March 15, 1998
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967

1) Start with vigorous, pathogen-free seed. Old seed that's slow to germinate may be more susceptible to damping-off than fresh seed. If possible, buy hot-water treated pepper, cole crop, and tomato seed to protect against bacterial leaf spot, black rot, and bacterial canker, respectively. Or, you can hot-water treat your own seed - an article in the January 1998 issue of Grower explains how - call my office if you need a copy.

2) Use high quality growing media. Whether you are using "soil-less" peat-based mixes or compost plus peat mixes, if you have any doubt about the quality of your mix, conduct a bioassay and/or send a sample to the UVM Ag Testing Lab for analysis (Hills Building, Burlington VT 05405-0082). Ask for the "saturated media extract" test, and include $25 per sample. The regular "field" soil test is not appropriate for analyzing high-organic matter potting soils.

A bioassay is just an early test planting of oats, cress or another sensitive crop using your potting mix. Testing several crops is advisable to be on the safe side. This can be done in the kitchen - the plants don't need to grow too for long in order to see if the mix is good for starting transplants. However, to finish transplants, most potting mixes require that some fertilizer charge be added. The lab analysis will provide insight into nutrient availability in the mix, as well as the pH and the level of soluble salts.

3) Apply biological inoculant. There are several products on the market that contain beneficial microbes that have the ability to suppress damping off organisms. Early colonization of seedling roots by the beneficials is critical to their ability to suppress diseases and improve plant performance. Microbial products labeled for treating soil-less mixes or drenching vegetable transplants include "Root Shield" (contains Trichoderma), "Soil Guard" (contains Gliocladium), and "Bac-Pack" (contains Bacillus and Pseudomonas). BioWorks (315-781-1703), Griffin Greenhouse (508-851-4346), and Peaceful Valley Farm Supply (916-272-4769) are suppliers, respectively.

4) Strive to optimize growing conditions. Be sure heating and cooling systems are working properly, and that temperatures are adequate and uniform throughout the greenhouse. Install (additional) horizontal air flow fans to mix air if necessary. Check that heater vent pipes are securely attached and unblocked, that thermostats and therm-alarms are properly set and functional. Examine output from drip irrigation system at several locations.

5) Practice sanitation. It is easier to sanitize surfaces that have been cleaned of coarse residues. Wash excess soil and plant matter off with water or even better use an alkaline cleaning agent such as TSP (trisodium phosphate) followed by water. Then treat all plant containers, growing surfaces and crop handling tools with a sanitizing solution, letting stand for a half hour before rinsing. To make a large batch of sanitizing solution, add 1 pint of household bleach to 50 gallons water. Then mix in 2 pints of distilled vinegar to lower the pH of the solution to between 6 and 7. Otherwise, at a higher pH, the bleach solution will not be a very effective germicide. Do not acidify the solution more than recommended, as it will become corrosive at a pH below 5, and can release toxic chlorine gas below pH 4.

6) Take an IPM approach. Monitor crops closely and frequently. Place sticky yellow cards among plants as an early warning system for insect pests. Examine both sides of foliage for signs of insects or diseases. Order the appropriate biological controls at the very first sign of insect pests such as aphids or whiteflies. Once pest populations are high, biocontrols are less likely to provide control. Suppliers of predators and parasites for greenhouse pests include: The Green Spot (603) 942-8925, IPM Labs (315) 497-2063, Gemplers (800) 437-4883, Koppert (313) 998-5589.

A different kind of program will be offered for established greenhouse tomato growers on Wednesday, April 8, from 10 am to 3 pm at the South Royalton House in S. Royalton. A roundtable format will be used to allow growers to interact with specialists and each other. Short presentations by the panel of "experts" will kick off the discussion. Resource people that will attend include: Gillian Ferguson, Greenhouse IPM Specialist, Ontario Ministry of Agriculture; Rich McAvoy, Greenhouse Specialist, University of Connecticut; John Bartok, Greenhouse Engineer, along with experienced growers: Jake Guest, Jack Manix and Tim Taylor.

Pre-registration of $40 includes lunch. Send check payable to UVM Extension to Ann Hazelrigg, Hills Building, Burlington VT 05405-0082 by April 1st. Registration at the door will be $50. Directions: from the north, take exit 3 off I-89 to route 14 to S. Royalton. The South Royalton House is on the southwest side of the green. From the south: take exit 2 off I-89 to route 14 to S. Royalton.