Eric Sideman's Pest Report
August 27, 2001
Crop Condition
It is even drier than last week as there has been only widely scattered showers that missed most areas of Maine. Crops that have not received water are stunted at best and in many cases dead. Those crops that are getting water are doing well and I am hearing reports of the best year ever from many growers. Insect and disease pressure is generally low except for a few issues mentioned below. Fall crops are ahead of schedule and many are ready to harvest now or soon (see the piece on squash below).Common armyworm
Although I have heard that the second generation moths are flying I have not heard of any larval activity. Let me know if you see any.Sweet corn
The earworms are not bad this year although some light catches do warrant an oil/Bt treatment of any fresh silking corn. Remember, if using oil/Bt, to wait until the time that the silk just begins to wilt. Too early and you will see poor tip fill. Of course, this year if you have not gotten water to the corn you will see very poorly filled ears anyway.The lack of storms and the resulting low numbers of earworms has been made up for by the European corn borer. The catches of these have been high for a while now and if you are harvesting corn that was not treated you are probably finding ECB anywhere on the ear. They will enter by way of the silk channel and also bore right into the side.
Bt sprays and oil/Bt treatment for ECB is still called for in any silking corn.
Squash and Pumpkin
Powdery mildew is widespread and many planting are already down from this. On the other hand, the squash yield looks very good and the maturity is way ahead of schedule. Here is a piece from the Massachusetts Vegetable Report:Pumpkins in many fields are starting to turn orange. If the current warm sunny weather continues, more and more fruit will color up in the next few weeks, well before peak market demand. Pumpkins may need to be held for several weeks before they can be marketed. There can be extra work involved in bringing fruit in early, especially for growers who normally have pick-your-own harvest, but we recommend that growers harvest as soon as the crop is mature and store under proper conditions, if it is feasible.
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 p dried up. If you need to leave pumpkins in field for pick-your-own, cut the handles from the vine to save them from advancing powdery mildew and reduce shrinkage.
As long as pumpkins are starting to turn color, they will ripen off the vine. 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 are healthy, storage in the field can be successful for a few weeks. If the vines die back, damage to the fruit from sun and insects is more likely. In any case, it is important to scout for insects feeding on the fruit, which may include squash bug nymphs or adults, or striped cucumber beetle. Control them if damage is evident. 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. 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 50 oF ) 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 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 on pallets or in pallet boxes. A period of curing can contribute to 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- 80 oF) 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. 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. Furthermore, any clean cuts during the curing period often 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 50 oF in the field and 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. 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 is kept as near to the temperature of the air as possible to avoid condensation which can lead to rot. Ideally, the storage environment should be kept at 50-55 F with a relative humidity of 50-70%. Low 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 the right conditions, sound disease-free pumpkins or squash fruit should have a storage life of 8-12 weeks or more. Even if it is difficult to provide 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.
--John Howell, Ruth Hazzard & Liz Maynard (Purdue)