VERMONT VEGETABLE AND BERRY NEWS, September 15, 2003
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 or vernon.grubinger@uvm.edu
www.uvm.edu/vtvegandberry

REPORTS FROM THE FIELD (as of September 16)

(Starksboro) This is the field report I usually skip, just by virtue of being too busy to take time out for thoughtful reflection. Iíve just completed my last full Bt spraying for cabbage worms. Usually the weather cools off, the worms accordingly slow down and that pretty much takes care of things. I have, however, frequently kicked myself for not being a little more attentive to the broccoli and cauliflower. Iím promising myself that Iíll hit them both a couple more times to prevent a late October sneak attack.

(S. Royalton) Melons are still cranking and holding their taste, but the tomatoes are in their final stages as disease is very progressed.  Every planting of corn over lapped by a week, so I've been picking a lot of very ripe corn this year.  People raving about the taste; however, at the same time they still ask for Silver Queen (am I the only one out there that wouldn't feed that to my pigs).   Pumpkins and squash are half in the barn and the yield is OK.

(Plainfield) Nice fall so far. Cool and dry, then warm and dry, but with more rain than many other places.  I have irrigated renovated strawberries, which look great after a top dress of compost (at 15 yards per acre) and a couple afternoons of hand weeding by a crew.  Also irrigated a late carrot crop (Sugar Snax) which are filling out nicely. Fall Asian greens look good as they size up.  Pyrethrum spray worked well on persistent flea beetle population. Still putting Bt on all Brassicas, as there are lots of cabbage moth butterflies. Daikon harvest has begun.  I hope I can ship them all before they get too big.  Winter squash yields are off.  Late sweet corn a big hit. Got some red clover coming up under oats and barley for a cover crop to restore the tilth to some sandy ground. Starting to catch up on my sleep.

(Stamford) All the field tomatoes have been picked now and the plants removed from the field. Sept. 8th was the last harvest date. Eggplants and green bell peppers are still yielding but slow growing. Daytime temps are warm enough, but way too many cool nights over the past two weeks. Chile peppers were picked off heavily on the 8th also. Plants are all in flower again. We'll just have to wait and see how long they can go on for.

PREPARING GREENHOUSES FOR A HURRICANE
(Skip Paul, Little Compton RI)

This week a large hurricane is heading toward New England. My farm is a half mile from the coastline with not much between us and the sea. Dealing with the inevitable showdowns with hurricane force winds has been an obsession of mine since I built my first greenhouse. Now we have six with over 20,000 square feet. Here is some advice Iíve collected about preparing greenhouses for a powerful storm.

1.) Clean and check all the plastic inflation fans, and open their reduction apertures as the storm approaches. You want the two layers of plastic extra tight and rigid so the greenhouse superstructure moves as little as possible. Have a backup generator ready so if you loose power you wonít lose your inflation fans and then have a loose gigantic sail smashing into your greenhouse adding to its misery.

2.) Be sure all connectors are tight. As the years go by and wind storms come and go your greenhouse moves and shakes. These small movements can unwind some critical bolts that could lead to failure of major structural components. (Every time you change your greenhouse covering, take an hour to check critical bolts and points of stress. It is much easier then  when it is all clear and exposed).

3.) Don't let the wind get inside the structure. That means check that all doors are secured; check all intake and fan output louvers are locked down and can't flap open. Duct tape on the bottom three fins works well.

4.) Check your system for securing the plastic. If it fails wind will get in. Don't rely on weak twine or single strands of rope to hold everything in place; add a second rope here and there across the  run for added  security.

5.) Install diagonal wind braces during initial construction at both ends of the greenhouse. Insist that the greenhouse manufacturer make them to fit. Don't assume they will be included; it is cheap insurance.

6.) Take a minute to contemplate the environment immediately outside your greenhouse. It will do you no good to go through all these preparations of you don't notice a loose metal object like a trash can top and it gets sent through the greenhouse walls.

7.) Weíve built lean-to sheds on the north end of our newest greenhouses. They are 18' by 12' and serve many purposes: a home for furnaces and indoor oil storage, storage for chemicals and misc. pots, and most importantly they add considerable rigidity to greenhouses.

8.) We cement in every other ground post and add cement filled sonotubes to the end walls which increase greenhouse rigidity and act as anti-lifting anchors.

MANAGING SQUASH BUGS IN PUMPKIN FIELDS DURING FALL
(adapted from Frankie Lam, Perdue Univ. Extension)

Relatively high numbers of squash bug nymphs and adults can be found in some pumpkin fields.  In late season nymphs and adults that feed on the fruit can cause the pumpkin to collapse and become unmarketable.  Because adults and large nymphs are difficult to control by insecticides, the main tactics for management are early detection and control of young nymphs during the growing season and destroy their overwintering sites in fall.

For small fields, placing flat wooden boards or shingles near the plants to provide shelters for the bugs is the best tactic to manage the fall populations.  Early in the morning or in the evening when temperature is cool, check the undersides of the boards or the fruits, the bugs congregate in such places can be easily collected and crushed.  An alternative method is to put the bugs into a container with water and a little cooking oil just enough to cover the water surface.  After the bugs have drowned the contents in the container can be dumped on the compost pile.

Field sanitation is a successful strategy to manage the overwintering squash bug populations and in large pumpkin fields.  The unmated adults, including both male and female, overwinter in all kinds of protective shelters, including dead leaves, vines, stones, buildings, and dwellings.  After the crop is harvested, vines and non-harvested fruits should be removed from the field or destroyed by thorough cultivation.  Field margins should be as free as possible of rubbish, piles of leaves, boards, and other shelters. Growers should consider both the management of the bugs and the conservation of the field before making the decision of fall tillage and leaving the ground bare through winter.

No economic threshold for squash bug (or late season cucumber beetle) has been developed.  Unless large numbers are found and direct damage of the fruit is observed in the field, application of insecticides is not justified.  For insecticide management options see the New England Vegetable Management Guide.

VEGETABLE DISEASE NOTES
(adapted from UMass Extension)

Phytophthora capsici (crown and fruit rot of tomato, cucurbit and pepper) is showing up in many fields.  Sometimes, it appears in fields where host crops have not been grown for years, and it is difficult to explain how it got there.  Fields can also become infected by irrigation water, when water is pumped out of a pond that received runoff from other infected fields. Once Phytophthora is present, that field will be infected for years to come. As more fields become infected, we are going to have to figure out how to Ďlive withí this disease.  If you think you have Phytophthora, it should be confirmed by the Diagnostic Lab because the consequences for your rotation plans are serious. Other soil borne pathogens can cause crown rot and fruit rot with similar symptoms.  For example, Sclerotinia white mold causes a crown rot on peppers and tomato with white fuzzy growth (mycelia) on the stem; the small black nuggets that form (sclerotia) indicate that it is Sclerotinia -- but the lack of them does not necessarily mean that it is not Sclerotinia. Itís an expensive mistake to guess wrong on these diseases! Use the UVM Plant Diagnostic Lab Ė thatís what its there for. Call Ann Hazelrigg at 656-0493.

Cercospora Leaf Spot fungus causes widespread disease on beets, Swiss chard, and spinach wherever these crops are cultivated in the U.S. Symptoms are circular 2-5mm lesions, tan to light brown in color with darker, sometimes purplish borders. Lesions coalesce on heavily infected leaves. Outer leaves eventually collapse leaving the less heavily infected inner leaves. Extended periods of nighttime temperatures between 70-80 ?F and relative humidity of 90-100% favor disease development. Occurrence of the disease is negligible when temperatures are below 61 ?F. Because the fungus survives on crop residue infected fields should be deep-plowed and planted on a 2-3 year rotation with non-host crops. New fields should be separated from recently planted fields by a minimum of 300 feet.

Downy mildew is a common problem in broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, kale, radish, rutabaga, and turnip. Infection of host plants can occur at any growth stage Ė on cotyledons of seedlings, generally on lower leaves of mature plants,
and on the florets of broccoli and cauliflower and heads of cabbage. Lesions appear as circular or angular yellow spots on the upper leaf surface, sometimes accompanied by delicate white mycelial growth on the leaf underside. Infection on cabbage can extend to the head leaves
forming sunken black spots. Extensive bacterial soft rot may occur as a secondary infection. Disease development is favored by cool, moist conditions. Optimal temperatures promoting disease are 75 F or less during the daytime and 45-60 F nighttime, and leaf wetness lasting until midmorning for4 days in a row. Spring and fall crops are more susceptible due to lower average temperatures, with the tendency for summer crops to outgrow the disease. Two-year field rotation to non-crucifers is advisable. Avoid overhead irrigation to reduce leaf wetness periods. Cultivars of broccoli found to be resistant or tolerant are Arcadia, Cindy, Citation, Esquire, Eureka, Green Belt, Hi-Caliber, Marathon, Mariner, Pinnacle, Samurai, Sprinter, and Zeus.

PHYTOPHTHORA ROOT DISEASE OF STRAWBERRY AND RASPBERRY
(adapted from Michael Celetti, Univ. of Guelph in the NY Berry News Vol. 2 No. 9)

Cool, wet soils are ideal for infection of berry roots by Phytophthora pathogens that cause red steele of strawberries and Phytophthora root rot of raspberries. When the soil is saturated with water for sustained periods of time (30 minutes to 6 hours) these pathogens produce and release zoospore with tails that swim toward and infect berry root tips. Thatís why plants growing in heavy soils or those with poor drainage are more susceptible to infection. Infected plants frequently appear stunted during the second or third year of growth, often in patches first in low areas where water accumulates. Eventually the disease moves along the row. Red steele can be diagnosed by digging up strawberry plants and slicing them lengthwise. The steele, or vascular tissue (the Ďplumbingí in the roots) appears blood red, surrounded by white cortex tissue, although this symptom may not be apparent late in the season. The secondary roots are often pruned significantly. Infected raspberry plants produced few primocanes, and canes often appear wilted with leaves scorched along the margins, between the veins. Eventually the leaves turn yellow. Scraping the surface of infected roots will reveal reddish-brown tissue with a distinct margin where it meets healthy white tissue. The reddish tissue may extend into the crown.

The best management of these diseases is prevention through cultural practices such as resistant varieties, good site selection, and/or drainage improvement techniques like subsoiling, tiling and  raised beds. Heavy mulch can reduce soil drying and exacerbate the problem. Some strawberry varieties with red steele resistance include Annapolis, Cavendish, Earliglow and Sable. The popular varieties Honeyoe and Jewel are susceptible. In raspberries, Latham and Newburgh appear somewhat resistant. The fungicides Aliette and Ridomil Gold are available to manage these diseases, but on wet soils where susceptible varieties are grown they may not be effective.  For more information see the New England Small Fruit Pest Management Guide, hard copy from your extension specialist or on line at: www.umass.edu/fruitadvisor/

RETURN TO VERMONT VEGETABLE AND BERRY PAGE