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Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Virginia Tech
Greetings crop producers, researchers, extension personnel, and crop consultants,
Weather summary for week ending June 4, 2004; Painter, VA
James T. Custis (Farm Manager, ESAREC)
TIMELY RAIN last week and 0.74" from Sunday pm to Monday, which slowed field work the first half of this week. The rest of the week had great field working conditions, good soil moisture, cooler temperatures and light winds. Not all areas on the Shore have had things this good!
Highs from the low 70's to mid 80's and lows from the mid 50's to low 70's.
Blacklight and Pheromone Insect Traps
Jack Speese & Tom Kuhar (ESAREC)
Weekly catch:
Blacklight trap (BLT) in Painter, VA: 0 European corn borer moths, 2 cutworm spp., 2 true armyworm, 1 yellow-striped armyworm, 0 corn earworm, 5 green stink bugs, 0 brown stink bug
BLT in Cheriton, VA: 13 ECB moths, 2 cutworm spp. (mostly black cutworm), 6 corn earworm, 1 true armyworm, 2, yellow-striped armyworm, 4 green stink bug
In summary, the first generation European corn borer moth flight has dropped off on the Eastern Shore of VA. Stinkbug activity has also dropped off.
Potato Disease Control
Christine Waldenmaier (ESAREC)
Early blight - Conditions for early blight infection have become more favorable. Early blight causes a spotting of the leaves and will only effect yield if it occurs early in the season and with enough severity to impact filling of the tubers. Many seasons early blight doesnt build up until mid-June, late enough that yields of early planted potatoes will not be affected. For potatoes that are not bulking yet, chlorothalonil or mancozeb will control low levels of infection. If you can see a lot of necrotic spotting on the leaves already, and the return on the investment justifies a spray, Quadris or Headline would be the products of choice.
Black leg - This disease is caused by a bacterial infection of the seedpiece which moves up the stem causing a black decay extending up the stem from the soil surface. Blackleg is favored by cool and wet soils at planting followed by high temperatures after plant emergence. Fields with a lot of blackleg need to be harvested with more care to minimize secondary spread of the bacteria to healthy tubers. Harvest tubers that have the skins set, prevent bruising when harvesting, and prevent heat build up by harvesting in as cool a temperature as possible and by covering transport trucks. There is no chemical control specific for this disease, however by planting well-healed seed and by the applying seedpiece treatments bacterial rot can be minimized.
Potato insect pest update
Tom Kuhar (ESAREC)
We are seeing heavy potato leafhopper numbers and hopperburn on our untreated potato plots in Painter. This insect can severely impact yield if not controlled. Most growers used Admire, Platinum, or Gaucho at planting, and these materials should provide effective control of PLH. If a rescue foliar spray is needed, then a low rate of dimethoate or a pyrethroid should do the trick for an affordable price. PLH are not hard to kill. There are also a lot of European corn borer tunnel holes in the plants of unsprayed plots. It is probably past the time to spray a foliar for European corn borer. Once theyre in the plant it is too late. Were not seeing anymore ECB egg masses deposited on leaves.
In addition, new F1 generation Colorado potato beetle adults are swarming on untreated potatoes as well. The Admire, Platinum, Gaucho, and Cruiser plots treated at-planting are still holding up with enough insecticide still in the plants to control these adults.
Cucumber beetle management
Tom Kuhar (ESAREC)
Cucumber beetles (striped and spotted) infest cucurbit crops (melons, cucumbers, pumpkins, and squash) every year in Virginia, and typically become active in late May. Beetles can aggregate in a field quickly, so crops should be inspected daily, particularly when plants are young. We have seen a few beetles at the station already aggregating on our cucumber plots. If beetles are not controlled, economic losses to crops may result from beetles defoliating and killing seedlings or transmitting bacterial wilt, particularly to cucumbers and muskmelons.
Losses from bacterial wilt vary greatly among varieties and from field to field. Because of their small size and leaf area, cucurbit seedlings and transplants are very difficult to spray efficiently with conventional equipment. At-planting systemic treatments are recommended for cucurbit crops that are susceptible to bacterial wilt. Systemic insecticides that have provided effective control of beetles and bacterial wilt in past trials include: Furadan 4F at 3.8 fl oz/1,000 ft of row (Special Local Needs 24c Label for Virginia), and Admire 2F (16 fl oz/A) or Platinum 2SG (8 fl oz/A) as a drip irrigation injection or transplant drench treatment. Although these treatments are effective, they are somewhat expensive. Several labeled pyrethroid compounds (Asana XL, Capture, Ambush, and Pounce), also provide effective beetle control as foliar sprays and are usually less expensive than the aforementioned at-planting treatments. If pyrethroids are used, fields should be monitored weekly for re-colonization by beetles. A grower should consider the following when deciding on a management strategy: 1) bacterial wilt susceptibility of the cucurbit variety; 2) history of beetle pressure on the farm; and 3) time and resources available to monitor fields and apply a rescue foliar spray if needed.
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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