|
|
|
Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Virginia Tech
Weather summary for week ending July 16, 2004 - Painter, VA
James T. Custis, Jr. (Farm Manager, ESAREC)
RAIN of 0.42" on 7/12, 0.02" on 7/14 and 1.05" on 7/14. It is a little wet here now but we have had good potato digging weather this week until the rain Wednesday night. High temperatures in the mid to upper 80's this week and lows in the low to mid 70's until Thursday, then lows in the mid 60's.
Blacklight and Pheromone Insect Traps
Tom Kuhar & Roberto Cordero (ESAREC)
Weekly catch:
Blacklight trap (BLT) in Painter, VA: 6 European corn borer, 5 beet armyworm, 3 corn earworm, 6 true armyworm, 42 green stink bugs, 52 brown stink bugs, 20 tobacco wireworm
BLT data from Cheriton, VA: 3 European corn borer, 3 beet armyworm, 1 corn earworm, 36 true armyworm, 6 green stink bugs, 9 brown stink bugs, 7 tobacco wireworm.
Summary: We are still pretty much in a lull as far as pest moth activity - very few corn earworms, corn borers, or armyworm species were caught this week. The major corn earworm (=bollworm) moth flight will probably start in a week or two. Stink bug (both green and brown) activity is still high. These insects can cause serious damage in cotton and fruiting veg
Soybean aphid Alert!
Ames Herbert (Tidewater AREC)
As part of our statewide soybean rust survey, we are also surveying for soybean aphid. As of this week, we have confirmed the occurrence of soybean aphid in 19 counties (Accomack, Northampton, Lancaster, Northumberland, King William, King & Queen, Mathews, New Kent, Charles City, Henrico, VA Beach, Chesapeake, Suffolk, Southampton, Greensville, Goochland, Amelia, Nottoway and Powhatan).
These are not large infestations, just a few aphids on a few leaves, but it is important to take note of this as populations could increase. As a follow up note later this week, we will send out a list of the actual fields where aphids have been found so the respective agent for that county and the grower can be alerted. Our survey is structured so each field is visited every other week. This may not be adequate for monitoring these aphid populations but it is the best we can manage given the statewide scope of our survey and the number of fields involved. We strongly encourage agents and growers with fields known to have aphids to take a role in inspecting their own fields.
What to look for and what to do? We have provided a lot of information on soybean aphid at past meetings and on the web (www.ext.vt.edu/pubs/entomology/444-202/444-202.html), and the University of Minnesota has a good soybean aphid website at www.soybeans.umn.edu/crop/insects/aphid/aphid.htm. Basically, if you find wingless aphids on soybean leaves or stems, light to dark yellowish in color, especially if in colonies of 2 or 3 or more, you have soybean aphid. This is the only known aphid species that develops on soybean. Under the right conditions, they can reproduce very rapidly going from 10 to 1000 per plant in less than 2 weeks. They prefer somewhat cooler temperatures, 68-77 °F, so may not build up rapidly given our rather hotter summertime temperatures. They are also subject to predation by several insects like lady beetles, lace wings and others. Hopefully, the combination of hot weather and action by these natural enemies will prevent economic aphid levels, but we wont know unless fields are monitored.
However, this early occurrence of aphids does present a potential threat. Last year when they invaded Delaware in July, by early August they had developed into very large populations to require some insecticide treatments by growers.
What are the threshold and how to scout? Current thresholds developed in western states where soybean aphid has been a constant pest state that treatment is needed if numbers exceed 250 per plant up through R4 (full pod) soybean growth stage AND the population is increasing, natural enemy populations are low, cooler temperatures (75-89 °F) are common, and plants are under drought stress. After R4, threshold increase to 1000-1500 aphids per plant. It takes some effort to scout aphids. Cover a field inspecting 20-30 plants. Make whole plant counts, but pay special attention to the terminal (top) growth as aphids prefer this area of the plant. Check stems, petioles and undersides of leaves. Late planted, double crop fields are at the greatest risk to infestations so, scout those fields first.
What to treat with? If an economic threshold is met, several insecticides have proven effective in controlling soybean aphid. All of the pyrethroids labeled for soybean do a good job. Two non-pyrethroids, Lorsban 4E and Penncap M, are also labeled and do a good job.
Stay tuned. We will be forwarding updates on soybean aphid as we continue monitoring fields.
Insect activity in cucurbit crops
Tom Kuhar (ESAREC)
Cucumber beetles: Striped cucumber beetles are still re-colonizing our melon crop (even after foliar insecticide applications.
Squash bugs are busy depositing egg clusters on cucurbit crops (especially pumpkin and squash). Some eggs have begun hatching and it is now optimal time to target a control spray. Plants should be sprayed if greater than 1 egg mass is found/plant.
After applying pyrethroids to pumpkins, we had flairs of melon aphids (several hundred per leaf) - aphid densities were two to three times higher than on untreated plants. Some effective melon aphid control products include: Fulfill (Homopteran feeding inhibitor), the neonicotinoids - Admire, Platinum, and Actara, as well as Lannate and Thionex. The latter two will have a harder impact non-target organisms such as pollinators and natural enemies. An insecticide is recommended if more than 20% of leaves have live aphids.
Beet armyworm alert
Tom Kuhar
As the moth catch from a few weeks ago predicted, we are seeing a few outbreaks of beet armyworm on the Eastern Shore. Crops that have been attacked include: peppers, cotton, cucurbits, soybeans, and tomatoes. Fall potatoes, spinach, and cole crops are also host plants for beet armyworm. The most attractive host plant for beet armyworm is pigweed. Infestations often will start on these weeds and then larvae will crawl to other plants. Color patterns of the larvae can be quite variable for this pest. Young larvae are pale green or yellow, but acquire pale, then dark stripes as they get older and larger. Large larvae tend to be darker - green dorsally and possess a lateral dark stripe the length of their body. In 2002, beet armyworm populations were moderately resistant to pyrethroid insecticides. The pest was adequately controlled with Bt products -(especially if smaller larvae were sprayed), as well as indoxacarb (Avaunt, Steward), spinosad (SpinTor, Tracer), Intrepid, and Proclaim. Lannate and Larvin provided moderate control. Some of the aforementioned chemicals are not labeled on certain crops. As always, read the label before applying any pesticides.
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
Return to Crop Pest Advisory