Eric Sideman's Pest Report
September 1, 2003

(View List Of All 2003 Pest Reports)

We are nearing the end of the season for Pest Reports. There are still a few things happening out there that you may be able to manage and some late season management practices that will show their benefits next season.

HORNWORMS

PHYTOPHTHORA BLIGHT

-- modified from report by R. Wick and R. Hazzard, University of Massachusetts

CERCOSPORA LEAF SPOT ON BEET, SWISS CHARD, AND SPINACH

Extended periods of nighttime temperatures between 70-80 °F and relative humidity of 90-100% favor disease development. Occurrence of the disease is negligible when temperatures are below 61 °F.

Because the fungus survives on crop residue infected fields should be deep-plowed and planted on a 2-3 year rotation with non-host crops. New fields should be separated from recently planted fields by a minimum of 300 feet. Resistant cultivars of sugar beet only are currently available. --C. Bergweiler, Extension Vegetable Program and R. Wick, Plant Disease Diagnostic Lab

SWEET CORN

Situation: Maine season corn is finishing up in most of the state and few of us still have fresh silking corn that needs attention. But, peppers may still need attention (see below) Quality of corn has been very good for the most part and prices have remained relatively stable. I have had very good results with the ZeaLater using either Bt or Spinosad (NOTE: come to the MOFGA/Extension Farmer to Farmer Conference in Bar Harbor on November 1&2 to here about it). Cooler weather patterns have kept moths counts down in most locations, especially corn earworm, but fall armyworm and a second generation of European corn borer continue to pose a significant threat to late corn. We have started taking down our traps from farms where corn is beyond the stage of susceptibility to most pests, and will only be visiting the remaining farms once per week until the end of the season.

European Corn Borer: Pheromone trap catches of moths continue to be high in many locations. This apparent second generation of corn borer is now the major threat to silking corn in many fields where corn earworm populations have dropped below threshold levels (at least for the moment). Sprays for European corn borer to protect silking corn were recommended in nearly all locations this week as few fields with silking corn required sprays for corn earworm. Fresh European corn borer feeding damage exceeded the threshold in some fields, and this injury is increasing as the second generation gets established.

Corn Earworm: Corn earworm moth numbers dropped dramatically in many locations this week, as cooler temperatures and weather patterns from the north slowed their activity. Many fields required no regular spray interval for silking corn and those that had a few moths were extended to 5 or 6 day spray schedules. This may only be a temporary lull in corn earworm pressure. Late season tropical storms can often bring up corn earworm moths to infest late corn. Keep a close eye on the weather.

Fall Armyworm: Fall armyworm moth trap catches were generally lower this week, although the threshold of three moths per week in silking corn was again exceeded in about half of the fields scouted. All of these sites also required protection from European corn borer as well. Armyworm feeding continues to be significant in most pre-silking fields. When found, this injury is combined with any European corn borer injury to determine if protection is needed. The control threshold is 15% for corn at pre-tassel and beyond.

PEPPERS

This should serve as an alert for pepper growers. While many farms report that they do not have much of a problem with borer in peppers, it would be advisable to take precautions to protect pepper fruit unless captures have remained below 7-10 ECB moths per week at your farm. It has been three to four weeks since the second flight began, which means that there has been time for eggs to be laid and hatch. In pepper, the small flat white egg masses are laid on the undersides of leaves. When the tiny borers hatch, they do a small amount of feeding on leaves, but move quite quickly into the fruit. Larvae enter fruit by boring through the pepper under the calyx. A small amount of dried frass that looks like a bit of sawdust near the calyx is the only sign of entry. Opening the fruit will show feeding damage in the placenta area. Worms in corn are bad, but worms in peppers are even worse. The entry hole may also provide entry for soft rot pathogens, and this may be the most visible damage that you see. If fruit sinks in the wash tank, it is probably infested with borer.

If you believe that this may be a significant problem for you, maintain a regular spray schedule on peppers while the flight remains high. Spinosad (Entrust) should work Bt products should should too and should be sprayed twice weekly.

If you find that one pick is infested and you have younger fruit in the field, it is probably worthwhile to start a spray program to protect the younger fruit as it matures. ECB enter fruit that is one inch in diameter or larger.

(modified from Mass. Veg. Newsletter)

POTATO AND TOMATO

Late blight only grows on living plant tissue. If your potato plants are already fully down, they won't be infected, so no sprays are needed. If you have a decent crop and some live tissue above the ground, an alternative to spraying copper would be to mow and flame the tops to kill them fully.

modified from a report by Brian Caldwell
Farm Education Coordinator
Northeast Organic Farming Association of New York

PUMPKIN AND WINTER SQUASH HARVEST AND STORAGE

Attention to curing and handling will go a long way toward improving the life of winter squash and pumpkin fruit. In fields where pumpkins are turning orange, it is worthwhile to cut and windrow the pumpkins and bring them in out of the field. This will allow the handles to cure and will protect fruit from insects, vertebrate pests, and diseases. Pumpkins are not marketable if the handle is broken off or dried up. If you need to leave pumpkins in the field for pick-your-own, cut the handles from the vine to save them from advancing powdery mildew and reduce shrinkage. On some varieties, however, handles shrink after cutting. Ideally, if the timing is right, pumpkins would be cut one to two weeks prior to marketing.

Ideally, pumpkins should be harvested when fully mature, with a deep orange color and hardened rind. However, as long as pumpkins have started to turn color, they will ripen off the vine if held under the proper conditions. While not ideal, this may be preferable to leaving them in the field if conditions are not favorable. If necessary, pumpkins can be ripened in a well-ventilated barn or greenhouse. The best temperatures for ripening are in the seventies or even low eighties during the day. Night temperatures should not drop below the sixties. In a greenhouse, temperature can be managed with ventilation on sunny days. Unless it is quite cool, heat is not likely to be needed if the house is closed up at night.

Often it is not feasible to harvest pumpkins early and store them until they can be marketed, and so they must be 'stored' in the field. If vines and fruit are healthy, storage in the field can be successful for a few weeks. If the vines die back, damage to the fruit from sun, disease and insects is more likely. In any case, it is important to scout for insects feeding on the fruit and handles, which may include squash bug nymphs or adults, or striped cucumber beetle. Control them with insecticides if damage is evident - look at fruit throughout the field to assess feeding damage on handles and fruits. Squash bug nymphs are gray with black legs and usually group together on the undersides of leaves. Adults are a dull brown and are more likely to feed singly. Cucumber beetles at this time of year are most likely found in flowers, but may also group together on fruit. Both cause unsightly scarring and pitting which can also allow entry of diseases. There is no set threshold, but judge the level of damage and the proportion of fruit with damage. In fields that have a history of Phytophthora blight, Fusarium fruit rot, or black rot, field storage may increase the incidence of these problems, particularly if we have a period of wet weather or a major storm while fruit is sitting in the field. This has been one of the causes of significant losses in recent years, and one reason that we recommend bringing fruit in as soon as it is mature.

Winter squash is also maturing in some fields. Fruit that are free from disease and haven't been subject to much chilling (below 50ºF ) should be selected for long-term storage. Sorting fruit in this manner requires extra labor and may not be economical, but it should not be too difficult to separate bins of squash according to good and poor fields or areas of fields. Fruit from fields where Phythophthora is present are not the best choice for storage.

Storage life depends on the condition of the crop when it comes in and your ability to provide careful handling and a proper storage environment. All fruit placed in storage should be free of disease, decay, insects, and unhealed wounds. When harvesting squash and pumpkins, it is important to handle the fruit with care to avoid bruising or cutting the skin. Despite its tough appearance, squash and pumpkin fruit are easily damaged. The rind is the fruit's only source of protection. Once that rind is bruised or punctured, decay organisms will invade and quickly break it down. Place fruit gently in containers and move bins on pallets. Removal of the stem from squash (butternut, Hubbard, etc.) will also decrease the amount of fruit spoilage because the stems frequently puncture adjacent fruit, facilitating infection.

A period of curing after harvest can help extend storage life. This may be done in windrows in the field -- especially with a series of warm, dry days -- or by placing squash in a warm dry atmosphere (70-80ºF) with good air circulation, such as a greenhouse, for up to two weeks. This pre-storage treatment permits rapid drying of the outer cell layers, and when combined with a dry atmosphere for storage inhibits infections that can take place at this time. Any clean cuts during harvest a likely to heal over and are no longer a source for injury or infection.

Take care to avoid subjecting squash to chilling injury. Chilling hours accumulate when squash is exposed to temperatures below 50ºF in the field or in storage. Injury increases as temperature decreases and/or length of chilling time increases. Chilling injury is of particular concern with squash intended for storage because it increases the likelihood of breakdown. If squash has been exposed to chilling injury it should be marketed first and not selected for long-term storage. Remove squash from the field if temperatures likely to drop below fifty degrees for any length of time.

After curing, move squash or pumpkins to a dry, well-ventilated storage area. Pressure bruises can also reduce storage life, so avoid rough handling, tight packing, or piling fruit too high. Fruit temperature should be kept as close to the temperature of the air as possible to avoid condensation, which can lead to rot. Ideally, the storage environment should be kept at 55-60ºF with a relative humidity of 50-70%. Lower relative humidity increases water loss, resulting in reduced weight, and if excessive, shriveling of fruit. High relative humidity provides a favorable environment for fungal and bacterial decay organisms. Under ideal conditions, disease-free pumpkins should have a storage life of 8-12 weeks and butternut squash up to three or four months. Even if it is difficult to provide the ideal conditions, storage in a shady, dry location, with fruit off the ground or the floor, is preferable to leaving fruit out in the field.

As you plan for storage and marketing, keep in mind that the market for pumpkins seems to get earlier every year. Fall decorative displays include pumpkins, and those displays begin showing up as Labor Day approaches. One of the best solutions to early-maturing pumpkins may be finding an early market. With so many late-planted field this year, early pumpkins are likely to be in demand.

--J. Howell, R. Hazzard, A. Carter, University of Massachusetts.
Additional resource: Liz Maynard (Purdue)

(About the 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.)