MOFGA Pest Report 2004
June 12

(View List Of All 2004 Pest Reports)

STILL COLD

CUTWORMS STILL VERY ACTIVE

The second most common problem I see and hear about so far this year is cutworms. There are many species of cutworms found in northern New England. They can be a problem on tomatoes, peppers, eggplants, carrots, onions, broccoli, cabbage, artichoke and the list goes on. The worst damage is in the spring. Damage varies from foliar damage along the leaf edges where the entire leaf may be eaten leaving only the midrib if left to be, to small seedlings being cut off at the base.

The cutworm is a caterpillar that lives buried in the soil during the day and comes out to feed at night. The moths fly in and lay eggs on plants. Some species arrive very early in the spring, others arrive in the summer or fall and overwinter. In both cases weeds swell the problem because they provide a great egg laying site for the moths. Growers notice the problem in the spring mostly because we have just cleared the fields of most of the food for the cutworms (by tilling or plowing) and planted only a small bit to replace it, i.e., our transplants or newly emerged seedlings. Usually these are in nice neat rows and the cutworms just march up and down the rows at night. Compounding the problem, natural bio-control agents are less active early in the season.

Being caterpillars Bt will kill the cutworm. Cutworms that are foliar feeding can be controlled by foliar applications of Bt. Apply the spray in the evening when the cutworm activity is greatest. Very good spray coverage especially on the lower leaves is important. I bet Entrust would work too.

Cutworms that are clipping off transplants and seedlings at the base are much more difficult to control because there is little surface area to cover with spray and vast damage is done before the pest eats enough to die. I have heard good reports from people who have made a bait to attract and kill the cutworms. The bait is made from bran moistened with a Bt solution (very concentrated) and made more attractive with some molasses. Some people just sprinkle this along the rows and others make small patties and place them along the row of crop.

On a small scale, Dixie cups with the bottom cut out work well as collars to keep the cutworm away. Weed control through the season and into the fall is very important.

ENTRUST

Last year an approved formulation of spinosad was introduced (Entrust). It proved to be extremely effective against Colorado potato beetle and caterpillars on farms across the state. It is reported to be quite effective against thrips and leaf miners as well. Many of you have purchased it by now and see that the label gives use instructions in "ounces per acre". For many growers this is hard to convert to use with a back pack sprayer on a row foot basis. A product bulletin from Dow gives conversions and along with a weight to teaspoon conversion I can give you some guidance on how to use it on smaller farms

I had one of our most trusted MOFGA guys weigh it and a half teaspoon of Entrust weighs one gram. If the amount of Entrust recommended on the label for a particular pest is one ounce per acre, then use 0.69 grams (a bit less than half a teaspoon) per 3 gallons of spray on 1000 square feet. You can see that although it is quite expensive it goes a long way. And, being a dry powder, I would expect the shelf life to be long.

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.

STRIPED CUCUMBER BEETLE DUE TO ARRIVE SHORTLY

Striped cucumber beetle numbers are likely to jump rapidly in the next week. They are, so to speak, 'waiting in the wings' for the return of warm, sunny weather. Direct-seeded pumpkin, winter squash, melons and cucumbers that are just emerging, as well as cucurbit transplants that are still young are highly susceptible to both feeding damage and transmission of bacterial wilt, which is vectored by the cucumber beetle. The cotyledon up to the five-leaf stage is most susceptible.

Beetles are very mobile and can build up rapidly, so fields should be scouted at least twice a week. Activity tends to be highest during warm sunny weather - so a change to warmer weather is likely to bring them out. Rotation makes a difference! Numbers will be higher and infestation earlier in non-rotated fields or fields adjacent to last year's crop.

We are seeing many growers trying perimeter trap crops in cucurbits. In a mixed field of various winter squash varieties, we are suggesting that growers plant the most attractive varieties at the edge - blue hubbard squash is known to be highly attractive and reliable as a trap crop, but other Cucubita maxima may also serve well as trap crops (e.g. buttercup squash). For more on PTC refer to the March 30 Vegetable Notes (archived at http://www.umassvegetable.org/newsletters/archive/index.html)

-Scouting: Look for signs of feeding on the underside of leaves, especially the cotyledons. Cotyledons are gouged on the underside, while older leaves show feeding holes across the leaf. Beetles are often found underneath leaves or in cracks in the soil. Mating pairs are common. Check sets of 5 plants in at least five areas of the field (25 plants total), noting damage and counting number of beetles on or near the plant. This can be done in about 15 minutes. Check field edges for hot spots. Beetles move in from field edges and numbers will be higher in the first rows near a woods or fallow area where they spent the winter. Border treatments may help reduce infestation of the whole field. Where you have planted perimeter trap crops, check the border frequently and spray as soon as beetles arrive. DO NOT WAIT for the beetle numbers to reach a threshold. You want to kill the beetles while they are feeding on the attractive plants in the border -- BEFORE they move or 'bleed' into the main crop.

-When to Spray: Controlling cucumber beetles in the coty-ledon to 5 leaf stage is the only way to preventing bacterial wilt. For wilt-susceptible crops such as cucumber, summer squash and zucchini, muskmelon, gourds, and some winter squashes and pumpkins, lower thresholds are needed. We recommend that growers do not allow numbers to exceed 1 beetle per two plants. Some states recommend a higher threshold of 1 beetle per plant even in susceptible crops. The time between first arrival of beetles and that threshold can be short, so keep an eye on fields once you see any beetles and spray within 24 hours of reaching threshold. For less wilt-susceptible crops (eg watermelon, calabaza), 1-2 beetles per plant can be tolerated without economic injury.

-Organic Controls: Cucumber beetle can be a serious problem for organic growers. Row covers are very effective in excluding beetles while promoting faster growth. Hoops are recommend for vine crops to prevent injury from wind blowing the fabric against the leaves. Make sure to remove covers at flowering to allow pollination. Using transplants instead of direct seeding gives plants a head start - not only over the weeds, but also over the beetle. It also allows later planting, possibly into late June, past the peak of cucumber beetle activity. Pyrethrin (Pyganic Crop Spray 5.0 EC) sprays provide moderate control. Use moderate to high rates. One way to enhance the effectiveness of this material while reducing the overall cost would be to combine it with perimeter trap cropping (PTC), so that sprays can be concentrated on the border only. See above for more on PTC.

Kaolin Clay (Surround WP) is another option. Here are some tips on using kaolin: - Surround WP acts as a repellent and anti-feedent so must be present before damage is done; apply before beetles arrive. If you are using transplants, apply before setting them out. This saves time and materials. With direct-seeded crops, apply as soon as seedlings emerge if beetles are active.

-Ensure good coverage of the foliage including, if possible, the undersides of leaves (not easy when cotyledons are close to the ground). Leaves will look like they were sprayed with white latex paint; despite this, there is no loss is photosynthesis and leaf growth. Reapply after a heavy rain.

When mixing, add the powder to water and allow it to settle slowly. Once the powder is fully wet, agitate gently. This reduces clumping. One approach is to mix a more concentrated slurry in a bucket and then add the slurry to the tank, as the dry powder could cake if added directly to the tank mix. Continuous or frequent agitation is needed in the sprayer

Although kaolin is safe in terms of skin exposure or ingestion, handlers should take precautions to avoid breathing the powder. Wear a respirator or mask when mixing and spraying. Rotenone used to be used by some organic growers. Available Rotenone products are not approved under the National Organic Program because no brands have sought approval by revealing the inert ingredients.

(reprinted and modified a tiny bit from an article in the UMASS Veg. Newsletter by Ruth Hazzard)

STRAWBERRIES

(modified from the Strawberry IPM Newsletter by David T. Handley U Maine Vegetable & Small Fruit Specialist)

Tarnished Plant Bug Populations Increase
Late Frost Threatens Cold Spots Around the State

Situation: The cool, cloudy weather was briefly replaced by very hot, humid weather for two days, only to be followed by two day of cool, windy weather and threats of frost in the colder areas of the state. All this variation in temperature can be hard on plants. Root growth has probably been slow this spring, due to cold soil temperatures and high moisture conditions. When temperatures suddenly jump into the 90's water demand on the plants is dramatically raised as the plants suddenly need to move a lot of water throughout their tissues to keep from drying out. The comprised root system may not be able to keep up with the sudden demand, and thus the plants undergo high levels of stress, which may result in wilting and delayed growth. Fields in Southern Maine are at petal fall to green fruit stage, with a few ripe fruit showing in early varieties, while fields in central Maine are at full bloom to petal fall. It looks as though the harvest season will only be slightly delayed this year in most fields despite the poor weather. Strawberry bud weevil or "clipper": Most fields in southern Maine are beyond the stage where clipper can cause significant economic harm (petal fall). However, in later fields clipper is still actively clipping buds on plants in the early to full bloom stage, so some management may still be necessary. In fields that still have a high number of unopened flower buds, check for injury and apply controls if damage exceeds the threshold of 1.3 or more clipped buds on average per two feet of row. We have found significant clipper injury and/or live clippers in Monmouth, Wayne and Dresden this week. Reminder to Raspberry Growers: Strawberry clipper will move onto raspberry buds when strawberry buds aren't available. Check raspberry flower clusters for clipped buds and live clippers. Insecticide sprays to control raspberry fruit worm adults, which are also active at this time, should provide some control of clipper as well. Products registered for clipper on raspberries include PyGanic, and Aza-Direct.

Tarnished plant bug activity climbed higher in some fields this week, probably a result of the sudden warm weather. Fields in Farmington and Dresden were over the threshold of 4 out of 30 flower clusters scouted infested with tarnished plant bug nymphs. This insect can remain a pest well into the fruit development stage, so growers should continue scouting for it. Populations are likely to rise when warmer weather settles in.

Two-spotted spider mites: Most fields were relatively free of spider mites this week, as controls applied previously have taken effect, as well as continued inhospitable weather. Mites were over the 25% threshold only in New Gloucester this week, but we recommend that growers continue scouting for this pest as it can increase rapidly in a field under warm temperature conditions, and poses a threat to strawberry plants throughout the growing season.

Vegetable & Berry Growers Twilight Meeting

Thursday, June 17th, 6:30 p.m.
Chipman Farm, Range Hill Road, Poland Springs, ME

Sponsored by
The University of Maine Cooperative Extension
The Maine Vegetable & Small Fruit Growers Association

Come join us for an evening packed with information for vegetable and berry growers at Chipman Farm in Poland Springs on June 17th starting at 6:30 p.m. This historic farm boasts a first-class pick-your-own strawberry operation, a regiment of high plastic tunnels for early season vegetable production, extensive use of mulches and trickle irrigation and a broad-based marketing approach including entertainment farming.

Chipman farm is located near the intersection of Routes 122 and 26 in Poland Springs. From the Maine Turnpike, take exit 63 in Gray onto Route 202 east. At the traffic light in Gray turn left onto Route 26. Follow Route 26 to the intersection of Route 122 in Poland Springs, turn left and follow the signs to Chipman Farm.

You can get quick access to pest management information through the U Maine, Extension web page on the Internet at http://pmo.umext.maine.edu If you would prefer to receive this message via e-mail, please give us a call at 933-2100 or send an e-mail message to: dhandley@umext.maine.edu.

If you are a person with a disability and need any accommodations to participate in the programs mentioned in this newsletter please call 207-933-2100 to discuss your needs.

(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.)