Pest Message for August 25, 1999

We are nearing the end of the season and I plan to make these messages even less regular. I plan to keep them going until early October but less than a weekly basis that I have aimed for over the summer.

Remember to thank all my sources for info if you run into them including Dave Handley and Jim Dwyer from U Maine Extension, Ruth Hazzard and Sonia Schoelmann from U Mass Extension, Vern Grubinger from Vermont Extension, Clay Kirby from the Pest Management Office and the MOFGA certified growers who take the time to send me reports from the field. Please send along anything interesting you note in your fields.

CROP CONDITION

The rain we have received recently has really made some crops jump. Pastures are growing again. Of course it is really too late for many markets but it has saved some growers. For others crop losses this year are significant, and many growers are discouraged. However, there is still plenty of high quality local food available at farmers markets and farmstands—and it is important to give the public the message that they will have fresh local food to look for now and throughout the fall!

There are no new pests around that were not reported in previous messages but there are plenty of things to keep an eye on if good harvests are to continue and fall harvests are to be plentiful and healthy.

EARLY PUMPKINS

Pumpkins are ripening early in most locations, and growers are wondering what, if anything, to do about it. The concern is that the pumpkin fruit may not hold up long enough for fall sales. The longer they sit in the field, the greater the opportunity there is for wildlife damage, especially deer and woodchucks, and infection of the fruit and handles by disease, especially if nothing was done to control powdery mildew earlier. Powdery Mildew is showing up throughout the state on cucurbits. (PM infection can increase susceptibility to diseases that cause pumpkin and squash handles to rot in storage. Protective sprays are usually necessary to control PM into the latter part of the growing season.

Many vine crops are showing browning of leaves.

According to Dr. Tom Zitter at Cornell, much of this is due to heat stress.

Older leaves in the center of the plant will show this stress first. Another cucurbit disease, Phytophthera, has spread rapidly on a farm in Essex, Vt. destroying an entire pumpkin field.

The potential for these problems can be reduced by harvesting the ripe fruit and putting it in a sheltered area, ideally a barn. This would require placing the fruit in bins and care must be used to avoid any injury that can lead to infection by disease, which could be worse than leaving them in the field. Before harvesting, fruit should be fully mature and cured so the skin will be as hard as possible. One grower noted that he had a rat problem when he has done this in the past.

Obviously this is not a good option for many growers. It certainly is not for pick-your-own pumpkins and many growers don’t have enough room in a building for them. A greenhouse with the sides rolled up may do in a pinch, but would probably be too warm during the day. Pumpkins could be placed in bins, covered on top and left outside. This should protect from wildlife and disease.

The only option for many growers, especially pick-your-own growers, is to leave them in the field and hope for the best. In this case, it may be a good idea to cut the stems as they would be in harvesting. This will help prevent disease from entering the handle as the vines decay.

Another idea is to have an early display of pumpkins at the farm stand. This might attract more business, although one grower expressed the concern that she didn’t want customers to start thinking "Fall" just yet when she still had lots of "Summer" vegetables still to sell.

POTATOES

WARNING! Late blight has been found in southern, central, and northern Aroostook. The wet weather of the past week has created ideal conditions for the spread of late blight. The "finds" of late blight have been few, scattered, and rather small as of this writing. ALL GROWERS NEED TO BE SCOUTING ALL FIELDS, CAREFULLY! When scouting for late blight, growers need to be scouting the entire field. The traditional low areas need to be checked, as well as, the high knolls. The low areas tend to hold the moisture, as well as, the humidity and fog, creating ideal conditions for disease developments. The knolls and areas behind tree lines can "trap" windblown spores. If late blight is found in your field killing the vines before harvest is important to prevent infection of the tubers. For organic growers treatment for managing late blight this late in the season is probably not recommended since little additional growth is going to take place. If you are growing late plantings and you find some late blight then copper would be the recommended material.

Know what you are looking for. Many potato fields that I have seen are going down now do to earlier feeding of leafhoppers. There is nothing you can do about that now, and of course spraying copper on these fields for late blight is less than useless.

CRUCIFERS

Cabbage moths are very active and there is a lot of cabbage worm feeding.

Scout your fields carefully, especially if you have broccoli forming heads. Customers really hate seeing the worms swimming in the pot of cooking cabbage or broccoli. The Bt products such as Dipel work very well if you find the caterpillars when they are small.

CORN

During the past few weeks major inflights of corn earworm has occurred. This week moth captures decreased slightly around the state but populations are still very high. As long as nights remain warm egg laying activity will continue to put all fresh silking corn at risk. Remember, once the silks dry the moths choose to lay their eggs elsewhere.

The European corn borer’s second generation of moths continues to fly and also puts silking corn at risk. The fall armyworm is also a pest now. Bt sprays directly into the silk channel or a Bt/oil mixture has been shown to help. If you have some fresh corn give this a try on some of the crop and keep records of what you do. Compare to some untreated ears in the same block and let me know the results. The preliminary results of our test of an oil/Bt mixture applied with a special applicator indicates very good control.

(About the author: Eric is MOFGA’s "extension agent" and can be reached at the MOFGA office to answer your questions about farming and gardening. Link to MOFGA Contact Page, or email Eric directly.)