March 1, 2000
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 or

(adapted from Univ. of Illinois Extension)
Pheromone traps are particularly important for monitoring flights of corn earworm because it does not overwinter in the northeast. Its seasonal pattern of occurrence is dependent on the timing of immigration into an area rather than on degree day accumulations. The best way to know when immigration is taking place and thus the need for insecticide applications in sweet corn is to use a pheromone trap. Corn earworm traps are large, cone-shaped traps constructed of wire or nylon screening. (Paper sticky traps are not effective for monitoring this pest.) Traps and lures are available from Great Lakes IPM (517-268-5693) or Gemplers (800-382-8473). Lures contain the synthetic version of the pheromone that females use to attract males. Request a packet of 10 Hercon "Zealure tapes" for each trap you operate. Change the lures in each earworm trap every 14 days, and you'll need to check and empty the trap every day.Traps tell you when male moths are flying (and mating is ongoing and females are laying eggs); egg hatch usually occurs within 2 to 5 days (depending on temperatures) after moths are caught. In some Vermont locations and years early sweet corn may be damaged by earworms, but often the earworm season is shorter,  spanning only mid-August through mid-September. Some years, especially in northern Vermont, earworms do not arrive at all. However, it is best to have a trap in place whenever corn is about to form silk, which attracts the earworm moths. That way you will know whether and when spray (or to apply vegetable oil to the silks with a hand-applicator - ask me for information on this technique).

Pheromone traps may also be used to monitor European corn borer flights. Pheromone traps detect male flight, and different strains of the corn borer respond differently to slightly different pheromone blends. Thus you'll need 2 traps, baited with pheromones for the 2 different strains of corn borer. Traps for corn borer should be in place along field edges by the time corn tassels can be seen emerging from the whorls. Insecticide is recommended if 15% or more of the young tassels show feeding damage. Pheromone traps provide valuable information on the timing and intensity of corn borer flights, and trapping can also be used by pepper and green bean growers.These crops cannot rely on assessments of foliar feeding to indicate corn borer presence or density.

GREENHOUSE STRAWBERY PRODUCTION (from Cornell Cooperative Extension,

A Cornell extension bulletin from 1897 written by Liberty Hyde Bailey discusses the forcing of strawberries in greenhouses. He states that "the attempt was so successful that the methods which were employed in raising the crop are here detailed." Strawberries were rooted in pots outdoors. The potted plants were kept in a cold frame, then moved into a heated greenhouse in intervals, beginning in late December. Flowers were pollinated by hand, and the first crop was harvested from May 6th through May 16th. Each plant produced an average of 6 large berries, or one quart per 3 sq ft of bench space. Interestingly, the price they obtained in 1897 ($2.00/quart) was approximately the same as the seasonal price today. The varieties available today are more productive than those of 100 years ago. We identified one of the most productive and flavorful varieties available today (Jewel, a short-day type) and focused our research on getting it to fruit during the off-season. We reasoned that we could not compete with Florida and California on the basis of price, but perhaps we could compete on the basis of quality.

We placed dormant crowns into 6 inch pots filled with equal parts peat, perlite and vermiculite in May and June, and allow them to grow outdoors until early October. Runners and flowers are removed at regular intervals. Plants then are either moved into the greenhouse, or stored in a cold room at about 28-30F. Plants will still fruit if leaves are removed to make handling easier. Cold-stored plants are moved into the greenhouse at staggered intervals, about 12-13 weeks before fruit is desired. When plants are placed at a pot-to-pot spacing on a bench and provided with supplemental high intensity lighting, we obtain marketable yields of 12 ounces/sq ft during a 3 week fruiting period.

The use of dayneutral varieties is an alternative to the system just described because this type is insensitive to day length, and will flower soon after transplanting. They do not need a preiod of short days and cool temperatures to initiate flowers as Jewel does. Therefore, a special nursery for spring tramsplants is not required. Dormant dayneutral runner plants can be obtained from commercial nurseries in late autumn, planted directly into the greenhouse, and they will continuously flower and fruit even under long photoperiods. The fruiting season for individual plants can be several months in length as opposed to several weeks. We deflowered day neutral straberries for 2 weeks to allow for good establishment. Plant swere derunnered as well. We evaluated 5 varieties (3 from the West Coast and 2 from the East coast) and found that Tristar (developed in Maryland) not only produced the highest yields, but it was the most flavorful as well. We obtained 7 to 10 oz/sq ft  per month once fruiting began, and we averaged 8 g per berry (a typical supermarket berry from the West Coast might average 25 g). The major disadvantage of the dayneutrals was that pests were difficult to manage after the same plants had been in the greenhouse for a few months. We have had more success with Jewel than with Tristar, despite the additional number of Jewel plants that have to be moved and manipulated.

Because the weather is cloudy for much of the winter in the Northeast, we used supplemental lighting at night. Since strawberies thrive at lower temperatures than most plants, heating the greenhouse is likely to be required only at night, and the heat from the lamps often is adequate to provide sufficiently high temperatures. We used a 75/55F day-night temperature cycle. We examined various nutrient solutions and found that 50-100 ppm N is adequate for strawberries. We used a stock solution of soluble 5-11-26, plus ammonium nitrate and calcium nitrate. The calcium and ammonim nitrate were made into a 10 gal stock solution using 615 g and 130 g, respectively. the 5-11-26 is made into a separate stock solution using 1230 g. The proportioner (1/50) adds equal amounts of both to maintain a constant conductivity equal to 100 ppm (later dropping to 50 ppm once flowering begins). A 100 ppm solution consists of 2.46 g/gal 5-11-26, 0.26 g/gal ammonium nitrate, and 1.23 g/gal calcium nitrate - providing 88 ppm N as nitrate-N and 12 ppm as ammonium-N. Micronutrients were added to the soil mix. We used leaf analyses to monitor nutrient levels, and phosphoric acid to maintain the solution pH at 6.5. Additional boron was required when leaf levels dropped below 30 ppm, and iron chelate was added to the solution when leaf levels dropped below 50 ppm. Care was taken when mixing the stock solution. The phosphoric acid and iron chelate were added to the dilute solution - not to the stock solution - to avoid precipitation.

Strawberry flowers require some type of assistance to move pollen from the anthers to stigma. Bumble bees provide good pollination for strawberry plants. They perform much better than honey bees or hand pollination, and now we use them exclusively. Bumble bees are not aggressive, and we have never been stung by them - in contrast to honey bees! Bumble bee hives are short-lived, about 6-8 weeks, so they have to be replaced regularly. Bumble bees can be obtained from numerous vendors who import them from Holland or Canada.

One advantage of greenhouse production is the absence of weeds. However, the controlled climate is ideal for other anthropod and fungal pests, if they are introduced. The following pests might be encountered growing strawberries in greenhouses: shore flies, fungus gnats, two-spotted spider mites, aphids, thrips, powdery mildew, and gray mold. If one uses bees in the greenhouse, then pesticides are not recommended. We use biological control whenever possible and avoid the use of pesticides. We release Geolaelaps, Orius or Amblyseius cucumeris at the first sign of thrips, lacewing larvae and Ahphidoletes midge for aphids, and Phytoseiulus persimilis for mites. We found it is essential to have biological control agents in place before a pest outbreak begins. Scouting for pests is important, because populations can increase rapidly under the favorable, greenhouse conditions. Root diseases (e.g. red stele) can become serious if infected plants are used with a recirculating irrigation system - although in 6 years we have never had a problem. Ensure that plant material is disease-free prior to planting. We allowed the plants to grow through plastic mulch in order to keep fruit from lying on the soil mix. This barrier prevented insect larvae in the soil mix from burrowing into the ripening fruit, and reduced the incidence of gray mold on the fruit.

Producing off-season strawberries is expensive, and the break-even price for us was $3.00/pint. However, a small, but significant number of consumers are willing to pay top dollar for a fresh berry picked at the peak of ripeness and delivered to the store within a few hours. Size may not be a major factor for marketing these berries since they have such an intense flavor. They should be promoted as a special type for strawberry connoisseurs.

"Dave and I had plenty to talk about during and after our participation in the Farmer-to-Farmer NOFA conference in Tunbridge. The folks we met were so inclusive and friendly and we appreciate being asked to participate that weekend. Since Dave and I have been farming for what seems like a lifetime (since 1982) and are always looking for ways to improve systems but basically have production and marketing under our belts, our focus appears to be shifting to
quality of life issues. Attending conferences alert us to the many lifestyle problems that farmers have even though these go unmentioned in favor of farm production issues. For half the income of a conventional job, a farmer works twice as many hours. Now you can do the math and see that on many fronts there is stress caused by lack of time and money.  It is interesting that many farmers choose that profession for lifestyle reasons, but in reality, do not attain that expected lifestyle. Without intending to be cynical, it appears that small farmers are subsidizing food for the public, since a viable income is not earned in producing that product. In an article in a magazine this month, a older, local farmer was featured as a tenacious and successful farmer in a rapidly growing and developing coastal community. We know this farmer, and she has lived near poverty all of her farming life and struggled to pay for medical bills, her everclimbing taxes,etc. To whose benefit is it to misrepresent the farmer's financial reality?  Certainly not the consumers'.  And most importantly, not other farmers'!  The myth goes on and more young people think they will be able to chuck their jobs and make it on their farms. That, I believe, is a great misservice to these young people if they ever hope to provide for a family. I am not sure the time is right for small farms to expect to make it financially, although our culture needs to retain the knowledge and pass it on." (Chris Colson, New Leaf Farm, Durham ME)

The Burlington Public Market is in the planning stages and is expected to open in the summer of 2001.  Located at the old police station site along with an expanded Onion River Coop, this year-round market will be committed to: being accessible to the broadest possible public; being affordable to consumers and vendors; increasing local production of food and crafts; and offering diversity in the size, type, and mix of products offered. The Public Market's Steering Committee has hired Yellow Wood Associates of St. Albans, to work with those producers who want to be represented at the Public Market. The Public Market is intended to benefit Vermont producers. However, to provide adequate supply for a year-round indoor market, producers will need to work together. Where possible, producers should work through existing institutions like the Vermont Vegetable and Berry Growers Association, however those who wish to organize themselves regionally or across commodity groups are also welcome to participate. Please call Adele at 524-6141 if you are interested in being part of the Market.