MOFGA Pest Report 2005
May 3

(View List Of All 2005 Pest Reports)

Introduction

Here is the first Pest Report of the 2005 growing season. If you want to continue to receive these on a somewhat weekly basis through the growing season, and you are not a MOFGA certified grower who will automatically get them, then you should send MOFGA an email note to that effect.

So far this season has been very wet. I would not be surprised if early planted seeds are rotting in the ground because with it cool and wet they sit and sit and this gives a chance for the soil critters and fungi to feed on them. It may be a very interesting year for Pest Report readers, but for now here is a bit on a few regulars.

Cutworms

Some cultural practices may have good results. Since the moths tend to lay their eggs at the base of plants, especially grassy areas, keeping fields bare (free of crops, cover crops or weeds) in the late summer/fall will reduce egg laying areas. Or tilling in the mid-late fall, after egg laying, will expose the cutworms. Of course, this goes against all good soil husbandry and so I would never recommend not using cover crops to avoid cut worms.

Starving the cutworms in the spring is a practice that may work and has less detrimental effects on the soil. As soon as weeds or overwintered cover crops start greening up in the spring, till the field and keep it clean with frequent tillage for a few weeks before planting crops. The overwintering cutworms will have nothing to eat and die, and the frequent tillage will expose them to predators.

Bt will kill these critters, but sprays are rarely effective because the pests do so much damage before they eat enough to be killed. Some of our growers have had good results from making a Bt laden bait with a very concentrated Bt solution, bran and molasses and then either making patties and placing them along the rows, or sprinkling the bait along the rows. On a small scale, the best method is to create a barrier by cutting the bottom out of a paper cup and placing it over each transplant and burying the bottom an inch or so into the soil. This will not work for crops like onions or carrots.

Damping Off

This has been a bad year for damping off because of the extended wet and cloudy weather that has effected even crops in the green houses. Nothing seems to dry, and the continued dampness on the soil surface is ideal for the fungi that cause damping off.

Damping-off is a common disease that kills seedlings in the greenhouse. Damping-off can kill both germinating seeds and young seedlings. Several fungi can cause this disease, including Rhizoctonia solani, Pythium spp., Phytophthora spp., Sclerotinia spp., and Botrytis spp. Most of these fungi can also cause cuttings to rot. These fungi are found in practically all soils and pose a large threat to plant propagation. Practically all species of plants can be affected.

Symptoms. Damping-off often is often seen in round patches in seeding flats. Preemergence damping-off is a term used to describe the rot of seeds, or the death of the seedlings, before they emerge from the soil. Post-emergence damping-off affects seedlings that have already emerged from the soil. These seedlings may develop a dark stem rot near the soil surface which will cause them to fall over and die as the rotted area shrivels.

They may also rot from the tips of the roots. If your seedlings look weak, pull up a plant and inspect the roots for brown, dying tips. If the seedlings live a while, this rot will progress up the seedling until the stem is rotted. Seedlings that survive until they are a bit older before they are infected may develop "wire-stem", a condition in which the base of the stem is partially invaded by the fungus. There is often a discolored and slightly shriveled or constricted area at or just below the soil line. Although the plant lives for a while, it is stunted and pale, and often will eventually die. Brown or white fungal growth may be seen on the surface of the potting media or on the seedlings themselves.

Prevention. The best way to control this disease is to prevent it. There are many prevention techniques, and a combination of them is most effective.

• One way to help prevent this disease is to keep the fungi that cause it out of the flats of seeds. Plant seeds and root cuttings only in sterilized seedling mix or other planting media, using only sterilized containers. When making your own soil mix, you may want to "sterilize" it. This can even be done on a small scale in your home oven. Bake it at 350°F for 45 minutes or until the soil is about 180o F for 30 minutes. This should kill the pathogens and yet leave enough of the soil microbes alive.
• Use only clean non-recycled water on the seeds.
• Place seed trays on clean, sterilized benches.
• Do not allow soiled hands and tools to come into contact with the sterile media. Reintroduction of the fungi can cause fast disease progression because other fungi which normally compete with these fungi are absent from sterile mixes.
• Remove any trays with damping-off immediately.
• To help prevent this disease, it is also important is to encourage the seeds to germinate and grow as fast as possible. Plants are only susceptible to damping-off as seedlings.
• Use adequate light and heat to germinate and grow seedlings quickly.
• Bottom heat may speed germination.
• Avoid planting seeds too deeply.
• Also important, to help prevent this disease from causing huge losses (although some loss may occur) is to keep conditions in the seeding trays less favorable to the fungi. These fungi like wet conditions.
• Use well-drained planting media.
• Sow seeds thinly to allow air to circulate between seedlings.
• Avoid excessive watering.

[Adapted from an Extension Bulletin by Pamela S. Mercure, IPM Program Assistant, University of Connecticut, 1998]

Two biological control materials are now available that claim to have good results with damping off. Both are OMRI approved. If you use them, let me know what you think. Please try a flat untreated as a control.

SoilGard [note: This is not registered in Maine at this time]
Biocontrol Agent: Gliocladium virens GL-21
Target Crop/Pathogen: damping-off and root rot pathogens especially Rhizoctonia solani and Pythium spp.
Crop: ornamental and food crop plants grown in greenhouses, nurseries, homes, and interiorscapes Formulation: granules
Application: granules are incorporated in soil or soilless growing media prior to seeding
Manufacturer/Distributor: Certis, Inc., 9145 Guilford Road, Suite 175, Columbia, MD 21046 USA; Phone 1-301-604-7340; FAX 1 301-604-7015, www.certisusa.com

RootShield ,
Biocontrol Agent: Trichoderma harzianum Rifai strain KRL-AG2 (T-22)
Target Pathogen/Disease: Pythium spp., Rhizoctonia solani, Fusarium spp.
Crop: trees, shrubs, transplants, all ornamentals, cabbage, tomato, cucumber
Formulation: granules or wettable powder
Application: granules mixed with soil or potting medium; powder mixed with water and added as a soil drench
Manufacturer/Distributor: Bioworks, Inc., 122 North Genesee St., Geneva, NY 14456 USA; Phone 1-315-781-1703; FAX 1-315-781 1793, www.bioworksbiocontrol.com

THE NEW ENGLAND VEGETABLE AND FRUIT CONFERENCE SCHEDULED FOR DECEMBER 13, 14, 15 2005

(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.)