FROM AROUND THE STATE
ISSUE 6 June 7, 2001
INSECT AND DISEASE PEST UPDATE
More Cutworms and Wireworm Reports!
Numerous fields damaged by cutworm and wireworms are being reported on several crops -- corn, sunflower, canola, chickpea, to name a few. The early season cutworms, like Dingy cutworm, are mature and a large 1.5 inches larvae (worm). These cutworms will pupate in the soil soon and no longer be feeding. However, the late season cutworms, like the Red-backed cutworm, are also being found and in the early instars larvae, <1 inch long. These cutworms will continue to feed until late June depending on temperature. The economic threshold is a 25% stand loss. Wireworms have also caused significant damage to crops, for example, a 500 acres sunflower field was destroyed in Parshall, Mountrail County. Wireworms are active until the soil temperatures warm up to 80oF. Most soil temperatures are barely near 60oF in the north central region! So, wireworm will continue to be active especially with adequate soil moisture. If you replanted into wireworm infested soil, please use a seed treatment with an insecticide (Lindane) to protect your crop!
Crucifer Flea Beetle: For the north central region, flea beetle activity continued into this week with trap catches slightly decreasing from last week. Some later planted canola fields are being treated with Capture (FMC). Early planted fields should be getting pass the 6-leaf stage and will hopefully outgrow future flea beetle attack.
Diamondback moths (DBM) larvae were observed feeding on canola in the 2 leaf stage near Velva and Sawyer in McHenry County and near Glenburn in Renville County. Some plants had as many as 6 larvae per plant and caused over 50% defoliation. Pheromone traps set out in early May have captured DBMs earlier and in higher numbers than last year. There is no economic threshold for DMB larvae in young canola plants, but 25% defoliation in canola less than 4 leaf stage can impact yield. For field identification, the larvae are lime green in color with a forked posterior end, and about a ½ inch when mature. When disturbed, the larvae also have the peculiar habit of dropping down from a plant on a silken thread. Check fields for DBM larvae! Capture 2EC Insecticide is registered for control of DBM at the 2.1-2.6 fl oz rate per A. DBM infestations are spotty. One field can be infested and the field across the road will be untouch! With the recent scattered thunderstorms, some DBM larvae may have been washed off the canola leaves and drowned!
Sunflower beetles are now feeding on sunflowers in the seedling to 2-leaf stage. Check fields for 1-2 adults per seedling as a guide to determine whether or not a field needs to be treated.
Tree & Shrubs
Prairie tent caterpillars have been observed feeding on hardwood trees especially chokecherries in the Minot area. Look for the unsightly web nests in the forks of trees. Larvae are 1 inch long, and pale blue with an interrupted white stripe bordered by two reddish-orange stripes down the center of the back. Larvae feed on leaves for 5-6 weeks outside the nest. In low levels of infestation, nests can be physically removed from the trees and destroyed. Cyfluthrin, Acephate, Diazinon, permethrin, Sevin and pyrethrins are a few of the insecticides labeled for use against tent caterpillars in ND.
Tan spot can be readily observed on small grain fields. The incidence and severity are higher on wheat on wheat fields compared to wheat on alternative crops like pea, canola, for example.
Bacterial blight, yellowing-browning of the leaf tip, is also common from the severe winds this spring.
Janet J. Knodel
Area Extension Specialist Crop Protection
North Central Research and Extension Center
During the past week (May 30 to June 5), rainfall recorded at NDAWN sites in south-central North Dakota ranged from 0.35 inches (Carrington, Jamestown, Streeter, and Edgeley) to 0.78 inches (Linton).
Across the region, cool-season crop seeding is essentially complete. Sunflower and annual forage crops are being planted throughout the area. Soybean and dry bean planting is nearly complete south of I-94, but continues in the northern counties. Crop stands generally are adequate. Based on growing degree day units, spring wheat emerged on May 1 was in the jointing stage and wheat emerged on May 15 was in the 4- to 5-leaf stage as of June 5. Higher air temperatures are desirable to promote growth of warm-season crops. Alfalfa harvest has begun in southern counties and will be a general activity when ‘haying weather’ is present.
Reports of crop insect and disease problems are low. Scattered canola fields have been treated for flea beetle. Weekly counts of flea beetle in sticky traps at the Carrington Research Extension Center have recently increased but are still low. Diamondback moths have been detected in pheromone traps in low numbers since mid-May. Evidence of weevil feeding in alfalfa and sweetclover was found in McIntosh County. Young grasshoppers are being detected in field margins. Tan spot can be more easily found in wheat fields but the disease generally is at low levels. During the past week, it has been very difficult to apply POST herbicides in small grain, canola, and corn due to windy and wet weather conditions.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center