Eric Sideman's Pest Report
July 4, 2002

Crop Condition

NOTE: This Pest Report is still going to the old list. Switching to the new list of certified growers is planed for the next report which will not be until mid July.

PEAS- FUSARIUM WILT

There are at least 6 races of Fusarium of peas and it would take a lab culture to determine which one is out there but there is one. Symptoms of the races differ but they are similar. The key is yellowing of the leaves starting with the lower leaves and working up the plant. In hot weather like we have had this week the disease progresses very rapidly and the whole plant will yellow and die in less then a week. The stem turns brittle near the soil line but the root system often is healthy looking.

The disease is caused by Fusarium oxysporum, which can persist in the soil for over 10 years. It is disseminated through the movement of contaminated soil, plant fragments, water, wind, tools, etc. It is commonly transmitted by contaminated and infected seed.

In my field I have three varieties of peas and only my snow pea has it. I believe it came with the seed.

PLEASE GET BACK TO ME IF YOU HAVE THIS PROBLEM AND TELL ME WHAT VARIETY OF PEA HAS IT IN YOUR FIELD.

The only economical control of Fusarium wilt of peas is varietal resistance. Of course, good cultural practices are necessary too. Rotation and sanitation is a must if you have this in your soil. Early planting so peas mature before the soil warms and the disease spreads rapidly helps.

WATCH FOR ONION THRIPS
Hot weather brings not only tiring and sweaty fieldwork, but also onion thrips, which can cause considerable damage to onions and other alliums and to cabbage. Their populations can increase very rapidly during hot weather and may go unnoticed until serious losses occur. Thrips are night feeders and hide during the day. Scout fields: by looking in the dark areas between leaves. It is important to control these insects early while populations are low.

Identification: When they are immature they are from 0.5 to 1.2 mm, with an elongated, elliptical and slender body that is white to pale yellow. Their eyes have darker coloration and are easy to see. Immature thrips have short antennas. The difference between immatures and adults is that immatures do not have wings, so they cannot fly. The majority of immature thrips are found between the young leaf blades at the top of the plant. To observe them you need to separate the leaves from the neck. The pupae are pale yellow to brown and appear as an intermediate form between the immature and the adult. They have short antennae and the wing buds are visible but short and not functional. At this stage thrips do not feed. When they are adults they are pale yellow to dark brown and can be up to 2 mm. Adults have fully developed wings that are very different from other insects. They have a single longitudinal vein in which there are several hairs connected perpendicular to the vein. The wing appears as fringe with hairs. When at rest, the wings are folded along the back of the insect. Adults are more mobile than immatures and pupae because they can fly. They are attracted to yellow and white colors. They often will fly to one's clothes or land on exposed skin.

Seedlings: Direct seeding of onions prolongs the growing season in the field and the susceptibility to thrips infestation.

If the crop is going to be transplanted, the seedbeds should be distant from the old plantings and new plots to be planted. It is very important that onion seedlings are clean of thrips before transplanting to the field. Remove unharvested plant parts volunteer onion plants are an important source of infestation for thrips. Thrips prefer to feed on the young plant tissue on the newest emerged leaves. When the leaf grows, the previous damage produced by the thrips enlarges, leaving empty spaces in the surface of the leaf. The appearance of the damage is silvery patches or streaks on the leaves that shine in the sun. When damage is severe, these small patches can occupy most of the surface of the leaf and the plant cannot adequately photosynthesize. The plant loses more water than normal through the damaged tissues and plant pathogens penetrate the injured plant easily. (from John Howell, Stephanie DeGray & Cornell University)

SWEET CORN IPM NEWSLETTER (DAVID HANDLEY, U. MAINE)

No. 3, July 3, 2002
Warm Weather Pushes Corn Growth!
European Corn Borer Remains No. 1 Threat

SITUATION
The warm weather and rain showers in most of the state this week have pushed corn growth significantly. Despite the relatively slow growth early on, some fields started under rowcovers are now silking. Most fields are now at the whorl or pre-tassel stage.

European Corn Borer: Pheromone trap catches have dropped this week, but the flight of European corn borer moths continues. These moths will be laying eggs on any corn plants available, including those in silk. Silking fields should be protected when 5 or more moths are caught in a week. Sprays for European corn borer were recommended on silking corn in Cape Elizabeth, Dayton, Litchfield, North Berwick, New Gloucester, and Poland Spring.

Corn in the whorl stage should be scouted for damage which will be shot holes in the leaves as they open. European corn borer feeding damage is more widespread this week, exceeding the threshold in tasseling corn in Wells. Fields with European corn borer should only be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field. Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15%.

Bt kurstaki is the recommended spray for whorl corn above threshold and silking corn in areas where trap counts are high.

Corn Earworm: We continue to capture a few early arriving corn earworm moths in pheromone traps in southern and central Maine. Single moths were caught in Cape Elizabeth, Lewiston, Litchfield, and New Gloucester. Fields not yet in silk do not need to be protected from corn earworm. When more than one corn earworm moth is first caught at a site, all silking corn in the fields should be protected with a spray. Typically, fields that are not silking do not need to be protected from corn earworm. However, if larvae are found feeding on younger corn, the damage is accounted for along with any borer or armyworm damage to determine if a spray is warranted.

Bt kurstaki and Bt/oil mixtures have been shown to be effective for corn earworm control if injected directly into the silk channel. We tested a system for delivering the spray effectively that is called the ZEA-LATER. It was developed by Ruth Hazzard at U Mass and tested throughout New England. We (MOFGA) had good results here in Maine when we tested it. Johnny's is carrying this new tool now.

Sprays should be made when trap counts are high and only on corn with silk that is just beginning to wilt. Corn before the silk stage is not at risk of egg laying, corn with fresh silk may suffer pollination problems when using the oil mix, and it is too late for corn with brown silk.

Fall Armyworm: No fall armyworm moths have been captured yet and no feeding damage has been observed to date. If you have any questions about insect trapping or field scouting corn, we'd be happy to help. Call Highmoor Farm at 933-2100 or the Pest Management Office at 1-800-287-0279.

Sweet Corn IPM Weekly Scouting Summary

Location, CEW, Moths ECB, Moths FAW, Moths %ECB damage, Recommendation
Auburn,  0,  82,  ,  0%,  No spray recommended (no silking corn)
Cape Elizabeth I,  0,  88,  ,  4%,  1 spray recommended on silking corn for ECB
Cape Elizabeth II,  1,  13,  ,  ,  No spray recommended (no silking corn)
Corinth,  0,  5,  0,  0%,  No spray recommended
Dayton I,  0,  14,  ,  ,  No spray recommended (no silking corn)
Dayton II,  0,  14,  ,  2%,  1 spray recommended on silking corn for ECB
Dresden,  0,  58,  0,  ,  No spray recommended (no silking corn)
Farmington I,  0,  4,  ,  0%,  No spray recommended
Farmington II,  0,  42,  ,  ,  No spray recommended (no silking corn)
Garland,  0,  1,  0,  9%,  No spray recommended
Jefferson
Levant,  0,  1,  0,  ,  No spray recommended
Lewiston,  1,  67,  ,  0%,  No spray recommended (no silking corn)
Litchfield,  1,  6,  ,  0%,  1 spray recommended on silking corn for ECB
Monmouth,  0,  13,  0,  ,  No spray recommended (no silking corn)
No. Berwick,  0,  10,  ,  11%,  1 spray recommended on silking corn for ECB
New Gloucester,  1,  36,  0,  2%,  1 spray recommended on silking corn for ECB
Nobleboro
Old Town,  0,  2,  0,  ,  No spray recommended
Oxford I,  0,  13,  ,  ,  No spray recommended (no silking corn)
Oxford II,  0,  72,  ,  ,  No spray recommended (no silking corn)
Poland Spring,  0,  6,  3%,  ,  1 spray recommended on silking corn for ECB
Warren
Wells,  0,  16,  24%,  ,  A spray recommended for ECB on tassel stage corn

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

Pest Management Web Page: www.umext.maine.edu/topics/pest.htm.

(Adapted from report by David T. Handley, Vegetable & Small Fruit Specialist

Highmoor Farm
P.O. Box 179
Monmouth, ME 04259
(207) 933-2100

Pest Management Office
491 College Ave
Orono, ME 04473
1-800-287-0279

POTATO BEETLE

The first Colorado potato beetle eggs have hatched in southern and central Maine and it is now time to spray with Bt San Diego if you have seen egg hatch in your fields. Remember, the Bt is not effective against adults or large larvae and does not remain effective for more than a day, so there is no point in spraying unless you have small larvae present.

WORKSHOP NOTICE:

Identification and Organic Management of Vegetable Insects and Diseases

1:00-4:00 PM on Sunday, July 21

Janet Britt's Buttermilk Falls Organic Farm in Schaghticoke, NY will host a NOFA-NY workshop on Identification and Organic Management of Vegetable Insects and Diseases from 1:00-4:00 PM on Sunday, July 21. We will tour the farm's diverse vegetable crop fields, identify insect and disease problems we find, and discuss organic control options. Typical pests of various crops will be covered, even if we don't find them on site. References for pest identification will be given so that farmers can be prepared to check for them in their own fields. Brian Caldwell, NOFA-NY Farm Education Coordinator, will lead the discussions.

This workshop is free and open to all. It will focus on commercial organic farming methods. We encourage, but do not require, pre-registration. Call 518-734-5495 to pre-register.

Directions: Buttermilk Falls Organic Farm is located at 333 Buttermilk Falls Road in Schaghticoke, NY. Buttermilk Falls Rd is south off Rt 67 between Schaghticoke and Mechanicville. We are about 25 miles northeast of Albany and about 10 miles north of Troy.

>From the east take Interstate 90 to 787 north at Albany. Take exit for Troy and Bennington (Rt 7 east) At the first light after the bridge, turn left on Rt. 40 north, Oakwood Ave. Follow Rt 40 north about 10 miles. At the juncture of Rt 40 with Rt 67 (just before you get to the village of Schaghticoke) turn left on Rt 67 west, go about 2.5 miles, make a right on Buttermilk Falls Rd. Go 1/2 mile on the right.

Brian Caldwell
Farm Education Coordinator
Northeast Organic Farming Association of New York
180 Walding Lane
Spencer, NY 14883
607-564-1060
education@nofany.org

(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.)