MOFGA Pest Report 2005
30 June

(View List Of All 2005 Pest Reports)

CROP CONDITIONS are widely variable from farm to farm. The cold, wet period early in the season stunted growth, rotted seed, washed away soluble nitrogen, stymied any biological activity so natural sources of nitrogen typically used by organic growers did not decompose and release crop-available-nitrogen, and in many cases kept wet fields anaerobic which facilitated the loss of nitrogen to the air as gases. In addition, the wet weather and soaked fields set many farmers way back and kept farmers out of fields where they should have been cultivating. So, now what I see are some farms who had lucky timing and well drained soils with some good looking crops, but many farms with stunted, off color crops beleaguered by weeds who are robbing the bit of nitrogen left after the deluge. And on top of this, the very hot weather and summer sun are stressing plants that have not developed adequate roots yet, and the cucumber beetle populations are large on most farms and the Colorado potato beetle eggs are hatching (both pests covered in the June 14, 2005 Pest Report).

But now the growing conditions are very good with plenty of moisture and lots of warmth.

IMPORTANT POTATO NOTE :

KNOW WHERE YOUR POTATO SEED COMES FROM BECAUSE SEED FROM CERTAIN STATES IS NOT ALLOWED IN MAINE (***This applies to gardeners as well as farmers***)

Columbia Root Knot Nematode (CRKN) Meloidogyne chitwoodi is a major economic pest on potato in the Pacific Northwest. It is well adapted to cool soil temperatures, where it can develop at 6 degrees Celsius (43 degrees Farenheight). Pimple-like galls can be produced on the tuber surface, depending on the cultivar (see this Canadian Food Inspection web page, or whole Google Image search for images). When galls are produced, they appear as small, raised lumps above the developing nematodes, giving the skin a rough appearance. Galls may be grouped in a single area or scattered near the tuber eyes. As a result of the separation of this species of nematode from other root knot nematodes, a number of states and Canada established quarantines on areas known to be infested with CRKN. Maine established its quarantine in 1982 (Code of Maine Regulations, 01-001, Chapter 30). Our quarantine prohibits the importation of all articles that could introduce CRKN into the state (such as seed potatoes, processing potatoes that are unwashed, used implements, etc.) from all areas known to be infested with the nematode. The areas currently included in Maine's quarantine are "the states of Oregon, Washington and Idaho; the county of Humboldt of the State of Nevada; the counties of Siskiyou and Modoc of the State of California; the county of Rio Grande of the State of Colorado; the county of Iron of the State of Utah; the county of Westmoreland in Virginia" (from the quarantine). The quarantine is designed to keep Maine free of CRKN, not only to prevent losses to potatoes from this pest, but also to prevent Maine from being quarantined by other states and Canada and losing markets for sale of our seed potatoes if we are found to have the nematode in our soils.

GREENHOUSE TOMATO REPORT

(adapted from Quebec web site by Rebecca Nixon, Old Athens Farm, reprinted from Vern Grubingers Vermont Vegetable and Berry News)

During hot weather remember to irrigate properly. The main cooling mechanism for tomato plants is evapo-transpiration. Keep your humidity at 70%. If it is not too hot you can do this by venting less. The plants will keep the temperature down 2 to 3 degrees in your greenhouse through evapo-transpiration. If the temperature hits 80 degrees F, you will have to compromise with the humidity and ventilate. It can't get too hot. If you have good vigorous plants the fruit should set nicely with the sun and heat. The trusses should be short, strong, and grow from the stem at a 60 to 90 degree angle. Weak plants will make long thin (vegetative) trusses. Your fruit quality will suffer on these trusses. Unfortunately the cloudy May helped give us a lot of these trusses.

In hot weather you can keep the greenhouse opened up 24 hours a day but with stagnant air the plants will not recuperate overnight. The temperature can go as low as 53 degrees F. If you are able, start heating at 4am to avoid condensation. Don't let the sun warm up your greenhouse since you want an ‘active’ environment as soon as sunlight is available.

Blotchy fruit and uneven ripening can be caused by the following: Lack of potassium at the fruit caused by plants that are not transpiring enough; a cold climate in the greenhouse when the fruit are ripening; vegetative plants; too large a fruit load; low light.

DOWNY MILDEW IS MOVING NORTHWARD: BE ALERT FOR SYMPTOMS

Downy mildew of cucurbits typically has been a minor problem in New England because it usually arrives very late in the season if at all. Last year it hit the mid-Atlantic states, New York and New England early enough to cause serious crop loss. This year, it has once again made its way northward (New Jersey) earlier than usual. This is a much more destructive disease than powdery mildew. It was confirmed in 10 acres of pickling and slicing cucumber (cvs. Jackson Supreme and Speedway) on June 13, 2005 in Cumberland County, New Jersey. These were cucumber transplants that originated in Florida. No downy mildew was found on other nearby cucurbits (yellow squash, zucchini and watermelon) which were also purchased as transplants from Florida. Virtually all cucumber plants in the field are infected and symptoms are currently confined to the older leaves. This field is fairly isolated from other cucumber plantings. No downy mildew was detected in three nearby cucumber fields.

Downy mildew overwinters in warmer climates. It produces spores that can be carried north on storms and wind currents. Thunderstorms from the south deposit those spores on our vine crops, and if conditions are right for disease, it can cause significant damage and loss. Thus, the threat to crops in our area depends on several factors. One is where the disease has currently been found. Second is how likely it is that spores will move into the area, which depends on movement of wind currents. Then it depends on whether local conditions that favor deposition and survival of the spores. Rainfall deposits spores, hence rain increases risk. Sunlight kills the spores, so it reduces risk. Cloudy conditions favor the disease. All of this is explained on the website listed below. The North Amercian Plant Disease Forecast Center, based at the North Carolina State University, provides twice weekly updates on where downy mildew has been reported and what its expected trajectory is. Tobacco growers are familiar with this website, which also tracks blue mold and soybean rust. The latest forecast was issued on June 21 and can be viewed at http://www.ces.ncsu.edu/depts/pp/cucurbit/ and clicking on "Current Forecasts" then on "Cumberland County, NJ" at the bottom of the page. No new occurrences have been reported since June 13. There is a lot of good information about downy mildew and other cucurbit diseases on this website, including a 2005 fungicide efficacy table for all cucurbit diseases, at http://ipm.ncsu.edu/agchem/chptr6/615.pdf

We certainly hope that weather conditions will not favor the disease and it will not move it further northward. However, it is very possible that downy mildew will come into New England early again this year. We need growers to be on the lookout for it. Scout your fields regularly. Leaf symptoms can be used to diagnose downy mildew in the field in most cases. On cucurbits other than watermelon, small yellowish areas occur on the upper leaf surface. Later, a more brilliant yellow coloration occurs with the internal part of the lesion turning brown. Usually the spots will be angular as they are somewhat restricted by the small leaf veins. When the leaves are wet, a downy white-gray-light blue fungus growth can be seen on the underside of individual spots (lesions). On watermelons, yellow leaf spots may be angular or non-angular, and they will later turn brown to black in color. For good pictures go to this North Carolina State University web page. Often on watermelons, an exaggerated upward leaf curling will occur. If you suspect downy mildew, call the diagnostic lab (Bruce Watt 1800 287 0279) and send a sample. It is easy to confuse it with powdery mildew or other diseases. Organic growers have few options for fungicides. Efficacy studies with copper compounds have shown one poor result in recent studies and four good and three poor results against different species of downy mildew on other crops.

--(Reprinted with minor changes from UMASS Vegetable Newsletter, by R Hazzard, with thanks to the following sources: Robert. Wick, UMass Amherst Plant Pathologist; John Mishanec, Cornell Coop. Extension Service; Gerald Holmes, Extension Plant Pathologist, NC State U

Sweet Corn IPM Newsletter

(Modified for organic growers from the Umaine Newsletter by David Handley)

No. 1 June 24, 2005

2005 Sweet Corn Pest Season Begins!

A Very Cool, Wet Spring = A Slow Start for Plants and Insects

This year's University of Maine Cooperative Extension integrated pest management (IPM) program for sweet corn is getting underway. More than twenty volunteer farms are serving as pest monitoring and demonstration sites this year. Farm locations include North Berwick, Wells, Dayton, Cape Elizabeth, New Gloucester, Poland Spring, Auburn, Lewiston, Dresden, Jefferson, Nobleboro, Warren, Monmouth, Wayne, Oxford, Farmington, Levant, Stillwater, Garland and East Corinth. Pheromone traps are being set up at these locations to monitor the adult (moth) stages of European corn borer, corn earworm and fall armyworm. Fields at these farms will also be scouted for feeding injury by the larvae of these insects. Management recommendations will be based on the information we collect and will be updated weekly. Our results will be passed on to you through this newsletter every week for the remainder of the season. If you would prefer to receive this message via e-mail, give us a call at 933-2100 or send an e-mail message to: dhandley@umext.maine.edu. If you no longer wish to receive this newsletter, or know of someone who would like to be added to the mailing list, call us at (207) 933-2100. The information will also be placed on the Pest Management Office web site at: http://www.umext.maine.edu/topics/pest.htm.

SITUATION
Very wet conditions have delayed planting in most fields and delayed growth in fields that were planted. Early corn planted under plastic mulch or rowcovers is now approaching late whorl to pre-tassel in southern Maine, while uncovered early fields are struggling into the whorl stage. Some fields are only now becoming dry enough to plant, but it may be too late to mature any thing other than short season varieties. Expect the supply to be spotty this season, and plan and price accordingly. Weed management may become an issue in some fields as herbicides applied earlier may have leached away. Nitrogen deficiency may also become an issue, and growers should be ready to sidedress to compensate.

European Corn Borer: Pheromone trap catches indicate that we are experiencing a significant emergence of European corn borer moths. These moths will be laying eggs on corn plants and we expect to soon find larvae feeding on the foliage. European corn borer is the only one of the three major insect pests of corn that can successfully overwinter in Maine, and it is usually the first pest to become a significant problem. To monitor corn borer, we typically scout 100 corn plants in each field, examining twenty plants in a row at five locations in the field. This sample provides a reasonably accurate estimate of the total amount of injury in a field. In the early stages, European corn borer feeding damage looks like small "pinholes" in the leaves. Corn in the whorl stage need only be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field. Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15%. This is because larvae feeding on the later stages are more likely to move into the ears of the plant. Sprays during the pre-tassel stage when both moths and larvae are present will reduce the opportunity for larvae to move into the stalks and ears of the plant, where they are protected from sprays. Good spray coverage of the plant provides the most effective kill of larvae as they move from one part of the plant to another. Rotating the type of insecticide used may also improve control. Materials now registered for controlling European corn borer include Bacillus thuringiensis (OMRI listed Bt products include, Javeline, Dipel 2X and DF, Agree) and Entrust. When corn reaches the silk stage sprays may be based on the number of corn borer moths caught in pheromone traps rather than just feeding injury. European corn borer moths will lay eggs on flag leaves of silking corn and the larvae can move into the ears without leaving any visible feeding injury that would be noticed when scouting. Therefore, if more than five moths are caught in a week in a field with silking corn, a spray will be recommended.

NOTE: Here is the situation reported today (June 30) in the most recent Sweet Corn IPM Newsletter;

European Corn Borer: Pheromone trap catches of European corn borer moths generally increased this week, indicating the continued emergence of the first generation of this pest. These moths are laying eggs on corn plants and we are beginning to find larvae feeding on corn foliage. Now is the time to start scouting fields for European corn borer injury. We recommend scouting 100 corn plants in each field, examining twenty plants in a row at five locations in the field. This sample provides a good estimate of the total amount of injury in a field. In the early stages, feeding damage looks like small "pinholes" in the leaves. Corn in the whorl stage need only be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field. Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15%. Remember that the pre-tassel stage offers a good opportunity to control larvae, because this is often when they are exposed, moving from one part of the plant to another. Good spray coverage is critical for getting to the most effective control.

When corn reaches the silk stage sprays can be based on the number of corn borer moths caught in pheromone traps rather than just feeding injury. European corn borer moths will lay eggs on flag leaves of silking corn and the larvae can move into the ears without leaving any visible feeding injury that would be noticed when scouting. Therefore, if more than five moths are caught in pheromone traps in a week in a field with silking corn, a spray is recommended. This week feeding injury exceeded the control threshold only in one field in Oxford, but we expect most fields to be showing more injury soon. A spray was recommended for silking fields in Dayton and New Gloucester, where pheromone trap counts were over the five moth threshold.

Corn Earworm: Pheromone traps are now being set up around the state to monitor the arrival of corn earworm. Corn earworm generally appears in Maine around the second week of July, but the actual date varies greatly. The arrival of this pest is only a concern for fields with corn in the silk stage. Fields not yet in silk do not need to be protected from corn earworm. When corn earworm moths start being caught at a site, all silking corn in the fields should be protected with a spray. These moths lay eggs on the fresh silks and the larvae move directly into the ears of corn. When corn earworm moths cannot find silking corn to deposit their eggs on they may lay eggs on the leaves of younger corn. The larvae will feed on the foliage and tassels, similar to armyworm, until the ears become available. When larvae are found feeding on younger corn, the damage is accounted for along with any borer or armyworm damage to determine if a spray is warranted. We will be watching our traps closely to keep you informed as the situation changes.

Fall Armyworm: This is usually the last serious corn insect pest to arrive in Maine. The moths must fly in from southern overwintering sites, and tend to lay their eggs on the youngest corn available. When the larvae hatch, they chew large, ragged holes in the leaves, and may bore into developing ears. We will be setting up fall armyworm pheromone traps at our sites over the next couple of weeks.

Other Pests of Note:
Common Armyworm is often found chewing on early corn. Like fall armyworm, this caterpillar chews large holes in young corn. The larvae are light brown with yellow and black stripes running along the body. This insect is usually only present early in the season and the corn can often outgrow the injury. However, heavy infestations may require control. In general, when these pests cause significant injury in a field, we count the injury along with European corn borer damage. So, if damage from these pests, plus the injury from corn borer exceeds 30% of whorl stage plants or 15% of pre-tassel plants, we would recommend a spray to control them.

Common Stalk Borer: This pest can be a problem early in the season, but usually only around the edges of fields. The injury is similar to European corn borer, but the feeding holes are larger. The larvae are purple colored with white stripes. If high numbers of stalk borer are found in pre-tassel stage corn within the field (not just along the edges) include the injury with corn borer to determine if a control is needed.

Cutworms: Cutworms can pose a threat to early cornfields, but this pest tends to be more of a problem on field corn. The larvae feed at night and cut off young corn plants at ground level. When present in high numbers, they can devastate a cornfield in a single evening. (see cutworm discussions in earlier pest reports).

Nitrogen Sidedressing?
Are you looking for a way to reduce input cost and maintain your productivity? In season soil nitrate testing can help you manage your nitrogen fertilizer efficiency. Research has documented that growers typically over apply N fertilizer. This year we have received a grant from Sustainable Agriculture, Research and Education (SARE) to demonstrate the use of pre-sidedress nitrogen testing (PSNT) at volunteer farms in Maine. This test helps determine the amount of available nitrogen in the soil just as the plants demands for nitrogen increase (8 to 12 inches tall). It accounts for nitrogen from soil reserves, such as organic matter, cover crop residues and previous manure applications. The PSNT can save money by showing fields that do not need sidedressing because they already have adequate nitrogen. If you are interested in having a PSNT done in your field, please give us a call at 933-2100 and we will try to accommodate you. We need to carry out the test when the corn is 8-10 inches tall, so please give us enough lead-time. The results of the test take about 48 hours.

Do-It-Yourself IPM: To get the most accurate information about the pest situation on your farm you should monitor the fields yourself on a regular basis. Pheromone traps and lures are available that can give you an accurate, early warning of the arrival of all of the major insect pests. Pheromone traps and lures can be purchased from pest management supply companies such as Gempler's in Mt. Horeb, Wisconsin (1-800-382-8473) or Great Lakes IPM in Vestaburg, Michigan (517-268-5693).

To learn more about IPM scouting techniques, insect identification and control thresholds, order the fact sheet Managing Insect Pests of Sweet Corn available from the University of Maine Cooperative Extension. Color pictures are provided to help with insect identification, and a chart with spray thresholds is supplied to post near your sprayer for easy reference. For copies of this free publication contact the Pest Management Office at 1- 800-287-0279.

IPM Web Pages:
http://www.umext.maine.edu/topics/pest.htm
http://pronewengland.org/ http://www.pestwatch..psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/
http://www.nysipm.cornell.edu/vegetables.html

Sincerely,

David T. Handley Vegetable & Small Fruit Specialist

Highmoor Farm Pest Management Office
P.O. Box 179 491 College Ave
Monmouth, ME 04259 Orono, ME 04473
(207) 933-2100 1-800-287-0279

Where brand names or company names are used it is for the reader's information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

A Member of the University of Maine System.

(About the Pest Report author: Eric is MOFGA’s Technical Services Director, essentially an organic "extension agent". He can be reached at the MOFGA office to answer your questions about farming and gardening. Link to MOFGA Contact Page, or email Eric directly.)