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Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Virginia Tech
Mr. Jack Speese (ESAREC Entomology Specialist) was hospitalized all week with pneumonia. We wish him the best. Get well soon, Jack!
Weather summary for week ending July 10, 2004 - Painter, VA
James T. Custis, Jr. (Farm Manager, ESAREC)
RAIN of 0.06" on 7/4, and 0.18" on 7/8. It is starting to get a little dry, but it is good potato digging weather. The reports I hear are still of more rain south of here and less rain to the north. Highs in the low to mid 80's early in the week and around 90 for the end of the week. Lows around 70 all week. We could use a little rain, but we also have a lot of potatoes still in the ground.
Blacklight and Pheromone Insect Traps
Tom Kuhar & Roberto Cordero (ESAREC)
Weekly catch:
Blacklight trap (BLT) in Painter, VA: 8 European corn borer, 9 beet armyworm, 9 corn earworm, 3 yellow striped armyworm, 8 true armyworm, 25green stink bugs, 67 brown stink bugs, 74 tobacco wireworm
No BLT data from Cheriton, VA this week.
Summary: Trap catch of most of the primary moth pests dropped this week. The major corn earworm (=bollworm) moth flight will probably start in a week or two. Stink bug (both green and brown) activity increased this week. Watch out for these insects in fruiting vegetables, soybeans, green beans, and cotton. Another flight of tobacco wireworm adults (click beetles) is occurring. These insects (along with flea beetles) should be sprayed in sweetpotatoes before they deposit eggs in the soil.
Cucurbit diseases
Christine Waldenmaier (ESAREC)
Downy mildew We have observed this disease on the Research Station this past week and it is occurring very early for our area. Downy mildew shows up as angular yellow lesions on the tops of the leaves. When the leaf is turned over, the lesion looks gray or tan and may have a gray mold fruiting. Once observed, fungicide control methods for this disease include alternating Cabrio, Pristine or Tanos every 14 days with Bravo, mefenoxam combinations or Acrobat plus Bravo or Mancozeb.
It is very important to realize that this disease can be hard to control during the weather conditions we are having right now. Be sure to apply fungicides such as Bravo or mancozeb preventatively and once observed to switch to the fungicides more effective on downy mildew.
Melon Diseases - Melcast
Kiptopeake area - Melcast for Alternaria, Gummy Stem Blight and Anthracnose has accumulated 19 EFI values for watermelon and 2 EFI for cantaloupe in the past two weeks. Under these conditions, fungicide sprays for these diseases can be stretched to a 14-day schedule.
Painter area - We have accumulated 50 EFI for watermelon over the past two weeks and 12 EFI for cantaloupe. Melcast would be calling for a spray in watermelons in this area if a field had not been sprayed since June 28th. Cantaloupes would be sprayed on a 14-day schedule.
Insect activity in cucurbit crops
Tom Kuhar (ESAREC)
Cucumber beetles: A swarm of striped cucumber beetles (5-10 beetles per young plant) were found on our fall cucumbers this week. The beetles can quickly defoliate plants and transmit bacterial wilt. Although most of the pyrethroid products will provide adequate control, we sprayed the aforementioned infestation with 3 oz/Acre of Actara (tiamethoxam), which is much less toxic to bee pollinators. We got excellent control of beetles.
Squash bugs are busy depositing their bronze egg clusters on pumpkins (especially no-till), squash and cucumbers. Plants should be sprayed if greater than 1 egg mass is found/plant. Insecticide sprays should target the small whitish to greenish gray nymphs on the undersides of leaves.
Melon aphids: After a week or so of not checking our no-till pumpkins at the ESAREC, melon aphids quickly have covered the undersides of leaves (and are way over economic threshold). An insecticide is recommended if more than 20% of leaves have live aphids.
Spider mite control in soybeans
Joanne Whalen (Delaware IPM Specialist)
Spider mite populations started to explode at the end of last week, so watch fields carefully for mites. We continue to see an increase in fields with visible spider mite damage, especially drought stressed fields. It will be important to scout the entire field before deciding if an edge treatment is enough. Early treatment is needed to achieve control once significant yellowing occurs it will be extremely difficult to achieve control and multiple treatments will be needed. A treatment is recommended if you find 20-30 mites per leaflet or 10% of plants with 1/3 or more leaf area damaged. At this point, the only materials available for mite control in soybeans are dimethoate and Lorsban. If dimethoate is used, the addition of a penetrating surfactant like LI-700 or Penetrator plus,or a material like Helenas Hyperactive should be used to improve control, especially in drought stressed fields. Multiple applications may be needed 5-7 days apart. At this point, dimethoate has been providing about 80% control. However, in fields that had mites present in the cotyledon, some are on their third application in Maryland. Remember, Lorsban only provides contact control, so multiple applications are needed 5-7 days apart. The addition of a crop oil has also improved control with Lorsban when applied by air.
Please keep us posted on how well dimethoate and Lorsban are performing.
Complete control may/will not be achieved with one application if populations have exploded or established at treatment time. There is no product out there that we have tested that can do it at this time using economic, labeled rates. Some have longer residual, but if you wait until high numbers are present and numerous eggs are present, you may still need multiple applications even with the newer products. If populations are declining, you may get away with one application, but that is all dependent on weather conditions. In many cases we may be limited to one application with these newer products if we can even get a soybean label (for resistance management and residue issues, so it is critical to scout and treat in a timely manner.
Mites on tomatoes
Tom Kuhar (ESAREC)
I'm hearing reports of spider mite and russet mite infestations on tomatoes in Virginia. Hot, dry weather will only exacerbate the problem. The russet mite is very tiny (often not seen with the naked eye), but will cause bronzing of leaves and stems and leaf dropping. Some effective miticides in recent trials on tomatoes include: Agri-Mek, Danitol, and Acramite.
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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