CORN INSECT PEST UPDATE
(adapted from Maine Extension)
European Corn Borer pressure has been high in some but not all Vermont locations, and larvae continue to be found in some fields. A second generation of moths often occurs near the end of the season to threaten late corn. Corn in the pre-tassel stage or beyond should be sprayed for European corn borer when feeding damage is found on 15% or more of plants sampled in a field. Look for the larvae, damaged tassels and/or frass when scouting. On silking corn insecticide sprays are based on the number of corn borer moths caught in pheromone traps as well as feeding injury. Five or more moths caught per week in silking corn justify a spray, if fields are not being sprayed for earworm.
Corn Earworm is showing up in high numbers in many Northeast locations, especially along the sea coast. Spray frequency to protect silking corn is based upon the number of moths caught in the pheromone traps; more moths means more frequent sprays in order to get worm-free corn. Fields that do not yet have silking corn do not need to protect against corn earworm regardless of trap counts.
Fall Armyworm moths were caught in pheromone traps in most southern and coastal locations this week. Armyworm moths prefer to lay their eggs on young corn plants. When the eggs hatch the young larvae chew channels in the leaves between the veins. As they get older and larger the feeding holes become larger and ragged, often surrounded by masses of wet sawdust-like waste. When found, this injury is combined with any European corn borer injury to determine if protection is needed. Thresholds for spraying are 30% of plants infested in whorl stage corn or 15% for corn at pre-tassel and beyond. On silking corn, moths may lay eggs directly on flag leaves or husks, and the larvae may move into the ears without leaving visible feeding signs to be picked up when scouting. Therefore, if not spraying for earworm, and three or more fall armyworm moths were caught in a week, a spray would be recommended on all silking corn.
For insecticide options see your New England Pest Management Guide, or go to www.umassvegetable.org/grower_services/NEV_mgt_guide.html. Note that organic growers can use B.t. products (such as Dipel 2x or Xentari WDG) or spinosad (Entrust). The latter will be probably be more effective on corn earworm, but is more expensive.
For helpful images of these different corn insect pests in the moth and larval stages, see: http://www.hort.uconn.edu/ipm/veg/htms/cornpest.htm, and for comprehensive information on sweet corn production and pest management, order the Northeast Sweet Corn IPM Guide from: Communications Office, U-35, 1376 Storrs Rd., UCONN, Storrs, CT 06269-4035. (860) 486-3336. Cost is $19.50 plus $3.00 postage.
CHECK YOUR GARLIC BULBS!
If you have not yet pulled your garlic I suggest you check a dozen
or more bulbs for signs of
disease. With all the wet weather, I have been finding browning on the surface of bulbs at several farms, likely due to Fusarium basal rot. Mulched fields are probably more at risk. Even if the bulbs are not fully mature, they will not improved by leaving them in the soil if signs of disease are present. Pull them and dry them as soon as possible.
ITíS TIME TO TAKE SMALL FRUIT LEAF SAMPLES
Leaf analysis (also called tissue or foliar analysis) is an excellent means of monitoring plant nutrient levels. With perennial fruit crops, leaf analysis is even better than soil tests for determining an optimal fertilization program. While soil tests reveal the quantity of certain nutrients in the soil, leaf analysis shows exactly what the plant has succeeded in taking up. However, soil tests are necessary for determining soil pH and thus lime (or sulfur) recommendations. If nutritional problems are suspected in a given planting, it's a good idea to take both leaf and soil tests.
Leaf analysis is helpful for detecting nutrient deficiencies (especially of minor nutrients) before they effect plant health or yield. The best tissue analysis for berry crops comes from green, healthy, whole leaves. Do not submit plant tissue that has disease, leaf burn, insect or hail damage. Keep the material in a cool place (insulated chest) or refrigerate before mailing. Record all foliar sprays in case the results are influenced by nutrient or pesticide applications.
A minimum of 50 leaves from raspberries or strawberries, and 80 to 100 leaves from blueberries should be selected for each analysis. Do not mix leaves from fields with different soil types or management histories. Do not combine leaves from healthy plants with plants that are not growing well. Strawberry samples should be taken from the first fully-expanded leaves after renovation, about July 15 to August 15. Raspberry samples should be leaves from non-fruiting canes taken between August 1 and 20. Blueberry samples should be leaves taken during the first week of harvest, from July 15 to August 15.
Place samples in sealed paper bags, clearly labeled with field names. Include a note asking that results be sent to me so I can send you fertilizer recommendations. The cost is $20 per sample, make checks to: UVM Ag Testing Lab and mail along with sample to: Ag Testing Lab, Hills Building, Burlington VT 05405-0082, or deliver the sample in person during working hours. The Lab is on the third floor of Hills Building, just west of the water tower on the UVM campus. Call 1-800-244-6402 for more information.
GROWER FEEDBACK ON GREENHOUSE TOMATO MITE CONTROL
(Dave Chapman, Longwind Farm)
I have never found Amblesius fallacious to be an effective control of spider mite in tomatoes, even with heavy prophylactic releases before the spiders showed up. Phytoselius persimilis is the only thing that has worked, albeit rather poorly. If introduced immediately upon the mites' arrival, they will clean them up eventually, although not before the mites have spread to adjoining plants. The only way to survive without spraying seems to involve continuously chasing the mites with the Persimilis! It is expensive, but not as expensive as losing the crop. The idea seems to be that the Persimilis are not well adapted to the tomatoes, so it takes them several generations to get their mojo working. Even then they don't seem to be as mobile as the spider mites in tomatoes.
LATE BLIGHT ON POTATO AND TOMATO
(adapted from Cornell Extension)
Late blight has been confirmed in a variety of locations in NY and PA in tomato and potato so scout frequently. The best defense is protecting crops with fungicide on a regular spray interval of 5-7 days. In cloudy, humid weather viable spores of late blight can be carried many miles on the wind. Tomato and petunia transplants have brought it into NY in years past. It does not carry over in soil that we know of but does carry over on cull potatoes and volunteers. Fields at greatest risk are those where there is frequent and long-lasting rain, dew, fog or high relative humidity. In the morning while plants are wet with rain or dew late blight looks very black with spreading, irregular borders. A fine white fuzz of sporulation is often present. In the afternoon on a sunny day the lesions on leaves look brown with a prominent yellow-green border and the sporulation will be dried. Lesions may appear first on leaves, stems, the growing point, or in the axils of the leaves. Lesions may be tiny or may be over an inch across. If you think you may have late blight place green foliage with suspicious lesions in a blown-up plastic bag and seal. Get it to the UVM Plant Diagnostic Lab as soon as possible. Photos of this and many other vegetable diseases are at: http://vegetablemdonline.ppath.cornell.edu/cropindex.htm
For late blight control the more effective fungicides are Curzate, Gavel or Previcur Flex. Curzate and Previcur Flex need to be tank mixed with a protectant fungicide. Gavel is formulated as a mix with mancozeb. Bravo Weatherstik has also provided good control but itís not systemic and doesnít seem to have tuber blight activity. Maneb/mancozeb materials are good mixing partners. For organic growers, several fixed copper fungicides are available (Basicop, Champ, Kocide, etc.) and provide fair control of late blight and early blight, again if used preventatively. These and other copper products are registered for use on both potato and tomato. A good hill can protect tubers from late blight infection.
BERRY EXCELLENT NEWSLETTER ARTICLES ARE ON-LINE
An extensive collection of articles on cultural practices, insect, weed and disease pests and many other berry production issues, including color images, are available on-line at: http://www.nysaes.cornell.edu/pp/extension/tfabp/newslett.shtml
GET READY FOR FALL COVER CROPS
As your fields finish up with crops, be prepared to turn under crop residues and sow a cover crop as soon as you can. This will help improve soil quality by adding organic matter, reducing erosion, and even avoiding compaction from the force of raindrops, which can be significant. Options include crops that will winter-kill and be and to work in next spring such as annual ryegrass or oats. If you want to grow some of your own nitrogen sow 20 pounds of hairy vetch around the end of August, mixed with a bushel rye or oats. Let this grow until mid- to late-May next spring to get the most N out of it. For ideas on a variety of cover cropping options, including permanent beds, intercrops, no-till and spaders, order the video called Farmers and their Innovative Cover Cropping Techniques at: www.uvm.edu/vtvegandberry/Videos/videos.html
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