April 15, 1998
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 verng@sover.net

Integrated Pest Management (IPM) is an approach to managing pests that uses pesticides only when crops are threatened with significant damage. To minimize the need for pesticides, crop rotation and cover cropping are practiced, disease-resistant varieties planted, and physical pest controls employed such as floating row covers, mulches, and cultivation. However, pests inevitably still show up, and monitoring for their arrival is key to optimizing pesticide effectiveness so that sprays are applied when they will do the most good. That's why it's important to get out and scout your crops for insects, diseases and weeds on a weekly basis. Getting information about what's happening on other farms can serve as a reminder to scout a particular crop, and alert you about what to look for.

This year in Vermont we will pilot an electronic IPM network of growers that volunteer to scout a certain crop on their farm and report the results to me via e-mail. Besides pest problems, we'll be looking for reports on crop development, winter injury, production innovations and other tips useful to fellow growers. A compilation of these reports will appear in this column. If there's a crop you pay close attention to and whose insects and diseases you are familiar with, you have e-mail, and you can commit to sending in a report every 2 weeks - let me know!

Last year, I conducted an experiment to compare the effect of different mulches on the yield of field-grown tomatoes. The variety 'Jet Star' was grown in fields next to my office in Brattleboro, on a gravelly loam soil with drip irrigation. The plastic mulches were 4 feet wide, so beds were 3 feet wide on 6 foot centers, with plants spaced 3 feet apart in the row (2,420 plants/acre). There were 8 plants in each mulch strip, with 4 replications per treatments. Based on a soil test, 100 lb/acre N plus 90 lb/acre potash fertilizer was rototilled in prior to laying the mulches. Transplants were set on June 13, first harvest was on August 28, final harvest on September 24. Plants were not staked or sprayed during the season, weed pressure was high (I had to weed-whack between the rows), and the spring went dry due to lack of rain so for a few weeks there was no irrigation. That's why I leave the farming to you guys! However, there were significant differences among the treatments which illustrate the benefits of using mulches.

Mulch Treatment                         First Harvest Total Harvest
                                                    (lb of marketable fruit per plant)
Bare Ground                                 1.5                  6.9
Black Plastic                                 1.7                  8.4
IRT Plastic                                   1.7                  8.9
Planters Paper                              1.4                  7.2
Red Plastic                                   2.1                10.2
Straw 6" thick                               1.4                  8.1
White Plastic                                 1.8               10.2

By the way, to determine how much plastic mulch is needed per acre, divide row spacing (center to center) into 43,560 (sq. ft/acre). For example, if row spacing is 6 foot on center, divide 43,560 by 6 to get 7,260 linear feet of mulch per acre. Thanks to Fred and Laura Bacon (UVM Master Gardeners) for helping with this project!

The new 162-page Strawberry Production Guide from NRAES is out, and it's just as good as the Highbush Blueberry and Bramble Guides that preceded it. Maybe better - it even comes with diskettes for PC or Mac that contain profit spreadsheet templates. Copies are on their way to my office - we'll be selling them for $55. Make your check to UVM Extension and please include a note saying what it's for.

A foliar application of Solubor (1.5 gallons in 100 gallons water) can provide boron, which is needed for early-season cell expansion and growth in perennial fruits. However, in the spring when roots are cold and transpiration is low, boron may not be moving out to the growing tips because it is not very mobile in the plant. Boron plays an important role in flower fertilization and fruit set by accelerating pollen germination and growth of pollen tubes, and can be especially beneficial when fruit set and yields suffer due to poor weather during bloom. It is best to apply boron at or before flowering in spring. Fall-applied boron is another option, as it moves rapidly out of treated leaves and into flower buds where it will be available next spring. Do not over-apply boron, as high rates can cause crop injury.

That's the cover story of HortTechnology April-June 1988. The author, Thomas Li, provides the following cultural practice suggestions: stratify seeds before planting by mixing 1:1 with clean sand and storing at 34 to 39 degrees F in a plastic bag at 10% moisture for 4 to 6 weeks. Sow seeds no more than 1/4 inch deep in a 1:1 mix of peat and perlite, hold flats at 64 to 68 degrees F. In the field, maintain soil pH at 6 to 7, avoid high N fertilization levels which will promote high shoot yield but low root yield. Set transplants at high densities for best root yield, spacing 12 inches apart in the row and 12 inches between rows, although this may be too dense for more vigorous species, or if plantings are kept more than 4 years. Use black plastic or bark mulch to reduce need for hand weeding. Call my office for a copy of the article.

Trichoderma harzianum is a naturally-occurring beneficial soil fungus that is active against several root-rot organisms, and has been shown to enhance plant vigor that was lost due to certain stresses, even in the absence of disease. Dr. Tom Bjorkman of Cornell gave an enlightening presentation at the VV&BGA meeting in Rutland, showing electron micrographs of Trichoderma hyphae colonizing plant roots and parasitizing other fungal hyphae. Unlike fungicide treatments, Trichoderma grows along with the roots, protecting them throughout the season. Early application, once soils have warmed to above 50 degrees F is important. Different formulations have been developed for seed and seed piece treatment (T-22 planter box), adding to potting mix (Root Shield) or drenching transplants (Root Shield). This is a promising bio-control product developed after 20 years of research by Dr. Gary Harmon at Cornell. Check it out.