FLEA BEETLES
Flea beetles decreased this past week (June 10) with the cool, rainy weather. However, the trap counts in the north-central Region have increased again this week (June 17). Most of the canola is in the 4-leaf crop stage now, and should be able to out grow any further damage. However, there are a few late seeded fields that should be scouted for flea beetle damage.
HARDWOOD TREES: PRAIRIE TENT CATERPILLARS
Prairie tent caterpillars have been reported causing damage to shelterbelts and yard trees. Larvae are sparely hairy, mostly black with a white mid-dorsal stripe, and reddish-orange and bluish markings. Larvae live in colonies and construct large silk tents around the fork or branches of trees. Larvae feed outside the tent making insecticide control easy. The caterpillar’s nests are unsightly and larvae can defoliate trees. But, little permanent damage is likely to be caused. Hosts include choke cherry, and other hardwood species.
Area Extension Specialist/Crop Protection
North Central Research Extension Center
Crop growth is good in non flooded areas. Crusting is a problem especially for later seeded flax. Sunflower seems to be emerging well even in crusted areas. Poor stands of canola, flax and some pea acreage has been or will be worked down . Some sunflower, barley and flax was planted this week. Growers are assessing flood damage as water has receeded in many areas. Perhaps 5-10 percent of seeded acres were lost by growers west of the Red River Valley with individual losses being much higher in areas of the valley.
Small grains are generally in the 4-5 leaf stage, sunflower, soybean and dry beans are in the two leaf stage, canola in 3-5 leaf stage, and Flax is 1-2 inches tall. In general First bloom on canola will occur the end of June. Weed spraying in common in most crops. Many growers waited for a new flush of weeds emerging this week after the rain.
Area Extension Specialist/Cropping Systems
Counties in southwest North Dakota have experienced a great deal of variability in precipitation amounts during the past week of June 10 – 17. The greatest amount of precipitation reported on the NDAWN system was at Bowman with 1.12 inches with the least reported at the Hettinger site at 0.02 inches.
Winter wheat is now beginning to head. Hard red spring wheat, barley, and oat that were seeded in mid-April are jointing. In areas where moisture has been adequate or better disease can be found. Where spring wheat and winter wheat were planted into wheat stubble, Tan Spot can easily be found. In some cases the disease is severe and a fungicide application or including a fungicide with herbicide when the herbicide is applied would be appropriate. Some barley fields in Bowman and Stark Counties are exhibiting Spot Blotch and Net Blotch symptoms. In malt barley fields it is severe enough to consider applying a fungicide to control these diseases. Bacterial Blight on oat likely caused by Pseudononas can be found on the leaves giving a "burned" appearance to the field. If drying weather persists oat plants should recover.
Barley thrip were found in two Bowman County barley fields on Tuesday (June 18) by the Sheri Trumbull, IPM scout. Nine of the 50 stems that Sheri examined had barley thrip. Phil Glogoza earlier in this report discusses scouting and treatment thresholds for this pest.
Herbicide applications are proceeding with several days of low winds and ideal temperatures for application.
Canola that was seeded in mid-April is bolting and is beginning to flower. Large numbers of flea beetles have been found in some areas but in most cases the crop is far enough along to withstand the feeding pressure from this pest. Peas are progressing well. Both alfalfa and sweet clover are beginning to flower but flowering is less than one tenth bloom (1 stem flowering per ten stems). Some producers are beginning to cut alfalfa for hay.
Herbage production is short, even in areas where adequate moisture has fallen. Growers need to consider growing and harvesting annual forages to make up for the loss of production in pastures. Next week an article on why this shortfall has occurred and how producers can adjust stocking rates to minimize the effect on low herbage production in these pastures will be published in the ND Crop and Pest Report.
Area Extension Specialist/Cropping Systems
Dickinson Research Extension Center
During June 12 to 18, area rainfall ranged from 0.6 inches at McLeod and McHenry to 0.04 inches at Jamestown as recorded at NDAWN sites. Estimated daily crop water use on June 18 in south-central ND: corn (May 15 emergence) = 0.13-0.16 inches; wheat (May 15 emergence) = 0.19-0.23 inches; soybean (May 29 emergence) = 0.08-0.10 inches; and sunflower (June 5 emergence) = 0.09-0.11 inches. Additional rainfall is needed throughout the region, especially in counties south of I94.
Some sunflower and annual forages are still being planted. Crop conditions vary, depending on amount of recently-received moisture. In southern counties, early-seeded small grain generally is short (< 12 inches in height) and is heading. Farmers are debating whether to add additional imputs (e.g. weed control) and in extreme cases, whether to harvest wheat and barley for grain. North of Highway 200, crop conditions generally are good. Pasture and hayland conditions continue to be disappointing, especially in southern counties. Hay harvest has begun.
Herbicide application continues in late-seeded small grain, as well as in corn, flax and beans. Cutworms are reducing bean and sunflower stands in scattered fields. Sunflower growers should be monitoring for cutworm and sunflower beetle feeding. Tan spot is becoming common in wheat in areas that have received significant rain during the past couple of weeks. According to the NDSU small grain disease forecasting model, conditions favorable for tan spot infection were present 4 of 9 days during June 5-17 at Carrington. Disease forecasting models can be viewed at the following website:
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center