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Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Eastern Shore AREC, Virginia Tech
Greetings crop producers, researchers, extension personnel, and crop consultants,
Welcome to new subscribers and contributors.
Blacklight and Pheromone Insect Traps on the Eastern Shore
Jack Speese & Tom Kuhar (ESAREC)
As we did in 2003, two insect blacklight traps will be monitored this year on the Eastern Shore of VA. Mr. Bill Shockley, agricultural extension agent in Northampton County, will monitor a trap near Cheriton,VA and we are monitoring one at the ESAREC. In addition, as the season progresses, we will monitor pheromone traps for stinkbugs, corn earworm and fall armyworm. Temperatures were a little cool in the evenings this week, and very little insect activity was recorded.
Potato weed management
Jason C. Sanders & Henry P. Wilson (ESAREC)
Dual plus Sencor is the standard preemergence (PRE) herbicide application for potatoes. However, emerged potatoes that receive a Dual plus Sencor application will likely show some visual injury. Do current weather patterns forecast a repeat of last year's difficulty in early-season herbicide applications in potatoes? It is difficult to say, but the forecast for next week indicates several days with rain. Due to wet field conditions, spring herbicide applications on potatoes may go out later than usual. If applications are delayed, potatoes will likely be emerging or about to emerge. There are still herbicide options for weed control, even with delayed applications on emerging potatoes. Three different options that can be used to minimize this potential injury include:
When faced with the decision of what to do, one should take into consideration the percent of potatoes emerged following the cultivation. A normal tank-mix combination of Dual plus Sencor can be considered when less than 15% of the potatoes have emerged, and rates could be slightly reduced for added crop safety. As the percentage of emerged potatoes increases, so does the potential for temporary injury. With an increase of emerging and exposed potatoes that are more susceptible to herbicide injury, the chances that a delay in maturity will be encountered becomes more possible. When catching up to spray later planted potatoes that are not emerged, the normal approach to dragging-off and then spraying PRE herbicide applications can be followed.
One very important thing to keep in mind about reducing PRE herbicide rates is the possibility of a reduction in weed control. If rates are reduced, weed control can decline as the season progresses. These later emerging weeds will probably not lower yields, but can interfere with harvesting and reduce potato quality. If PRE herbicide rates are reduced, there is the option of applying Matrix postemergence (POST) to control some broadleaf weeds and aid in the control of yellow nutsedge. Matrix applications should preferably be made before the weeds and potatoes get too large. Escaped grasses can be controlled with Poast or Select applied POST. If you are faced with controlling weeds with postemergence herbicides, do not forget to use the appropriate adjuvant in this application.
Northampton County news from our roving reporter in the field
(Bill Shockley (VCE, Northampton Co.)
Plantings of field corn, string beans, squash, tomatoes, peppers and sweet corn are progressing. Weather is drier and cooler than normal with nightly lows, in some instances, in the mid 40's. Small grain is progressing very well with a few signs of mildew and spindle streak occurring primarily in the variety Century II. The Northampton weekly meetings will begin on Wednesday April 14, at 6 AM in Capeville at the Cape Center and at Noon at Little Italy in Nassawadox. The Black Light Insect Monitoring program will begin next week as well as the Potato Late Blight Monitoring Program. Thanks to the support of the following organizations, we have purchased a new potato monitor to be located in lower Northampton County which will give us monitoring capabilities from Kiptopeake to New Church:
The Association of Potato and Vegetable Growers
The Virginia Irish Potato Board
The Northampton County Farm Bureau
UAP Northeast, Inc.
Shore Fertilizer Corp.
Royster-Clark, Inc.
Helena Chemical, Corp.
Many thanks to these folks for their support of agriculture on the Shore.
This year we will conducting several on farm tests in Northampton County to assist Virginia Tech research individuals. A few of these include the following:
Dr. Tom Kuhar, Insect Sampling and Insecticide Trials - Various Crops
Dr. Henry Wilson, Field Corn Texas Panicum control tests.
Dr, Steve Phillips, Variable Rate Crop Density Nitrogen Applications to field corn.
Dr, Mark Alley and Dr. Steve Phillips, Small Grain Miconutrient Fertilization tests
We are very fortunate to have this important research work being done in Northampton County.
Wheat disease update
Dr. Erik Stromberg (Plant Pathology, Virginia Tech) and Christine Waldenmaier (ESAREC)
Viruses -
Virus infected wheat leaves are usually paler in color than healthy leaves, with yellow streaks and/or spots and sometimes a reddish leaf margin or a purple leaf tip. (These symptoms can mimic Manganese deficiency if soils have been treated with sludge and the pH has gotten too high.) If the symptoms are due to virus, by the time they are observed, it is too late to do anything to control the disease. Viruses require another organism for disease transmission. Depending upon the virus, this organism may be an aphid, a mite or a fungus. Most of the time the infection that occurs in the autumn accounts for the symptoms seen this time of year. For this reason planting in late autumn reduces infection. Barley yellow dwarf, the most common virus, is transmitted by aphids, which can be partially controlled at planting with Gaucho seed treatments. Other viruses such as wheat spindle streak (see http://www.ppws.vt.edu/stromberg/smallgrain/biology/wsstreak.html) and soil borne mosaic virus are vectored by a soil fungus and infections occur during cool wet periods in the autumn. Symptoms of these viruses are seen in the Spring when temperatures are cool - like we've had recently. Once the temperature increases to above 60 F - symptoms disappear. The best way to control these viruses is to select resistant cultivars if available.
Powdery mildew -
Powdery mildew fungicide treatments shouldn't be applied until after first joint (GS-6).
Many of the newer varieties have adult-plant powdery mildew resistance and the mildew won't progress up the plant as it grows. Unless mildew is already very heavy on the lower leaves, it is better to wait until the flag leaf has emerged or later (GS 8-10.5) for better control of other diseases in addition to powdery mildew.
Corn insect pest management considerations
Rod Youngman (Dept. Entomology, Virginia Tech) & Tom Kuhar (ESAREC)
Many growers will be planting corn soon and are wondering whether or not an at-planting insecticide is needed. Soil insecticides, such as Lorsban, Counter, Force, Fortress, and Regent can protect the crop against several different pests, most importantly, corn rootworms, wireworms, annual white grubs, and seedcorn maggot. Corn rootworms can be a serious economic pest in continuous corn. However, because their eggs are laid predominately in cornfields and larvae can only survive on corn, crop rotation is an excellent control measure. So, corn planted after any other summer crop should not have problems with rootworms. If corn is following pastureland, sod, or a weedy fallow field, then wireworms in particular, as well as white grubs may likely be a concern. Also, about 15-20% of fields planted into corn after soybeans typically experience problems from white grubs. Seedcorn maggot is primarily a problem in fields with high organic matter (manure applied) and or during cool wet springs, when seed germination is delayed. However, the three aforementioned pests are unpredictable and may infest various fields for unexplained reasons.
Research conducted in the early 1990s and for the last two field seasons in Virginia has validated the effectiveness of pre-plant sampling with the baited wire trap (BWT) method to detect the presence of wireworms, white grubs and seedcorn maggot. The BWT method consists of placing 20 untreated corn seeds (pre-soaked in water for >12 hours to facilitate germination) spaced evenly along a 3-inch wide by 24-inch long strip of hardware cloth (1/4-inch mesh). The hardware cloth strip is bent lengthwise along a 90-degree angle to provide strength and to keep the seeds in place. The BWT (with seeds) should be placed in a furrow about 2-3 inches deep and then covered with enough soil to produce a slight mound. The soil over the trap should be lightly tamped down. Be sure to mark the location of each BWT with a flag. In addition, a black plastic cover (trash bag) should be placed over the BWT if installation is being done during extended periods of cool conditions (i.e., when maximum daily air temperatures are around 55°F or lower. Place BWTs in suspected trouble spots, such as next to weedy or low areas, and use at least one BWT per 2 acres, or at least 8-10 BWTs per field in fields over 20 acres - the more traps, the better. Remove the BWTs from the soil after 10-14 days and inspect each of the corn seeds (whether germinated or not) for evidence of chewing damage. Also check for the presence of seedcorn maggots in the kernels, as well as any wireworms or white grubs feeding on or near the seeds. A field is considered at economic risk to these insects if an average of 5% or more chewed seeds per BWT is found. For more details on this method, please consult your local extension agent or pages 146-147 of the 2004 Pest Management Guide (PMG) for Field Crops. An alternative method for detecting the presence of wireworms and white grubs (but not seedcorn maggots because of their small size) in fields up to the day of planting are soil samples. Simply dig up a 1 ft2 by 6-inch deep amount of soil from several locations in a field and carefully inspect for the presence of these insects in the soil. If an average of 2 or more wireworms or white grubs, or any combination of the two are found, the field should be considered at economic risk. If treatment is warranted, the new seed-applied insecticides like Poncho 250 and Cruiser 5FS are effective. Also, the hopper-box treatment Kernel Guard continues to provide effective control of seedcorn maggot, wireworms, and white grubs (although the product does not claim to control white grubs). Consult the 2004 PMG for more information on insecticide controls measures for these pests.
Tomato Disease Update - Section 18 Label for Topsin
Christine Waldenmaier (ESAREC)
The EPA has granted a Section 18 registration again this year for Topsin M WSB fungicide manufactured by Cerexagri, Inc. for the control of white mold or timber rot (Sclerotinia sclerotiorum) in tomato. Topsin M WSB may be applied only by ground application at a maximum rate of 1 lb product per acre per application. A maximum of 4 applications per crop may be made at 7-14 day intervals not to exceed 3.5 lb per acre. Applications through irrigation are prohibited. The Pre-harvest interval is 2 days and worker reentry interval is 12 hours. This specific exemption will expire on September 30, 2004.
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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