May 15, 1999
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967


I haven't noticed much in the way of greenhouse insects so far. I'd like to think that this is because I cooked it while it was empty during August and took special care to make sure it froze up good and hard in January. The first week in May I raced to get the winter rye plowed as the hot weather started making it stemy and raised the carbon?nitrogen ratio to unfavorable levels. I'll be starting to put out tender plants during the second half of May, but this year I'm keeping a wary eye on the full moon on May 30 for a late frost. We're usually free and clear by then, but we did have a killing frost June 3rd about 10 years ago. Cucumber beetles are especially bad in late May. I use hot caps for the beetles and cold on cucurbits. (Starksboro)

Spider mites found under bottom leaves of greenhouse tomatoes and a lot on some ornamentals. Released one of two treatments of P. persimilis. Bye-bye spider mites on ornamentals and in one of two greenhouses; one tomato house still has some. Second release this week. Stay tuned. We had excellent results last year with two releases only. Dry as a chip in the field. Some germination only after irrigating seeds. (Shaftsbury)

Fields are dry. Greenhouse is full, a few aphids and whiteflies are now being predated on by mail-order mercenaries. One intern has come and gone and may be returning (hellooooo). Credit card starting to melt from frequent use, CSA checks trickling in have cooled it off a little (Williston).

Blueberry plants look good - don't see very much winter injury, maybe a bit on a few of the younger plants. Things are dry but not too bad yet, waiting for rain before turning on the irrigation. Getting blueberry maggot yellow sticky traps to put out in early June. (Charlotte)

Strawberries on our sandy soil are very dry and we're starting to irrigate. Waiting to put in new plants until rainfall or bigger irrigation system is ready to go. Looks like at least 10% of the plantings suffered serious winter injury because we had so much winter rain followed by freezing and no place for water to go except low spots in the field which then iced over. This year we're planting everything on raised beds to keep plants out of the low spots. We put floating row cover on one early block of Annapolis. Whiteflies in greenhouse, Encarsia formosa bio-controls ordered and on the way. (Fairfax)

Early crops all planted on time with no problems getting into the fields. Good rain last week, but it has returned to windy and dry and we're starting to fret over newly germinating seeds (carrots, onions, and beets especially). We've just ordered a new irrigation system, set up all pumps and have sprinklers in place. It is feeling like June already. We have seen lots of flea beetles, but little else of concern. With almost no rainy days in April, the only thing we're wondering is when we'll get to spend some days transplanting tomatoes in the greenhouse. (Amherst, MA)

No pests or diseases, just dry and windy. We have direct seeded lettuce, greens, brassicas, onions, carrots, beets, spinach, etc. Everything is up. Brassicas are safely tucked away under row covers, although we have not seen any flea beetles. Hoping to put in transplants we have been holding off on, with the anticipation of predicted moisture. Onions were flame weeded last week just before emergence, not enough weeds in the carrots or beets to bother. (Hadley, MA)

With only .48 inches of rain in our area, we have been irrigating since early April. All crops growing fast with the abundant sunshine. Peas are up 4?6" and first lettuce and spinach ready to harvest from season extension houses unheated hoops) and radishes out of the field. Flea beetles are very abundant already. Strawberries are in full blossom (Earliglow and other early varieties). Orchard will be flowering soon. (Argyle,NY)

GROWING DEGREE DAYS (GDD) is a measurement of the growing season's accumulated heat. Keeping track of GDD is almost essential for precise management of pests and diseases. It is also very helpful for optimizing the timing of sequential plantings of crops like sweet corn (see The Grower, December 1997). The more years you track and record GDD, the more useful the information will be to you on your own farm. A good maximum-minimum thermometer is all the equipment you need to begin. Then, starting in early spring, the 'daily degree days' is determined each day by taking the average temperature for the day (the maximum temperature plus the minimum temperature, divided by two) minus the threshold, or base, temperature (50 degrees F for most vegetable crops and their insect pests). The daily degree days are continuously added up to calculate the accumulated GDD for the season. Here are some predictions provided by Michigan State Extension as to when pests will appear, based on GDD accumulated starting March 1 using a threshold temperature of 50 F. (Note: Predictions are estimates, based on historical records and pest biology information. Data is less accurate for soil insects since GDD uses air temperature data.) Flea beetle adults: 150-200, Imported cabbageworm adults: 150-200, first larvae: 300-400, Common asparagus beetle first eggs: 150-240, Colorado potato beetle adults: 160-240, Onion maggot first eggs: 230-280, Mexican bean beetle adults: 430-500, European corn borer: first 1st generation eggs: 450-500, first 2nd generation eggs: 1450-1500, Variegated cutworm adults: 700-1100, larvae: 900-1300.

A USEFUL WEB SITE for those with an interest in current pesticide labels and/or Manufacturer Safety Data Sheets is: It will put a complete book of over 1000 labels and MSDS data sheets at your disposal. Downloadable with Adobe Acrobat and printable. The homepage is updated daily with information regarding changes to labels and MSDSs, as well as additions of new labels. And it's free. (Alan Gotlieb, UVM)

HOMEMADE WATER PAN TRAPS can be used for monitoring cabbage root maggot fly in crucifers. Construct traps out of 9" plastic dog dishes, painted with Federal Safety Yellow. The color is important, and this is the most attractive color to the adult flies. Drill some 1/4 inch holes in the side, near the rim, so that in a rainstorm you still retain the flies because extra water drains out the holes. Once the traps are made, they last for years. Fill with water and add a drop of soap to cut the surface tension. Place on the ground in the cabbage field (I use two per field) and mark with flags. Flies apparently are attracted to areas of high humidity, so the water also serves as an attractant. Traps are best checked twice weekly (less dirt, flies are in better condition) but weekly is OK. The flies are small (about 1/3 inch long), rather delicate, tend to have an arched thorax and, after being in the water, a swollen whitish abdomen. Other insects will also be trapped (ladybeetles, cuke beetles, larger flies). I use the traps as an indicator of flight onset and intensity, and a trigger for when to search for eggs on stems of cole crop seedlings. (Ruth Hazzard, UMass Extension)

BLUEBERRY MAGGOTS can cause serious problems in Vermont. They overwinter as pupae in the soil, then adults usually emerge shortly after highbush berries start to ripen. They spend a week to 10 days laying eggs which hatch into larvae in about 5 days which burrow into the berries. Mature larvae will later drop out of berries and burrow into the ground to pupate. There is only one generation per year but pupae may remain in soil for several years. There may be 'hot spots' in a field, especially where large bushes or full-canopied varieties shade the ground most of the day, providing optimal habitat for maggot survival. Pruning bushes to reduce the shade they cast may reduce damage. Survival of maggots are closely linked to soil moisture, so irrigating fields may lead to higher pressure. Infestations can be detected before they reach damaging levels by trapping adult flies using yellow sticky boards. Use 4 traps per acre, placed 2 to 3 feet above ground in a shaded part of a bush. Various publications suggest that catches of 1 to 3 adults per trap or 5 adults per field per week are thresholds for insecticidal control. A relatively non-toxic short residual material should be used so it will not interfere with harvest (such as malathion or pyrethrin). Traps are available from Gempler's (800-382-8473). The baited Pherocon AM traps (Item T3305, $52.00/pk of 25.) contains the protein food attractant and the AM Supercharger Bait (Item T3701, $1.64/ea) adds ammonium acetate bait. The Supercharger bait increases the field life of the traps by 1?2 weeks. When used alone, the traps last approximately 7 days. (Adapted from Penn State Small and N. Carolina Extension)

ARE CURRANTS AND GOOSEBERRIES LEGAL in Vermont? This is an increasingly common question now that several nurseries are selling these crops. The answer is yes, they're legal. According to the Vermont Department of Agriculture there are no official restrictions on planting Ribes species. However, these crops can be alternative hosts of white pine blister rust, a disease that causes cankers on white pines and can eventually kill them. Black currant is more susceptible to this fungus than red currant or gooseberry. My advice is: avoid planting black currants if you are near valuable stands of white pine (the disease spores can travel nearly a mile in the wind). Elsewhere, plant less susceptible black currant cultivars such as Ben Sarek, Ben Nevis or Consort, and keep a close eye on red currant or gooseberries, scouting at least annually for signs of the disease: tiny yellow spots on the upper surface of the leaves, and orange-yellow fruiting bodies that produce and release spores on the leaf undersides.

BIODYNAMIC FARMING LECTURES will be held on June 6, 13 and 20 at Cate Farm in Plainfied. The impressive list of speakers is: Jean-Paul Cortens, Will Brinton, Barbara Sullivan and Trauger Groh. For more info or to register contact NOFA-VT at 434-4122.