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 MOFGA's 2006 Pest Reports - Compiled by Eric Sideman, PhD Minimize

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LOOKOUT: The early season pests are winding down and it is time to start scouting for some mid season pests that could wipe you out if you wait too long to respond. There have been reports of minor outbreaks of potato leaf hopper. You have to spot this pest early if you are to save your crop in years of large populations. Scout potatoes and beans for these flighty little critters by brushing the tops of the plants with your hands and looking for bunches flying up. Try to watch one land to verify the pest. European corn borers can be a major problem for potato and corn producers and they are out and laying eggs now. The eggs are laid on the foliage in a scale like pattern containing 15-35 eggs. The best way to monitor is to set up pheromone traps on your farm. If you do not do that you should visit the Extension website where they report the results of the traps they have set up around the state. For potatoes go to: http://www.mainepotatoipm.com/

And for sweet corn go to: http://www/umext.maine.edu/topics/pest.htm

Armyworm has been reported. No major outbreak, but growers should keep a close eye on their grain, corn, pasture, etc.


ASPARAGUS BEETLES: There are two different species, the common asparagus beetle and the spotted asparagus, beetle that occur here in the Northeast. Their life histories and damage is similar. It seems late for me to be talking about these critters because the horrible damage was done last month when the adults feeding on the new spears made them unmarketable. But now the larvae are feeding on the fern and eating of the leaves weakens the plant and reduces next years yields.  The adults of both species overwinter in crop residue. Cleaning up the residue in the fall is the main non chemical defense. The adults become active in the early spring and start feeding and laying eggs. The eggs hatch in just a week or two and the larvae of the common asparagus beetle feed on the leaves for three to four weeks and then drop to the ground and pupate. The larvae of the spotted one feeds on the berries. A second generation of adults may start the cycle over again and the next generation of adults will overwinter.  One cultural practice that would have helped is harvesting all the spears through the early spring and cutting them close to the ground. Asparagus is the only crop these beetles eat and so you potentially could starve out the overwintered adults by denying them anything to eat when they wake up. As mentioned above, cleaning up crop residue and debris near the bed in the late fall will deny them shelter for the winter. But now, if the population of larvae, which look like tiny gray slugs, is very large and destroying the ferns, you should spray with a botanical insecticide such as pyrethrum.
[Cutworms are still around and so I thought this great and in depth report by Ruth Hazzard from UMASS is important to see]


CUTWORMS ON SWEET CORN SEEDLINGS (Reprinted from a UMASS Vegetable Notes). Some growers are reporting serious cutworm damage in sweet corn that is at the seedling stage now. Cutworms can also damage in lettuce, brassicas, peppers, tomatoes, eggplants and other seedlings. On top of crops lost to flooding and soggy soils, this loss is especially discouraging. Corn is especially susceptible at the one to two leaf stage; by four to five leaves, cutworm feeding is not a problem.

Damage and identification. Feeding takes place at night. There may be some leaf feeding, but most often the stems are clipped. There are many species of cutworms that attack vegetables including black, variegated, dingy, spotted, dark-sided, or glassy cutworm. Spotted and variegated cutworms climb and feed above-ground, and black cutworms climb when they are young (less than half an inch long). Cutworms can be difficult to identify. Variegated cutworm has some pale yellow markings on its back, while black cutworm is nearly uniform gray to black with a greasy, rough appearance. (See Pest ID Supplement for photos). The cutworms we took from an infested sweet corn field this week were black cutworms, one of the most common in this area. Adults of all cutworms are moths with dark gray forewings, often with various lighter or darker markings, and lighter hindwings. They are in the same group of moths (noctuids) as the corn earworm, fall armyworm, and cabbage looper, but with very different life cycles and habits. Usually we don't see them since they fly at night. Moths are capable of migrating long distances. Black cutworm moths are reported to overwinter no farther north than Tennessee but migrate north very early in the season (March, April) and lay eggs. Thus, we see damage from their offspring in June. Some cutworms spend the winter in the larval stage as deep as 5 inches (12 cm) down in the soil and they may be present in the soil at planting time, ready to feed on early spring transplants and seedlings. Other cutworms winter in the pupal stage. Adults from these emerge in May or June. Moths emerge from pupae of spring-feeding larvae later in the season. There may be one to two generations per year.

Where are cutworms a problem? Cutworms occur where moths chose to lay eggs and where conditions are good for survival. Females lay eggs on grass leaves, weeds, or the crop residude. Attractive habitats include weedy or grassy areas, and alfalfa. Corn and soybeans are among the least attractive egg laying sites. Black cutworm moths are reported to select low spots in the field that has been waterlogged or flooded. We have had plenty of those type of areas this year! Eggs are also concentrated on low-lying weeds such as chickweed, curly dock, shepherd's purse, peppergrass, mustards such as yellow rocket, or plant residue from the previous year's crop. Note that the above list includes lots of winter annual weeds that grow in the fall - weeds that we often overlook. Larvae feed on weeds - and destruction of weeds just before planting can make the crop more vulnerable, since all other food has been just taken away from the existing population of larvae.

Monitoring. Pheromone traps can be used to monitor the adult flight. To sample cutworms, scout fields when seedlings are young to look for damage. Sample 50-100 plants in groups of 10 or 20. Larvae burrow in the soil and are difficult to find, though searching in the soil near a clipped stem usually turns up a cutworm. Estimate % stand loss to determine need for a spray. Damage may be more concentrated around field edges or in low areas.

Cultural Management. Weedy land harbors the most cutworms, as the adult moths seem to prefer dense plant cover for egg laying. Crop residues may also attract higher populations. Therefore, crops that follow weedy crops, alfalfa, or no-till crops are more likely to be damaged by cutworms. Plant early transplants into fields that had low weed pressure the previous year, especially in the fall, or where crop residue was tilled under in the fall. There seems to be little information about specific relationships between what cover crops are planted in the fall, and cutworm infestations in the following year. Plow fields in spring and keep weed free for at least two weeks before planting to starve young larvae and reduce egg-laying. Avoid planting susceptible crops close to sod, alfalfa or fallow areas. Summer plowing disturbs eggs and larvae and raises them to the soil surface where they are more vulnerable to predation and desiccation. Fall plowing will do the same. Plan rotations to avoid planting vulnerable crops after a grassy sod, and plow sod fields in later summer or early fall. Cultivate frequently to injure and expose hiding cutworms to predators.

Organic options. Insecticide baits made of a concentrated solution of an allowed insecticide, mixed with bran and a bit of molasses have been reported to work. The bait can be sprinkled on the ground near the crops or made into patties that are placed along the rows. Bt sprays (ie, Bt aizawi or kurstaki directed at plant stems and foliage) work sometimes, but not consistently, possibly because large cutworms do not ingest a big enough dose of BT to stop feeding and die before they have caused damage. Collars around each seedling work on a garden scale but are impractical for field scale crop systems. Daily search and destroy missions -- by hand -- are a time-honored "biological" management for small plantings!

Biological management. Probably the most promising biocontrol organisms are beneficial nematodaes, which are available commercially and can attack soil insects such as cutworms. It is important to use the correct species. Two species of nematodes, Steinernema carpocapsae (Sc), or Heterorhabditis bacteriophora (Hb) are often used in combination because they attack insects in different levels of the soil. This works well for cutworms that move up and down. The nematodes are shipped to you on a sponge. You mix them with water and apply to the soil. Follow the instructions that come with them. They can reduce cutworms and last for anywhere from 8 days to several weeks, according to various research trials. The nematodes reproduce in the soil and, if the conditions are good for them, large populations of the nematodes will build up and these will hold the population of cutworms down. Good soil moisture favors survival. Repeat applications may be needed. -Ruth Hazzard (with thanks to the following sources: Capinera, Handbook of Vegetable Pests; Vern Grubinger (UVM), Brian Caldwell (NYS-NOFA),Eric Sideman(MOFGA), Rex Dufour (ATTRA)) Updated June 2006)


BACTERIAL SPOT AND BACTERIAL SPECK OF TOMATO AND PEPPER:

Bacterial spot caused by Xanthomonas campestris pv. vesicatora (Xcv) is present wherever tomato and peppers are grown. In general, Xanthomonas pathovars have narrow host ranges. Xcv consists of different strains that vary in their pathogenicity to tomato, pepper, and nightshade. The bacterium is able to survive on tomato volunteers and can overwinter in diseased plant debris. Seed is an important mechanism for survival and dissemination of Xcv. Disease development is favored by temperatures between 80 and 90 degrees F and by heavy rainfall. The bacterium is spread by wind-driven rain, workers, farm machinery, and aerosols. It penetrates through stomates and wounds created by insects, wind-driven sand, and tools. Xcv affects all above-ground plant parts. On leaves, the spots are generally brown, circular, and water-soaked. Bacterial spot lesions do not have concentric zones or a prominent halo. When conditions are optimal for disease development, spots can coalesce to form long, dark streaks. A general yellowing may appear on foliage with many lesions giving the plants a scorched appearance, and the plants may exhibit severe epinasty. Only green tomato fruit is susceptible to infection and lesions are quite distinct, beginning as minute, slightly raised blisters with a halo that resemble the birds-eye spot caused by Clavibacter michiganense (bacterial canker). As lesions enlarge, they loose their halo and become brown, raised, and scab-like. Lesions on ripe pepper fruit may be scab-like or sunken.

Bacterial Speck of Tomato: Bacterial speck occurs on tomato not pepper. It is a cosmopolitan disease, generally of minor concern in New England, favored by low temperatures and high moisture. The bacterium Pseudomonas syringae pv tomato causes a fruit spot and foliage blight. This bacterium is also seedborne, spreads within fields in the same manner as bacterial spot, and may persist in weed species. Lesions on leaves are round and dark brown to black with a halo that develops with time. Spots may coalesce, killing large areas of tissue. On fruit, small (1/16 inch), dark spots or specks develop with the tissue around them often more intensely green than unaffected areas.

Management of Bacterial Spot and Bacterial Speck: Although the two bacteria are unrelated, their life histories and management strategies are similar.
1. Buy certified seed from a reputable source or use seed treatments to reduce transmission.
2. Produce disease-free transplants by raising transplants in an area where production does not occur. Inspect all purchased transplants carefully and if transplants originate in southern states they should be certified.
3. Rotate fields to avoid carry-over on volunteers or crop residue.
4. Keep fields free from volunteers, weeds, and cull piles.
5. Avoid working in fields when bacterial diseases are present and the fields are wet.
6. Apply appropriate bactericides or combination pesticides. In general, bacterial diseases of field crops are difficult to control with pesticides; copper/mancozeb solutions are most effective When a significant amount of disease is present, pesticides are usually not effective.

Chemical recommendations: There is not much for the organic grower except copper hydroxide (Champion WP): 4 tbs/1000 sq ft ( 0 dh, REI 24 h). Greenhouse and Shade house crops. Begin applications when disease first threatens and repeat at 7-10 day intervals as needed. Do not apply in a spray solution with pH less than 6.0 or phytotoxicity can occur. --(modified from a report by M. Bess Dicklow. In UMASS Vegetable Notes)


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