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Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Virginia Tech
Weather summary for weeks ending July 2, 2004 - Painter, VA
James T. Custis, Jr. (Farm Manager, ESAREC)
WET!!!! RAIN of 0.74" on 6/26, 0.66" on 6/28 and 0.90" on 6/30. This has stopped our field work at times. We had to modify our field day plans due to the rains. The reports I hear are of more rain south of here and less rain to the north. Highs in the upper 70's to low 80's and lows in the low to mid 60's. We have had a little more rain than we need but we don't want it to stop as it starts to get hot again.
Blacklight and Pheromone Insect Traps
Jack Speese & Tom Kuhar (ESAREC)
Weekly catch:
Blacklight trap (BLT) in Painter, VA: 20 European corn borer, 28 beet armyworm, 28 corn earworm, 9 yellow striped armyworm, 6 green stink bugs, 35 brown stink bugs, 6 tobacco wireworm
BLT in Cheriton, VA: 26 ECB moths, 40 beet armyworm, 60 corn earworm, 2 yellow-striped armyworm moths, 0 stink bugs
Summary: We are still seeing a moderate 2nd generation ECB flight now on the Eastern Shore. Also, corn earworm, yellow striped armyworm and beet armyworm moths are active. These insects will be laying their eggs on a broad range of host crops. Pigweed is one of the most attractive host plants for beet armyworm, so check that weed for larvae. Beet armyworm will quickly strip pigweed of all of its leaves if you have a moderate density of the pest around in your fields. As mentioned last week, the infestation levels of beet armyworm and corn earworm this summer primarily will be determined by the weather over the next couple of months. Hot and dry will likely lead to problems, whereas, wet weather will often result in disease epizootics that will knock the pest population down - as occurred last year in much of the Eastern U.S. We'll keep you posted.
Cotton Insect Pest Update
Ames Herbert
Plant bug/stinkbug: We are doing weekly plant bug/stinkbug surveys of 23 cotton fields throughout the cotton counties (Suffolk - 8 fields; Southampton 9 fields; Isle of Wight 5 fields; Dinwiddie 1 field). As of this week, only 4 have dropped below the 80% square retention rate (and one of those was just below at 79%). Overall, most fields are in the 90% + range, which indicates a strong cotton crop going into flowering. Much of our cotton is beginning to bloom so we will begin transitoning from square retention counts to looking for dirty blooms (see below).
We are concerned about what may be a continuing problem with plant bug. A lot of adults are still developing in weeds like daisy fleabane that border fields and roadsides, and these adults will continue moving into cotton fields.
We are seeing some brown stink bugs in some fields. The population was extremely large in small grain and adults may continue to infest cotton. Research at Louisiana State University showed that stinkbugs, in general, do not damage squares but focus on bolls as they probe to feed on developing seed. Therefore, treatments in pre-bloom or blooming cotton for stink bug may be misdirected. If brown stinkbugs occur during boll formation, they will represent a threat and need to be controlled.
Dirty blooms: It is now time to shift to inspecting blooms and new bolls for damage from bugs. Blooms that show brown streaks, specks or are deformed are referred to as dirty bloomsand were most likely fed upon by plant bugs while in the square stage. Dirty blooms are an indication that plant bugs are in the field. The number or percentage of dirty blooms may be a relative indicator of how large the plant bug infestation is, but it is difficult to base a spray decision on that percentage. 15% dirty blooms is considered a threshold, but only if the presence of plant bugs is confirmed with sweep net sampling. I suggest that presence of dirty blooms just be an indicator that a more intensive inspection of young bolls is needed.
Bollworm flight: We are definitely seeing evidence of the first small corn earworm flight. We have trapped over 500 moths in our pheromone trap system over the eastern side of the state, just since mid June. The blacklight catch is still very low, less than 2 per night, but that is typical as pheromone traps usually do a better job of catching moths early in the season. We will begin spot checking cotton fields next week for eggs.
Aphids: We are hearing of aphids in some fields. Aphids are being reported from Alabama to Virginia. A few growers in North Carolina have had to treat. The fungus that attacks aphids has been reported in Georgia. In Virginia, most the infestations are spotty with scattered plants infested. Lady beetles and parasitic wasps are active and eliminating some of these problems. If soils stay moist and conditions continue to favor the development of the aphid fungus (good rains and humidity), we may escape the need for sprays.
Peanut Insect Pest Update
Ames Herbert (Tidewater AREC)
Peanuts are growing well and the unusually warm temperatures during May and June have resulted in 200+ heat units over what we had at this time last season.
Potato leafhopper: Leafhoppers are beginning to show up in a lot of fields. If you plan to apply Lorsban 15G or any chlorpyrifos insecticide for rootworm, this application will control leafhoppers for several weeks. Fields where rootworm insecticides are not being applied need to be scouted for active hopper populations and level of leaf damage. Our thresholds state that a treatment is justified if 25% of the leaves show hopper burn and they are still active. The best time to scout is just prior to a leafspot or other fungicide application. Leafhopper insecticides (consult your VA Peanut Production Guide for a list of options) can be tank mixed to reduce application costs.
Thrips and tomato spotted wilt virus: The symptoms of tomato spotted wilt virus are now starting to show up in a lot of fields. As the weather becomes hot, the plants will be stressed and many more plants with symptoms will begin to appear. This does not mean that the virus is being spread by thrips, but rather it was infected early and the signs are just starting to show. DO NOT apply additional insecticide for thrips control if you start to see a lot of virus. You will be wasting money.
Southern corn rootworm: We always recommend using the revised Peanut Southern Corn Rootworm Advisory (http://www.ext.vt.edu/pubs/entomology/444-351/444-351.html) to determine if fields need to be treated. If you plan to treat for rootworms but have not, now is the time to get that treatment on the field.
Snap bean insect control
Tom Kuhar (ESAREC) and Joanne Whalen (U. Delaware)
All seedling stage beans should be scouted for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet, and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3. Dimethoate, Lannate, Asana, Capture, Mustang Max or Warrior will provide control of both insect pests.
Once beans reach the bud to pin stage, on fresh market snap beans a spray program is recommended to control European corn borer, thrips and/or bean leaf beetle, which can damage pods. We are in the middle of a peak 2nd generation ECB flight right now in Eastern VA. A 7-10 day schedule should be maintained for corn borer control. Products such as Acephate (Orthene), Lannate, Asana, Capture, Warrior or Mustang Max are labeled. Acephate has a 14-day wait until harvest.
Sweet corn insect management
Tom Kuhar (ESAREC)
In eastern Virginia, for effective protection of ears, it is recommended that all sweet corn that has reached the fresh silk stage should be sprayed with an insecticide (usually a pyrethroid) at least every 5 days until harvest. We are picking up corn earworm moths already, and European corn borers are in 2nd generation flight. Our research has shown that Bt sweet corn varieties have worked great and for early-plantings, at least, Bt varieties should not need an insecticide spray. Later plantings of Bt sweet corn may benefit from 1 or 2 well-timed sprays to get maximum protection.
Yellowing Soybeans Can Be Symptoms of Several Different Problems
(Copied from the Delaware Weekly Crop Update, Volume 12, Issue 14 June 25, 2004)
Derby Walker (Delaware Sussex County Extension Ag Agent)
Yellow soybeans can be a symptom of several different problems including pH, insect, diseases, nutrient deficiencies or nematodes. This week, I have found spider mites and thrips in one field. Leafhoppers are another insect that can cause soybeans to yellow. One field had several spots showing manganese deficiency, most likely caused by high ph. The beans were blooming and needed to be sprayed with a foliar manganese product to correct the problem. A couple of fields were dropping their older leaves because of a minor leaf spotting disease. It looks like Septoria Brown Spot.
Three fields appeared to be nitrogen deficient. They were nitrogen deficient, but the problem was soybean cyst nematodes that prevent nitrogen fixing nodules from developing. They were soybean cyst resistant but they were not resistant to the Race in these fields. Planting same race resistant beans year after year will shift the race of cysts to another race most likely to Race 1 or Race 5. How can you tell which it shifted to? Hoe out a section of beans where there is cyst problem and plant varieties that have different Race resistances (non-resistant, Race 3, Race 1, and any other race you can find). Then 30 to 35 days later dig up of plants and count the number of cyst on each variety. The one with fewest is type of resistant beans you need. The odds are good that Race 3 shifted to Race 1. We do have some Race 1 resistant varieties, however most are very late group 4 or group 5 beans. Also you will probably have to return to standard soybean varieties and herbicide programs instead of Roundup Soybeans.
Even combining glyphosate with certain herbicides and other products can give you a temporary yellowing and sometimes a stunting.
Thomas P. Kuhar
Assistant Professor
Department of Entomology
Eastern Shore Agricultural Research & Extension Center
Virginia Polytechnic Institute & State University
33446 Research Drive
Painter, VA 23420
E-mail: tkuhar@vt.edu
Tel: 757-414-0724
FAX: 757-414-0730
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