MOFGA Pest Report 2004
JULY 29, 2004

(View List Of All 2004 Pest Reports)

LATE BLIGHT WARNING

Conditions have been ideal for the development of this disease, All potato and tomato growers should be on alert and scout their fields for symptoms. Look for leaf lesions first as water-soaked spots which enlarge rapidly into pale green to brown lesions and cover large areas of the leaf. In moist weather the undersides of the lesions may be coverd with a gray to white moldy growth. Infected foliage becomes brown, shrivels and soon dies. Petioles and stems are affected in a similar manner. Fruit on the tomato will get lesions too that are dark brown and greasy and soon the entire fruit turns brown.

The best management practice is sanitation. Late blight overwinters only on living tissue of these crops and since tomato tissue does not survive the winter in Maine the only real source of overwintering inoculant is from potato tubers. Harvest all potatoes, destroy culls, look for volunteers in the spring and destroy.

LEAFHOPPER

CHECK YOUR GARLIC BULBS!

(Reprinted from Vern Grubinger's Report)

If you have not yet pulled your garlic I suggest you check a dozen or more bulbs for signs of disease. With all the wet weather, I have been finding browning on the surface of bulbs at several farms, likely due to Fusarium basal rot. Mulched fields are probably more at risk. Even if the bulbs are not fully mature, they will not improved by leaving them in the soil if signs of disease are present. Pull them and dry them as soon as possible.

THE FACTS ABOUT DEER REPELLENTS

(reprinted from the UMASS Vegetable Newsletter)

Understanding How Repellents Work: Repellents disrupt and reduce instances of deer feeding on plants for a short period and must then be reapplied. Repellents are most effective when used in orchards, nurseries, gardens, and on ornamental plants. Their value for row crops and forages is limited because of their expense, application restrictions, and variable results. The use of repellents can help to protect vulnerable landscapes, but they are usually expensive and require regular application. Repellents are most effective when used as part of an Integrated Pest Management (IPM) program that may include other repellents, scare devices, fencing, vegetation management, and population control.

Repellents fall into three categories: taste, odor, and combination taste and odor. Taste-based repellents are applied directly to plants and repel deer because of their foul taste. They are most effective on dormant trees and shrubs. New growth that occurs after treatment is unprotected. Contact repellents may reduce the palatability of forage crops and should not be used on plant parts that are intended for human consumption, unless it is labeled for that use. Since taste-based repellents require actual eating of the plant material, large amounts of damage may occur by multiple numbers of deer sampling a plant and then moving on.

Odor-based repellents repel deer by their foul smell or odor. Generally, odor-based repellent products usually out-per-form taste-based products. Some odor-based repellents can be applied directly to plants while others can be located near plants you want to protect. Border applications of area repellents may protect large areas at a relatively low cost. Crops grown for human consumption cannot be protected by odor-based repellents when applied directly, except for a very few labeled for that purpose.

Combination odor and taste-based repellents provide the benefits of both types of repellents and allow for a range of combinations. They are becoming more available. In areas with high deer densities and browsing pressure, crops and landscapes can be damaged if only a taste- or odor-based repellent is used and many deer sample the plants. By combining odor- and taste-based active ingredients, effectiveness may be increased. Different formulations allow the user to change the repellent and keep the deer on guard by providing a change in the range of odors and tastes.

Applying a Commercial Repellent: Application methods for commercial repellents range from machine sprayers to manual backpack sprayers to handheld sprayers purchased at department stores. For large farms and commercial operations, machine sprayers are most economically efficient. The number of applications can be reduced by using compatible repellents (there are very few) in regularly scheduled pesticide programs.

Apply repellents on dry days when temperatures are above freezing and rain is not expected for a number of hours so they can dry properly. Whereas young trees should be completely treated, limiting repellent application to the ter-minal growth within reach of deer (6 feet above the deepest snow) can reduce the cost of treating older trees.

Repellent applications are divided into two general classes based on the time of the damage: 1) winter or dormant season, and 2) summer or growing season. Dormant sea-son damage is most common in nurseries, orchards, forest seedlings, residential landscapes, and Christmas tree crops.

It is most difficult to control due to the lack of other food sources. Growing season damage is most common in field and row crops. Apply repellents before the anticipated periods of deer browsing. The objective is to make the planted material unattractive to deer, so that they feed else-where. Once a feeding pattern has been established, repellents are usually less effective. It is important to note that if no alternative food source is available or if deer pressure is too high, even the best-planned repellent program may fail. This is why it is essential to analyze your situation.

As a preventative measure, the first repellent application of a summer control program should take place within 2 weeks of bud break. During the growing season, repellents should be applied as necessary to protect new growth, usu-ally every 3 to 4 weeks. For some crops, it may be possible to disrupt deer feeding simply by spraying a wide strip on the border of the planting. For dormant season protection, mid fall and early winter applications are recommended.

Considerations in Choosing a Specific Repellent:
*Effectiveness and Longevity*
Studies of the effectiveness of different repellents on nursery plant species and residential landscapes show large differences in all these factors. In general, it is unrealistic to expect more than 5 to 6 weeks of protection from any commercial repellent when you have high deer populations and browsing pressure during the dormant season. Protection may be longer when the conditions and seasonal factors are less severe.

Repellents can be effective for short-term forestry applications on seedlings that only need a few years of protection to grow out of the reach of deer. In agricultural applications, repellents may be suited to short-term crops such as strawberries or vegetables that only need protection during the growing season when other food sources are available for deer and they can be discouraged from frequenting the target area.

*Cost and Ease of Use
Repellents are not usually cost-effective in managing deer damage over a long period for either commercial growers or residential homeowners. Studies in New York have shown that the cost of a repellent spray program for reducing deer damage year round in orchards exceeds the cost of high-tensile deer fencing after only a few years. Money spent on repellent applications could be wasted if unusual weather conditions force deer to eat crops because of the loss of alternative foods.

Many residential homeowners are not as concerned as commercial growers about the cost factors and the use of repellents in residential landscapes is increasing. However, even residential homeowners will soon find that the long-term cost of repellents can be prohibitive and require repeated applications. Table 3 lists a representative list of repellents, their active ingredients, and the cost per ounce for different mixtures. Some repellents can be purchased as ready-to-use (RTU) or as a concentrate and then mixed with water for use as needed. In general, RTU products are more expensive per ounce than concentrates. Purchasing larger quantities of either RTU products or concentrates will also reduce the per unit cost.

Ready-to-use products are easier to use than those that require mixing and are most popular with residential users. Some of the products have mixing requirements that make them difficult to use and may not appeal to some users.

Residential homeowners are increasing looking to the use of electric and non-electric fencing options instead of repellents as the realities of cost, marginal effectiveness, and regular application become apparent. Fencing may pose problems due to aesthetic considerations, local covenants, access, and other concerns, but these problems can ad-dressed by educating community associations and neighbors. Many residential homeowners are finding the use of bird netting during the winter a reasonable alternative to the use of repellents. In the residential environment, there are large differences in the effectiveness and longevity of different repellents with similar costs. Users of repellents should ask their local cooperative extension office for current research on this topic.

-Adapted from: Jonathan S. Kays, Regional Extension Specialist - Natural Resources, Maryland Cooperative Extension.

Information provided by Rob Berghage and Jim Sellmer; Penn State Department of Horticulture.

DEER STOPPER BRAND DEER REPELLENT LISTED AS ORGANIC

The population of deer in Massachusetts continues to grow, and damage on vegetable and fruit crops can be serious. Temporary electric fencing can be an effective barrier if installed early. However, many growers are looking for methods that will succeed in smaller areas, or where fencing is not practical. Repellents are another option. The Organic Materials Review Institute, which researches, educates and publishes brand name lists of materials al-lowed and prohibited for use in the production, processing, and handling of organic food, has listed Deer Stopper, a topical spray that lasts 30 days regardless of weather. Call (888) 411- DEER for more info and visit http://www.omri.org for a complete list of OMRI-considered materials.

We published this article last year in our IPM newsletter but were not aware of any farmers who had used it or any trials where it was tested. We would like some feedback from growers who maybe tried it. Please send an email to akcarter@pssci.umass.edu and let us now if it worked or didn't work and how.

-Anne Carter-

DEER FENCING

Fencing, the construction of a barrier between the crop and the deer, is the most effective long-term solution to deer damage. The basics of fencing apply to both electric and non-electric fencing. It is important to understand that deer can easily jump a fence 10 feet high, but much prefer not to. Deer prefer to go under or through a fence than to jump it if at all possible. Thus, the bottom wire of an electric fence should be no more than 10 or 12 inches off the ground and non-electric fences should either have an even lower bot-tom wire (about 6 inches) or be of mesh construction.

Fence maintenance is critical in both applications. If a tree falls on the fence or a hole is cut in the fence, the fence should be repaired immediately. Once deer have gotten inside and discovered the crop, it will be harder to keep them out, even with an electric fence. No gaps should exist in the fence, access must be provided through gates that are closed at all times. Fences should have a clear perimeter, at least 5 or 6 feet on the outside of the fence, so deer have to cross an opening before encountering the fence. This also enhances visibility of the fence to the deer. Deer will blunder into a fence placed tight to a wooded edge and can actually damage or take down sections of a fence simply because they do not see it very well, especially smooth wire designs. Having a clear border will increase the effectiveness of the fence and aid in maintenance.

Electric fence supplies can be found at farm supply centers or through fencing specialty companies. Three fencing specialists in the Northeast are:

• Wellscroft Farm 167 Sunset Hill- Chesham Harris-ville, NH 03450 (603) 827-3464
• Kiwi Fence Systems 1145 E. Roy Furman Hwy. Waynesburg, PA 15370 (724) 627-5640
• Walnut Grove Farm 50 Cartland Rd. Lee, NH 03824 (603) 659-2044

-R.Hazzard

PEPPER UPDATE

*Aphids
Aphids fly into pepper fields in June and July. The most common species is green peach aphid (Aphis gossypii), which is light green, yellow green, or pink, with no distinc-tive markings. Aphids can easily be seen with the naked eye, but a 10X hand lens allows you to observe them more clearly. Wingless females use their piercing-sucking mouth-parts to feed on the underside of leaves. Females produce smaller, light-green nymphs, which feed in clusters nearby.

Most of the time, beneficial insects such as ladybeetles and lacewings keep aphid numbers under control in peppers. By avoiding unnecessary insecticide applications, these natural enemies can be conserved. Use of broad-spectrum insecticides, particularly synthetic pyrethroids which are prohibited on organic farms, but also organic pesticides such as pyrethrum and rotenone, to control other pests may cause aphid outbreaks. High numbers cause a buildup of sticky honeydew secretions on leaves and fruit.

Green peach aphids can vector viruses such as cucumber mosaic virus (CMV). Insecticides are not effective in controlling these viruses because the transmission occurs rapidly at low population numbers. Reflective mulches can be used to reduce virus transmission. The silver surface deters aphids from landing on pepper plants.

Aphid monitoring: From mid June to September, examine the underside of four leaves per plant on 25 plants chosen at random. Count aphids found. Calculate the average aphids per leaf (divide total by 100).

Aphid threshold: 10 per leaf. Insecticidal soaps work well for most aphid outbreaks.

SWEET CORN

Corn Earworm & Fall Armyworm Threaten Silking Corn Moths Now Widespread and at Damaging Levels

SITUATION
Early corn is just starting to be harvested in southern Maine. Many early-midseason plantings are now in silk with late plantings at the whorl to pre-tassel stage. Rain has been more than adequate for good growth in most fields, with side-dressing going on most late whorl to early pre-tassel stage corn. The warm fronts bringing showers and warmer temperatures have also brought an increase in corn earworm and our first fall armyworm of the season. Growers should be prepared to protect silking corn now.

European Corn Borer: Pheromone trap catches indicate a significant decline in European corn borer moths in most parts of the state, perhaps signaling an end to the first generation of this insect for the season. A second generation of moths often occurs near the end of the season to threaten late corn. Larval feeding injury does continue to be a problem in some fields. Feeding damage has exceeded the control threshold in fields in Biddeford, Cape Elizabeth, Lewiston, Oxford, Poland Spring and Wayne. Corn in the pre-tassel stage or beyond should be sprayed for European corn borer when feeding damage is found on 15% or more of plants sampled in a field.

On silking corn insecticide sprays are based on the number of corn borer moths caught in pheromone traps as well as feeding injury. Five or more moths caught per week in silking corn justify a spray, if fields are not being sprayed for earworm. Although moth counts were generally low this week, the threshold for silking corn was exceeded in Cape Elizabeth, Jefferson, Lewiston, Oxford and Wayne.

Corn Earworm: Nearly all locations are now being infested with corn earworm moths. Numbers of moths caught in our pheromone traps jumped significantly this week, placing all silking corn at risk. Spray frequency to protect silking corn is based upon the number of moths caught in the pheromone traps; more moths means more frequent sprays. This week a four day spray interval was recommended on silking corn for Biddeford, Cape Elizabeth, Dayton, Lewiston, No. Berwick, Oxford, and Wells. A five day spray interval was recommended for Jefferson, Warren and Wayne. A six day spray interval was recommended for New Gloucester, Nobleboro and Poland Spring. Some fields in northern areas do not yet have silking corn and therefore do not need to protect against corn earworm at this time.

[Note: When using the Zealater silking corn should be treated when the silk just begins to wilt and needs to be treated only once. You only need to treat for corn earworm if the corn is silking AND moths are being caught in your area.]

Fall Armyworm: Fall Armyworm moths were caught in pheromone traps in most southern and coastal locations this week, signaling the anticipated arrival of this pest in Maine. Armyworm moths prefer to lay their eggs on young corn plants. When the eggs hatch the young larvae chew channels in the leaves between the veins. As they get older and larger the feeding holes become larger and ragged, often surrounded by masses of wet sawdust-like waste. When found, this injury is combined with any European corn borer injury to determine if protection is needed. Control thresholds are 30% infestation in whorl stage corn or 15% for corn at pre-tassel and beyond. No fresh armyworm feeding injury was found this week, but we can expect to see it soon. On silking corn, moths may lay eggs directly on flag leaves or husks, and the larvae may move into the ears without leaving visible feeding signs to be picked up when scouting. Therefore, if not spraying for earworm, and three or more moths were caught in a week, a spray would be recommended on all silking corn.

Sweet Corn IPM Weekly Scouting Summary

Location CEW Moths ECB Moths FAW Moths %ECB damage Recommendation

Biddeford 12 1 3 30% 4 day spray interval recommended on silking corn
Cape Elizabeth I 27 5 6 35% 4 day spray interval recommended on silking corn
Cape Elizabeth II 75 4 11 15% 4 day spray interval recommended on silking corn
Dayton I 11 1 4 day spray interval recommended on silking corn
Dayton II 19 0 1 5% 4 day spray interval recommended on silking corn
Dresden 0 0 8% No spray recommended (only one update this week)
East Corinth 17 13 0 2% No spray recommended (no silking corn)
Farmington 0 1 1% No spray recommended (only one update this week)
Garland 2 15 0 4% No spray recommended (no silking corn)
Jefferson 7 12 0 1% 5 day spray interval recommended on silking corn
Levant 14 0 0 2% No spray recommended (no silking corn)
Lewiston I 2 2 4 18% 6 day spray interval recommended on silking corn
Lewiston II 16 33 2 28% 4 day spray interval recommended on silking corn
Litchfield 0 3 4% No spray recommended (only one update this week)
Monmouth New Gloucester 2 2 6 0% 6 day spray interval recommended on silking corn
Nobleboro 2 1 0 8% 6 day spray interval recommended on silking corn
North Berwick 10 3 3 11% 4 day spray interval recommended on silking corn
Oxford 11 27 1 24% 4 day spray interval recommended on silking corn
Poland Spring 2 0 3 21% 6 day spray interval recommended on silking corn
Warren 6 1 0 3% 5 day spray interval recommended on silking corn
Wayne 8 10 0 27% 4 day spray interval recommended on silking corn
Wells 10 1 2 11% 4 day spray interval recommended on silking corn 

CEW: Corn Earworm (only fresh silking corn should be sprayed for this insect)
ECB: European Corn Borer
FAW: Fall Armyworm

Corn Earworm Spray Thresholds for Pheromone traps
Moths caught per week Moths caught per night Spray Interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every six days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every three days
Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80*F.

(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.)