Eric Sideman's Pest Report
June 19, 2003

(View List Of All 2003 Pest Reports)

CROP CONDITIONS

More rain, more clouds, more wet leaves, more cool soggy soils. As of June 9, most of Massachusetts has received at least five inches of rain in the previous four weeks -- about two of them during the past week. As we go to press, another long, steady rain is falling. On the bright side, greens and lettuce have grown well and harvest is about on schedule. Harvest includes lettuce, spinach, radish, greens of all kinds, baby turnips, broccoli, asparagus, rhubarb, peas, herbs, cut flowers. Community Supported Agriculture farms (CSA's) opened their doors this past week, farmers markets and farm stands are open (although wet weekends have slowed sales). Row covers that have helped early crops, are being kept on longer than usual. The difference between covered and uncovered crops is very dramatic compared to other years. Early summer squash is flowering. Transplants continue to go out: pumpkin, winter squash, late tomatoes, melon, celery, and pepper. Growers are planting between rains as soon as they can get into fields.

However, the wet and cold is taking a toll and gets more serious as the weeks go by. Peppers, tomatoes and eggplant are suffering, and need heat. Plastic needs sun to get the soil-heating effect, and sunshine has been in short supply. Corn growth is slow, some seed has rotted. Perhaps the hardest hit are early-seeded butternut crops. Butternut that was seeded on the usual schedule, beginning around the third week of May, sat in soils that were too cold for germination and rotted. Many crops will have to be replanted. Other growers are waiting for fields to dry out enough to work or for soils to warm up enough to get good germination. As one grower put it, the well-drained soils make great house lots and farmers are left with the wet fields. Or, the well-drained fields have already been used this spring, and now growers need to get into the wet ones. In the Connecticut Valley, we are seeing good emergence in butternut crops that were seeded at the very end of May, and we can hope for some warmer soils to get the pumpkin crop going.

Growers are doing what they can to help soil drainage. I've been pleased to see several fields this week that had just been sub-soiled between raised beds. This reduces the risk of soil-borne disease outbreaks by releasing standing water. Raised beds by themselves are helpful, but it's also important to drain water between the beds wherever possible. Weeds are growing great. It's hard to get in to cultivate without getting stuck in the mud, not to mention that the weeds re-root in the moist soils. I tasted the first early local strawberries this week, and they were the sweetest imaginable. Berries are doing well. If it dries out a bit, we could have an excellent strawberry year.

-R Hazzard, with contributions from J Bartlett, R Bonanno, D. Dewitt, D. Rose, D. Kaplan, E. Droescher, J. Golonka.

ENTRUST

[NOTE: I had one of our most trusted MOFGA guys weigh it and a half teaspoon of Entrust weighs one gram. --ES]

For small plantings or spot sprays, add the required amount of Entrust to the recommended amount of water, mix thoroughly, and apply uniformly to plant foliage up to the point of runoff. It is recommended to mix only as much spray as needed for a single treatment. Do not use more than 3 gallons of spray per 1000 sq ft of area. If your scale cannot accurately weigh the amount needed, multiple by a factor that delivers an amount within your scale's accuracy and then divide the amount weighed volumetrically by this factor (e.g., if your scale will only accurately weigh amounts of 2 gms or greater and you only need 1 gm, weigh out 4 gms and then divide this volume into 4 parts).

If the amount of Entrust recommended on the label for a particular pest is one ounce per acre, then use 0.69 grams per 3 gallons of spray (.024 oz) on 1000 square feet.

MOFGA Twilight Meetings

CUCUMBER BEETLES

This is the point when plants are most susceptible to transmission of bacterial wilt, so control is important. Pumpkins, melons, summer squash, gourds, and cucumbers are all susceptible to wilt -- some varieties more than others. Beetle numbers can jump in just a day or two. Field edges near the woods get hit first, so scout those first. Floating row covers work well to keep beetles off the young transplants. Remember, remove periodically to weed and take off when flowering to allow pollination. Surround has been demonstrated to work well also. Transplants can be sprayed before setting out. In any case, best results occur if you spray with Surround before the beetles arrive and keep new tissue covered as it grows and the beetle pressure is still high.

LATE BLIGHT

Please note that State of Maine Regulations require that all Potato Cull Piles be controlled by Tuesday, June 10.

This is because that cull piles are a major, if not the major, source of spores for the initial infection with late blight, whether it be on tomatoes or potatoes. There was a great deal of late blight on tomatoes in Cumberland County last season and I never learned the source. If you have cull piles or volunteer potatoes coming up in last year's potato fields, please destroy them.

POTATO BEETLE: BE READY FOR COLORADO POTATO BEETLE EGG HATCH

Scouting. Look on the undersides of leaves for the orange-yellow egg masses. The fresher the eggs, the brighter orange the eggs will appear. If eggs have been around for a while, they appear a darker, brownish orange. One way to know when eggs first hatch is to flag the first ten egg masses that you see with bright surveyor's tape or flags, and then check them every couple of days. This will tell you when the earliest eggs are hatching. New eggs will continue to be laid for the next 2-3 weeks.

Timing and thresholds. Remember, at this time, no Bt formulations are approved for organic use, but for next year when we expect Novador to be reformulated you want to apply the Bt when 20-30% of the eggs have hatched and then again when the rest have hatched (about 10-14 days).

If you are using Entrust, you can wait till more larvae are hatched, until the oldest larvae reach the beginning of the fourth stage, when they are about 1/3 inch long. Applications made at this time with Entrust will kill all the larvae that have hatched up to this point. The threshold for small larvae is 4 per plant; for large larvae, 1.5 per plant (or per stalk in midseason), based on a count of 50 plants or stalks.

This season with cool conditions, beetle invasion of fields and egg deposition is slow and then hatch can be spread out over a long period of time. This situation is not good as then you can have various stages of larvae as well as adults in your field. Or, if it warms up suddenly, you will have a rapid flush of larval hatch and feeding damage that may seem to explode out of nowhere. [Hatched larvae go through four stages instars before they become adults. As the larvae get bigger, they do more feeding. The fourth, or largest, stage does 85% of the feeding damage.]

Colorado potato beetles rapidly develop resistance to insecticides. This happens on a field-by-field basis, which means that you have control over how resistant "your" beetles become to any given product.

Management strategies for CPB should use crop rotation as the main line of defense. If you need them, then alternate classes of insecticides in each generation of the beetle to prevent resistance. That is why I am hoping that Valent lives up to their promise and reformulates Novador so we organic growers can alternate Bt with spinosad.

Entrust (spinosad) is expected to give excellent control of all stages of CPB at a rate of 1 to 1.5 oz/acre. (NOTE: see above for conversion to back back sprayer rates). For a heavy population, two applications about 10 days apart, with the initial application when third instars occur, will control the first generation. Entrust has the advantage that it will control both adult and larval CPB, including larger larvae. European corn borer, which can cause tunneling damage in stalks, will also be controlled.

(Modified from a report by Ruth Hazzard)

(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.)