2011 CORN EARWORM SURVEY Chesapeake Office Agriculture Department 310 Shea Drive Chesapeake, Virginia 23322-5571 757/382-6348 FAX 757/382-6665 watsonl@vt.edu CHESAPEAKE FARMLINE August 2, 2011 The corn earworm (CEW) survey has been completed for eastern Virginia counties. The survey in Chesapeake revealed CEW in (29.2%) of ears sampled, and (20%) in Virginia Beach. That compares with 47.6% in southeast Virginia, making our survey somewhat lower than counties west of here. Last year CEW survey in Chesapeake was 56.4% and 57.2% in Virginia Beach. Over 30 years of data shows there is nearly a 1:1 relationship between CEW infestation in corn and the amount of soybean acreage that gets treated for this pest. This might point to lower pressure this year than 2010, but a lot can be influenced by rainfall and soybean canopy. A less than prolific canopy in many fields may promote egg laying by moths in coming weeks. The soybeans at greatest risk to earworm infestation are those: in drought stressed areas flowering or setting pods that have open canopies (late plantings/double cropped or poor stands) that have already been sprayed with a pyrethroid insecticide which eliminates beneficials For comparison statewide, 33% of corn was infested this year compared with 40% of corn in 2010. Last year was an intense CEW season followed by soybean looper infestation very late in the season. Last week, numbers of CEW moths caught in my blacklight trap started to rise, indicating a migration from corn to soybeans has begun. Moths are likely laying eggs in soybeans now so start to look for CEWs this week. Use CEW thresholds in chart on page 6 for determining when to spray. Count worms that are 3/8 of an inch or more in length. This allows for most egg laying and hatching to occur before treatment and reduces chances of needing subsequent sprays. Use soybean defoliation thresholds on page 6 for other insect pests. STINKBUGS We sometimes see problems with stinkbugs in soybeans before the CEW spray season begins. Stinkbugs usually fly in from woods and are found more commonly at edges of fields. If soybeans are setting pods, consider spraying with a pyrethroid if you find 2.4 stinkbugs in 7 to 21 rows or 3.6 stinkbugs in above 26 rows. You can consider spraying only field edges if that is the only area above threshold. Also be on the lookout for brown stinkbugs. See chart on page 6.
OTHER SOYBEAN PESTS TO SCOUT FOR BEAN LEAF BEETLE Foliage Feeder and Pod Scaring - These beetles can be either green, yellow, tan, or red with a dark triangular shaped marking behind the head. They chew on edges of soybean leaves causing a ragged appearance. We spray based upon percent defoliation. Later in the season, as pods become full and numbers of bean leaf beetles build upon second generation, they may scar pods, especially in fields that have not had a CEW spray. Fields receiving a CEW spray will knock back bean leaf beetles to numbers that generally do little pod scaring. We know it takes a lot of bean leaf beetles (no thresholds developed yet) and they do not scar pods till later in the season. When you are scouting for CEW later in the season, do not forget to take into account defoliation or observed scaring of pods. Refer to page 4-62 of the PMG for insecticides. See chart on page 6 GRASSHOPPER Foliage Feeder Grasshoppers can cause damage along hedgerows and areas where they may have moved into a field. They are foliage feeders. If you see a problem, you may only need to treat along the field border. In a field with heavy foliage loss, use the same thresholds as for bean leaf beetles and other defoliators. Refer to page 4-70 of the PMG for insecticides. See other defoliators in chart on page 6. SPIDER MITES Foliage Pest - Two-spotted spider mites can become a troubling pest, usually in drought stressed soybeans. You will usually find spider mites along field edges where grass has been mowed. They will move into field and cause yellow stripping of leaves with brown speckling. You will need a hand lens to see them. Spray if you see 50% or more plants with spider mites. Sometimes a spot treatment is all that is needed along a field border. Lorsban 4E at 0.5-1.0 pt/acre or Dimethoate 4EC at 1.0 pt/acre is recommended. See chart on page 6. GREEN CLOVERWORM Foliage Feeder Green Clover-worm is the most common worm we see when scouting soybeans. They rarely require a treatment as they generally do not defoliate enough to harm soybeans. They often are confused with the Soybean Looper because of their green color and the way they move in a looping style. Green cloverworm wiggle vigorously when disturbed. See chart on page 6. CORN Bt TRAIT TABLE:by Chris Difonzo-MSU & Eileen Cullen-University of Wisconsin The table on page 5 lists commercial insecticide trademarks, multiple transgenic traits they contain, and the insects they control. This table can help farmers understand what pests are controlled by different stacked traits. The refuge requirements are based on the midwest. Consult the refuge requirements on page 4-36 in the PMG for Virginia. KEY Insects Herbicide Traits BCW black cutworm ECB European corn borer GT glyphosate tolerant CEW corn earworm FAW fall armyworm LL Liberty Link/glufosinate CRW corn rootworm SB stalk borer RR2 Roundup Ready/glyphosate WCB western bean cutworm
2011 VIRGINIA WHEAT CHALLENGE STATEWIDE WINNERS Place Grower Farm County Yield bu/ac Variety 1st Frank Hula Riverside Farm Charles City 129.5 Shirley 2nd John P. Shepherd Tri-County Grain Nottoway 120.9 USG 3555 3rd Bill Nelson Colonial Acres Henrico 120.3 Roane 4th Craig Brann Brann Farms Richmond 118.0 Shirley
CORN EARWORM ECONOMIC THRESHOLD CALCULATOR Go to this web site to better estimate your threshold based on costs of application and price of soybeans: http://www.ipm.vt.edu/cew/ Example: Soybeans planted in 21-inch rows, booked at $13.00/bu. costing $10.00/acre to spray has a threshold of 1.47 worms. Those same 21-inch row soybeans sold at 10.00/bu. costing same amount has a threshold of 1.91 worms. VIRGINIA DARE SWCD COST-SHARE SIGN-UP Farmers are reminded the deadline to sign up for state cost-share practices ends August 19. For information, call Roy Flanagan at the SWCD office in at 385-8607. Some of the most popular practices are: Annual Cover Crop; Harvestable Cover Crop; Continuous No-Till; Nutrient Management Plans; Sidedress of Nitrogen on Corn; Split Nitrogen on Wheat; Conversion of Cropland to Pastureland; Water Control Structures; Integrated Pest management. If you are a person with a disability and require any auxiliary aids, services or other accommodations for any Chesapeake Extension event, please discuss your accommodation needs with the Extension staff at (757) 382-6348 at least one week prior to the event. The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by Cooperative Extension is implied. If you need additional information, please give us a call. Sincerely, 1. Only count worms 3/8 inch long or longer. 2. Based on a 15-sweep sample Sampling tool Row Width Rows Sampled Threshold 7 5 2.5 Sweep Net 2 21 2 3.1 14 3 2.4 36 1 3.1 SOYBEAN DEFOLIATION PEST THRESHOLDS # per 15 sweeps row-spacing 7 21 Above 21 Other comments Stinkbugs 2.4 3.6 Little damage after beans are fully formed. Bean leaf beetles Spider mite Based on defoliation or evidence of pod scaring Damage occurring and live mites present 20% defoliation pre-bloom 10% defoliation pod-fill 15% defoliation fully developed seeds Live mites on 50% of leaves and 50% leaves showing white spotting or premature leaf drop. Other 20% defoliation pre-bloom defoliators 1 10% defoliation pod-fill 15% defoliation fully developed seeds 1 Other defoliators include any combination of green cloverworm, bean leaf beetle, blister beetle, Japanese bettle, soybean looper, yellowstriped armyworm, grasshoppers, or fall armyworm. M. Watson Lawrence, Jr. Extension Agent, Agriculture