VERMONT VEGETABLE AND BERRY NEWS, June 1, 2002
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 May 28)

(Putney) Tomatoes were slowed down by the spate of snowy and cloudy weather, but they are starting to ripen again. We picked our first lettuce today and expect to harvest salad mix next week. Cucumbers are going gangbusters.

(S. Royalton) Even with the warmer weather, we continue to slide into the ice age with frost 4 of the last 6 nights. I found that three layers of 1 ounce row cover gives frost protection to at least 22 degrees. An experiment I'd like to avoid repeating. The greens under covers continue to slowly grow but the weeds are almost non-existent. Didn't even bother planting corn till the last couple of days.  Being organic, the seed never would have made it.

(W. Rutland) Corn finally planted, squash, cukes, and all the other crops going in as fast as possible. Better crop of asparagus this year and wonder of wonders, I  am not seeing any more woodchucks. Froze my butt off at the farmers market for under 100 bucks, hope this Saturday is better.

(Plainfield NH) Just did what  would normally be considered a cardinal sin: fertilized strawberries with Nitrogen in spring  I figured between what  Mother Nature has deposited for rainfall plus what we have put on for frost control our berry beds in the last month have received somewhere between 15 and 18 inches of water. Not much N  left for the plants to chew on, I figure.  There have been other challenges this spring, like sleep deprivation. There has been no relief from frost control here (I irrigated 7 out of the last 10 nights and was up all of them worrying and checking). Bedding plant sales here are off 50% and although I expect us to narrow that up now that the weather is breaking I am not sure we will be able to make up the difference. As of May 25 we have peppers, tomatoes and watermelons out and under hoops and row cover along with the usual little stuff (10-15 days later than normal) but the temps here still dip into the 30's when they predict mid  40's. It appears as though the first planting of corn is emerging OK, even some yellow supersweet that I soaked before planting. It was planted on our sandiest ground and might be OK. We did capitalize on that cold rainy weather by getting our new strawberry, blueberry and raspberry plants in. Every cloud has a silver lining.

(Burlington) Warmth has started to help make things grow, but surprise frost in the Intervale last night (weather predicted upper 30's) nipped a few strawberry blossoms. No major pest problems, or weed problems because nothing is growing or coming out of dormancy. Looking forward to predicted warmer weather and the start (continuation) of the season in earnest (for the warm weather crops). We figure that many early plantings of lettuce and broccoli will overlap come harvest time and are trying to figure out new marketing options for the surplus.

(Grand Isle) We are harvesting asparagus, rhubarb, and wintered over spinach and parsley. The sweet williams are just starting to show some color. The cool May temperatures made the asparagus picking more even and consistent than usual. We didn't have the hot May days that cause a field to get away from us. Flea beetles found the broccoli transplants quickly. There are no other big pest problems yet. Now that we have had some great rainfall and things are starting to warm up, peas and the like should start to grow more quickly. The wildlife on the farm is beautiful in spring. Nests are being built everywhere. How does a mother robin  put up with the noise in an irrigation pump house anyway?

(Starksboro) Iím still looking for my first seeding of corn to come up. I seeded it May 8 and itís now been 18 days. So far my transplanted corn is way ahead of the seeded plantings. It has no row cover on it and has had itís leaves singed by frost 2 or 3 times but itís up and itís roots are reaching out from the original plug and thatís better than the seeded corn. Plant sales finally took off Memorial day weekend. Itís about time! Iím still waiting for the Spirea bush to reach full bloom as a sign that cabbage and onion maggots are past. We also call it the Memorial Day Bush,
and it looks like it could be right on schedule.

(Argyle, NY) Cold weather has been a challenge, but the strawberries look good after many nights of multiple row covers. The first berries are just starting to turn pink. Asparagus was frozen out last week, but is regrowing and now is being attacked by asparagus beetles. Flea beetles have been our worst pest so far on seeded turnips, radishes, etc. Harvests of lettuce, spinach, rhubarb, and radishes continue to go well. All upper fields are under full irrigation for the first time, but the heavier soils of lower fields are still drying out. Beans and potatoes are up, and the warm weather should help get everything growing faster and improve markets. Last Saturday, it snowed at the market, so things can only get better!

EFFECTS OF COLD TEMPERATURES ON CROPS
(adapted from Illinois Extension and other sources)

Cold temperatures cause stress and physiological injury because it affects growth of cells, synthesis of cell walls, respiration through leaf stomata, and photosynthesis. In curcurbits, low temperatures of 50 to 60 degrees F can may cause shorter stems and smaller leaves. Exposure below may cause white areas on cotyledons or white to light brown margins on the leaves. If severe chilling occurs, large necrotic areas can appear on the leaves and the plant may eventually die. Cucumbers are probably the most susceptible to chilling.

In tomato and pepper, cold weather may reduce flowering and flower-set. Later in the season, chilling affects the fruit, causing failure to ripen or irregular ripening, premature softening, surface pitting, brown seeds and increased decay. These symptoms are likely to appear after the cold period when the fruit is exposed to higher temperatures. Green tomatoes are more sensitive to chilling then ripe fruit. ĎCat-facingí of  tomato fruit occurs when embryonic flowers (which start forming 4 weeks after sowing for an early variety, about 2 to 3 weeks before the first clusters open) to cool temperatures around 50 F night and 60 to 65 day. Colder night temperatures are actually better in terms of how much cat facing you get as growth stops altogether.
 
In sweet corn, low temperature Ďsun-scaldí or cold banding is very common on corn that is 10 to 18 inches tall. Conditions favoring development are clear, dewy nights with temperatures of 41 to 59 degrees F, followed by sunny mornings. Symptoms appear as irregular, light gray to silvery streaks on both the upper and lower surface of the leaf. Younger corn plants can develop yellow bands on one or more leaves as a result of these conditions.

Several conditions increase the potential for chilling injury to occur below 50F,  including: 1) more time at cold temperatures, 2) lower temperatures, 3) higher-intensity light during the cold, 4) high winds during the cold, and 5) higher temperatures before the cold period began. Cool, wet soils will slow root growth and may make plants more susceptible to soil borne organisms such as Pythium spp. that cause seedling blights and root rots. In addition, wind-blown rain and soil can create wounds on leaves and spread bacterial pathogens from plant to plant. As you scout your fields remember to consider these possibilities.

TWILIGHT MEETING: MELONS & MIXED VEGETABLES FOR DIRECT MARKET
Tuesday August 20, 5-7 pm, Hurricane Flats Farm, S. Royalton

Hurricane Flats gets its name from the wind that funnels through the farm's river bottom land where for seven years Geo Honigford has been growing a diversity of organic mixed vegetables on a handful of acres. He has built up a reputation for good melons. He direct markets almost everything he grows, and except on market day, it is a lean and mean one man operation. Economically the farm has been successful, and uses a lot of hand tools along with a few tractor toys.  Directions: Take exit 2 off I-89 (Sharon). At bottom of ramp go south on Rt. 132  (from the north a right turn, from the south a left). In 100 yards go right on Rt.14. In 1/4 mile turn left, over bridge across the river, on Back River Rd. The farm is 3.5 miles up on the right, youíll see a red barn at the end of a big field.

CUCUMBER BEETLE MANAGEMENT
(adapted from UMass Vegetable IPM Message)

Striped cucumber beetles (SCB) overwinter in plant debris in field edges and with the onset of warm days and emergence of cucurbit crops will move rapidly into the field. Densities can be very high especially in non-rotated fields or close to last year's cucurbit crops. Adult feeding on cotyledons and young leaves can cause stand reduction and delayed plant growth. SCB can also spread bacterial wilt. This disease overwinters within the beetle and is transmitted by contact of beetle feces with the open wounds in leaf tissue caused by beetle feeding. Bacteria multiply and block the vascular system of the plant, causing vines to wilt.  This disease can be effectively managed only by preventing feeding by the beetle. Most vine crops are, to varying degrees, susceptible to this disease except watermelons Ė they do not show any symptoms.

Among pumpkins, two powdery-mildew resistant varieties Merlin and Magic Lantern have been shown to be highly susceptible to bacterial wilt, while other varieties such as Howden and Harvest Moon were more tolerant. Among winter squashes, buttercup, hubbard and acorn appear to be moderately susceptible, while butternut is the most tolerant (but not immune). Cucumbers are highly susceptible, except for a new wilt-resistant pickling variety called County Fair.  Summer squash, zucchini, and melons are susceptible. Different vine crops vary in the attractiveness to SCB, but this is not always related to their susceptibility to bacterial wilt.

Pumpkins at the cotyledon and 1st to 2nd leaf stage are more susceptible than older plants, and disease transmission is low after about the 4-leaf stage. The higher beetle density during early plant growth, the more severe the incidence of wilt.  Wilt development is strongly influenced by the dose of the pathogen that the plants receive. Not all overwintering SCB carry bacterial wilt. Beetles that find a host plant release an aggregation pheromone that calls others to their spot. Groups of beetles feeding, wounding and defecating on a single plant are more likely to transmit disease, and to acquire the pathogen and transmit it to other plants.

Crop rotation to a field at a distance from last year's cucurbits reduces SCB numbers significantly. Floating row covers are a very effective barrier to beetle colonization and can be kept on until flowering. Trap cropping can be used to concentrate beetles at he field edges, which can minimize pesticide use and limit encroachment of beetles into the main field. Either plant border rows with an attractive cultivar such as Baby Boo pumpkin or Dark Green zucchini (see listing of relative attractiveness at: http://www.nysaes.cornell.edu/recommends/18frameset.html)
or sow outside rows of seed a week earlier than the rest, or set out border rows of transplants at the same time the main crop is direct seeded.

Scout fields frequently (at least twice per week in June) and treat after SCB colonize the field. To prevent bacterial wilt in susceptible crops, the threshold is one beetle for every 2 plants. This is a lower threshold than needed to prevent significant foliar damage, so less wilt-susceptible crops (such as butternut) will tolerate 2 beetles per plant without yield losses. A widely used material that gives effective control is carbaryl (Sevin XLR Plus). If possible, use a banded spray to avoid wasting material by spraying bare ground.

If kaolin clay (Surround WP) is used, it should be applied before beetles arrive. This material is allowed in organic production. It can be applied to transplants before setting them out, or as soon as seedlings emerge. Ensure good coverage of the foliage (it will look like itís painted white) and reapply after a heavy rain. It acts as is a repellent and protectant, not a contact poison. The beetles do not ďrecognizeĒ the plant and so do not feed. Be sure to mix a slurry in a bucket and then add the slurry to the tank, as the dry powder could cake if added directly to the tank mix. Continuous agitation is needed. Given these precautions, it should not cause clogging of nozzles or pumps. In UMass pumpkin trials last summer, weekly applications of kaolin were as effective in preventing feeding damage and bacterial wilt as an Admire drench.

Imidacloprid (Admire 2F) has the potential to improve and simplify early season control of cucumber beetles and thus wilt. Admire can be applied to soil before or after seeding or transplanting which enables product to be in leaf tissue when an early invasion of beetles occurs.  Admire is a systemic which it is taken up by the roots, translocates to new leaf tissue and persists through the critical early plant stages. Additionally, it has a relatively safe toxicological profile.  There are several ways that Admire can be applied: as a narrow band within 2 weeks before planting,to transplants prior to setting out, as an in-furrow spray or narrow surface band during planting, as a post-seeding drench, or through the drip system. For more information on use of Admire contact me for a copy of the May 23, 2002 UMass newsletter article or get it from: http://www.umassvegetable.org/

(Mention of pesticides and name brands is for information purposes only, no endorsement is intended nor is discrimination implied against materials not mentioned. Always read the label)