Eric Sideman's Pest Report #1
May 22, 2003

(View List Of All 2003 Pest Reports)

This is the first MOFGA Pest Report for the 2003 growing season. The Pest Report is a service to MOFGA Certified organic Growers. I have been putting it together for the past 3 or so years. I do it by garnering information from Extension publications in northern New England, modifying their information to meet organic guidelines, and combining that with field reports I get from our local Extension folks, MOFGA inspectors and my own farm visits. I especially want to thank Ruth Hazzard and the other folks in Massachusetts for their excellent Vegetable Notes, Vern Grubinger in Vermont and Mark Hutton and David Handley here in Maine.

--Eric Sideman

FLEA BEETLE CONTROL STUDY

CUCUMBER BEETLE CONTROL STUDY

A 2-year study compared effectiveness of insecticides on management of striped cucumber beetles and bacterial wilt in direct seeded (DS) and transplanted (TP) pumpkin (variety Merlin). Results of the trial indicate the need for 'long distance' crop rotation in order for insecticides to be most effective. When rotation was to an adjacent field--different land, but close to last year's cucurbits-- beetle numbers were not reduced and insecticide effectiveness tended to decline.

Kaolin clay (Surround WP) provided significant reduction in feeding damage, less loss to wilt, and higher yield in 2001 - but not in 2002. This product is recommended for organic farmers in combination with other tactics such as rotation, row cover, using transplants (so plants are bigger when beetles arrive), and delaying planting until late June to avoid beetles. Surround can be applied to transplants prior to setting in the field.

CUCURBITS: PREVENTING PHYTOPHTHORA BLIGHT

Symptoms- This disease is caused by a different species of Phytophthora than late blight. Initial symptoms include a sudden, permanent wilt of infected plants without a change in color. Plants die quickly. The roots and the stem near the soil line turn light to dark brown and become soft and water soaked. Roots are completely destroyed and diseased plants are then easily pulled from the soil.

Most of winter squash and pumpkin crops in Massachusetts will be seeded in the next couple of weeks. Last year's dry conditions gave most growers a break from Phytophthora blight, but in the previous years many fields there were heavily infected with Phytophthora and growers remember all too clearly losing all or part of a crop to this disease. The only way to manage this disease is through an integrated approach - and cultural practices are the major line of defense. Prevention is very important because Phytophthora blight is very difficult to suppress once it starts to develop in a field. After it has occurred on a farm it is difficult to continue growing susceptible crops without Phytophthora blight reoccurring.

Infections occur when the following conditions are present:

1. A susceptible crop (cucurbits, peppers, tomatoes, or eggplant) growing in the field

2. Soil infected with Phytophthora spores,

3. Standing water (fully saturated soil).

Low-lying areas are sites where a Phytophthora outbreak could begin. We know that many soils around the state are infected with Phytophthora spores from outbreaks in past years. These resting spores (oospores) are most likely to germinate when there are alternating periods of dry soil followed by saturation. Standing water (or fully saturated soil) and warm temperatures are ideal conditions for spores (both oospores and sporangia) to germinate and release the swimming zoospores. These mobile spores will travel through the soil water, in surface water, in splashing water, or aerially in windblown rain to infect leaves, roots, crowns, or fruit. Once established, the fungus produces a yeast-like growth that contains many sporangia. Sporangia are lemon-shaped structures that cause new infections as they disperse into the rest of the field.

The following list of recommendations was developed by Margaret McGrath (Cornell University) and adapted for Massachusetts [they should be good for Maine too]. These reminders may help you decide where and how to plant, and help prevent problems later in the season. The key goals are to manage soil moisture to avoid saturated conditions that allow the disease to get started, and to avoid introducing the pathogen to new fields.

1. Select fields where Phytophthora blight has never occurred when possible. The fungus that affects cucurbits also causes blight in pepper, fruit rot in eggplant, and buckeye rot in tomato. An effective rotational period has not been identified yet. Two years has been shown to be insufficient, therefore select a field where susceptible crops have not been grown for at least 3 years. Both mating types of the pathogen have been found in fields in New York, and also in other states. Therefore it is possible for the pathogen to produce oospores, which are capable of long-term survival. Rotation will be more successful where only one mating type occurs. Selected fields should be isolated from fields where Phytophthora blight has occurred to avoid the potential of the fungus being moved (in run-off or on farm equipment) from the infested field into the cucurbit crop. Late blight of potato and tomato is caused by a different fungus (P. infestans); therefore, previous occurrence of late blight is not a concern in field selection.

2. Select well-drained fields.

3. Make sure water will be able to drain out of the field. If water does not normally drain out of the field, then make a trench between beds or rows at their ends, make a ditch or waterway across the end of the field for water coming out of the field in the trenches, and continually grade soil at the end to allow water to leave.

4. Physically separate plantings of susceptible crops (cucurbits, pepper, eggplant, and tomato). Plantings should be located such that there is no opportunity for water to move from one planting to another. The pathogen can also be dispersed in rain splash during storms. Therefore it is prudent to consider prevailing wind direction when deciding where to locate multiple plantings of susceptible crops on a farm.

5. Minimize hardpans and plowpans by subsoiling or chisel plowing before planting, and by not driving through wet fields.

6. Do not plant the crop in areas of the field that do not drain well. Plant a cover crop in place of the crop in these areas. It is worth sacrificing a small area that will never be harvested to avoid the risk of losing the entire crop.

7. Prepare raised dome-shaped beds for summer squash and other bush-type crops. Use a bed shaper to provide more lasting beds as opposed to a simple ridge. Use a transplanter that doesn't leave a depression around the base of the plant. Fill in any depressions.

8. Clean farm equipment, shoes, etc. of soil between fields. Movement in soil on equipment and shoes probably is an important means by which Phytophthora has been spread between fields on farms and may account for the occurrence of Phytophthora blight in fields with no previous history of susceptible crops.

9. Subsoil between rows after planting and before vining to improve drainage. Subsoil again as needed after rain. Good drainage is also important for driveways in fields, as symptoms have been observed first on plants next to the compacted soil of driveways, therefore, subsoiling along the edge of driveways is also needed. It is preferable to plan driveways before seeding leaving ample space, instead of seeding the entire field and then driving over plants.

10. Avoid over irrigating and fix leaks in the irrigation system that cause puddling in certain areas of the field. Normal irrigation practices usually do not encourage Phytophthora blight except when leaks frequently occur. Do not irrigate at night time when temperatures are above 70°F.

11. Select resistant varieties if possible. When growing small-fruited pumpkins, select varieties producing hard, gourd-like rinds (such as Lil'Ironsides). These have been shown to be substantially less susceptible than varieties with conventional rinds. In peppers, use a Phytophthora resistant variety such as Paladin.

--R. Hazzard, adapted from M.T. McGrath, Dept of Plant Pathology, Long Island Horticultural Research & Extension Center, Cornell University

TRANSPLANTING CUCURBITS

Table 1 lists the soil temperature requirements for several types of cucurbits. The most important factor influencing the germination of direct-seeded squash is soil temperature. Germination is inhibited at levels below 60°F and rapid at 77 to 86°F. Watermelon and cantaloupe seed will not germinate at temperature below 60°F. Seedless watermelon are especially sensitive to cool soil temperature. They require a soil temperature of 70°F for germination. One way some growers try to plant early in the season (before the average last date of frost) is by planting seed at two different depths. The shallow planted seedling will emerge first; if it is killed by frost, the second emerging seedling may survive.

TABLE 1

Soil temperature requirements for direct-seeded squash

   Species    Min. Temp.(°F)        Max Temp.(°F)    Optimum Temp.(°F)
   Cucumber        60                   105            60 - 95
   Muskmelon       60                   100            75 - 95
   Pumpkin         60                   100            70 - 90
   Squash          60                   100            70 - 95
   Watermelon      60                   105            70 - 95

Source: Knott's Handbook for Vegetable Growers

If you have the extra space in the greenhouse you might consider using transplants this year. The advantages of using transplants are 1) early maturity, 2) higher yields compared to direct seed and 3) grow out of susceptible stage to the striped cucumber beetle sooner. To offset the cost of growing transplants, growers need a higher return at the market or some other cost saving factor. Since transplants are often higher yielding, they can offset cost by increased volume for sale. Recent research at the University of Massachusetts Agronomy Farm showed that the use of transplants could increase yields by as much as 30% over direct-seeded plants planted at the same time (Table 2) and decrease the time from transplant to first harvest by two weeks.

Transplants can be started in 2 x 2 inch or 3 x 3 inch peat pots, three weeks before the target transplant date in the field. Three-inch containers need to be hand planted. Using standard cell packs also produces successful stands of transplanted cucurbits and can be used with machine transplanters. Cell sizes of 50 and 98 gave equal yield and fruit size in pumpkins, both were better than direct seeded pumpkins, in a study conducted at Cornell University (Reiners and Moyer, 2002). Seedlings should have no more than 4 true leaves at transplanting. Plants older than three weeks are subject to breakage and are more apt to suffer from transplant shock.

If you use peat pots and you are transplanting by hand rather than machine, it might be a good idea to tear down the side of the peat pot to give the roots a greater chance of breaking out of the pot. Make sure to bury the peat pot because the top edge sticking above the soil may act like a wick and draw out moisture. In a dry year, peat pots sometimes dry out even buried in the soil and the peat pot becomes a barrier to root growth. Make sure the transplants have adequate moisture so that they can establish root systems well out of the pots.

TABLE 2

Yield comparison of direct seeded vs. 3-week-old transplants of butternut squash, planted on the same day. *

Maintaining Healthy Transplants: Transplants need to go out of the greenhouse free of insect and disease problems. Below is a list of guidelines to help maintain disease free plants:

1. Purchase disease-free seed. Infected seed can be a source of black rot and downy mildew.

2. Use clean and disinfected growing containers.

3. Use a growing medium that is free of disease causing organisms, such as soil-free growing media; steam-treated media;

4. Use sanitary practices such as keeping the end of the hose off the ground, cleaning tools often, and removing debris and diseased plants quickly.

5. Keep soil and leaves from remaining wet for too long. Ventilate to keep the air moving and lower the relative humidity of the greenhouse.

Avoid over crowding the benches so that air can pass between the plants.

One common greenhouse disease that can occur is a Grey mold caused by Botrytis cinerea. Grey mold occurs when the greenhouse is too humid or the plants and the growing media are too wet. It usually occurs on the older leaves of plants that have been in the greenhouse for several weeks. It can also occur after periods of several cloudy days, as the leaves do not dry as quickly after watering.

Planting: Before planting in the field, transplants should be hardened-off. This is done by withholding moisture and fertilizer, and by exposing them to as low as temperature as possible, but no less than 54°F. When planting, the roots should not be disturbed. Roots regenerate slowly and go into transplant-shock easily. If it has been cool and cloudy while the transplants were growing, the leaves will sometimes become sunburned after field planting. Using spun-bonded row cover alleviates this problem. Hardening plants by exposing them to temperatures near 54°F (but not lower) will help plants withstand exposure to 50°F temperature. Plastic Mulch: See this section under weed management.

Row Cover: There are three advantages to using row covers; 1) they provide 2 - 3 degrees warmer air around the plants in the spring; 2) they protect plants against the cucumber beetles for the first 3 - 5 weeks after planting; and 3) they protect young plants from sunburn, wind, and hard rains. Row covers can be used without support to hold it above the plants. However, if the cover is held down too tightly, hard rains can damage small plants by beating the cover against the plant. Galvanized wire (#9 or #10) can be used for hoops. The wire is placed 5 feet apart over the plants and 67-inch wide row cover placed over it. The edges are held down by soil. Plastic row cover has been used as well. Heat builds up under the plastic so some method of ventilation should be used. Plastic is heavier than spun-bonded row cover. It should be held off the plants by wire. Row covers should be used with black plastic. Row covers used without plastic pose a significant weed control problem unless herbicide is used. Remember to remove the row cover when female flowers form to allow for pollination by bees. With transplants this can be as early as three weeks after planting. A direct-seeded planting may be covered for 4 - 6 weeks after planting before it is removed to allow for pollination.

Weed Management: Weeds influence cucurbit crops by competing for water light, and nutrients. Weeds also harbor insects and diseases, interfere with harvesting operations, and produce seeds which cause problems for years to come.

Weed management in cucurbits can be difficult. The long growing season and spreading growth habit of these crops limits later cultivations and allows many weed species to become established and produce seed. In general, use of transplants has the potential to improve weed management over direct seeding. Shading of the soil by the crop canopy is important in minimizing weed emergence and growth. With transplants, the crop canopy covers the soil more quickly after planting compared to direct seeding.

Cultivation: Cultivations should be both timely and shallow. Direct seeded crops usually require more cultivations because soil is exposed for a longer period of time than with transplants. With plastic mulch, care must be taken to insure that weeds just along the edge of the plastic are also controlled. At times, this requires hand weeding.

Cover Crops: In cases where cover crops (living or killed) are used to suppress weeds, there is still an advantage in using transplants over direct seeding. Cooler soil temperatures under a killed cover crop often result in slower crop germination. In addition, cover crops often are not dense for long enough into the season to adequately suppress weed growth. Slower crop germination combined with an extended period for weed germination and reduced ability to cultivate in the cover often result in poor weed control and reduced yields in a no-till, direct-seed situation unless herbicides are used. Live cover crops compete with the plant for light and moisture. Some growers leave a 2 - 3 ft bare alley between the plant and the cover crop to reduce this competition.

Plastic Mulch: Using plastic mulch requires weed management both under the mulch as well as between the mulch. With black plastic, weeds are rarely a problem under the mulch. Occasionally, a limited amount of hand weeding may be needed in the planting holes. Use of transplants will minimize this need due to quick shading of the planting holes. Unless soil fumigation is used, use of clear plastic promotes excessive weed growth regardless of whether transplanting or direct seeding is used.

Weeds between the mulch will always reduce crop yields, although yield reductions will be less when transplants are used. Again this is due to earlier soil shading by the crop. Weeds between the mulch strips can be controlled with a variety of methods, cultivation, flaming, hand weeding, cover crops, and with herbicides.

Flaming: Flaming can be used to kill small weeds that will interfere with crop growth. As with cultivation, it is likely that use of transplants will lessen the need for multiple applications with both direct seeding and transplanting.

For a complete reference on direct seeding and transplanting winter squashes, see Planting Cucurbits From Seed to Vining by Anne Carter, Richard Bonanno, and John Howell Department of Plant and Soil Sciences, University of Massachusetts Extension VEG1-02. Printed May 2002 (Note: This fact sheet contains both conventional and organic recommendations).

--Anne Carter, Extension Assistant Professor

Dept of Plant and Soil Sciences, UMass Amherst

Barley, oat and/or wheat growers

Late coming of warm and dry soils means it is likely that planting dates will be delayed this year for some folks. It is recommended that you make a small adjustment in your seeding rate. Since tiller development is photoperiod dependent they will develop on schedule but plants will be younger at that time. You can compensate for this effect on yield by increasing the plant population, i.e., increasing the seeding rates by 10% or 12 lbs/acre for each week past the normal planting date (May 8th in the county), but no more than a total of 40% or 48lbs/acre by June 8th. Do not increase any fertilizer since the recommended rates have already anticipated the high yield. (modified from a note from Matt Williams, if you have any questions call him at 1800 287 1469)

(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.)