VERMONT VEGETABLE AND BERRY NEWS - June 1, 2001
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 or vernon.grubinger@uvm.edu

Around the state, annual-bed strawberry plantings look strong. Matted rows overwintered variably in some locations despite the good snow cover. TPB adults appearing under row covered berries. Lots of lettuce getting set out. Hot weather a few weeks ago followed by cold nights made row cover management difficult - some young crops were either toasted, frozen, or both. Several growers are trying transplanting sweet corn this year. More growers are turning to Jamaican labor. Iron deficiency, bacterial wilt, leafhoppers, and nutrient-poor compost- based potting mix among problems reported in bedding plants. (Vern Grubinger).

REPORTS FROM THE FIELD (as of May 28)

Rain this week slowed field work but was really needed. Strawberries and blueberries are in full bloom with more blossoms that usual. Vegetables that are irrigated are up and growing well.  Potatoes (not irrigated) have just begun to sprout. (Springfield)

Tractors back and good as new - NOT.  Corn and beans up, cut flowers, broccoli and lettuce doing well. Viewed 15 deer in winter rye. Seems they were eye-balling the beans, sighted in old Betsy this morning. (W. Rutland)

I now know what it is like to be a grower in West Texas. Water, water, water. Things are on par with where they were last year. Absolutely no weed problems, except for where the drip line is.  Harvesting radishes, beet greens and spinach out of the field, lettuce and mesclun from the greenhouse, market sales have been booming. (S. Royalton)

We have gone to great limits to make  it rain here: yesterday we spent a gob of money on a portable  irrigation  pump and today I sprayed the strawberries and it seems to be at least drizzling as I write this. Perhaps I should have bought a larger pump to incense the raingods a bit more. We have done little but irrigate and work the greenhouses, which have done very well for us. Berries are very late, as of May 26 we are about 10% bloom without row covers which is as late as last year. Little clipper activity so far. Peppers, tomatoes, eggplants, melons, cukes and  squash are out and row covered, but little growth on anything. The last two weeks have been cloudy and cool. Even the potatoes and cole crops are skulking. I planted a greenhouse to determinate tomatoes (Red Rider and Big Beef). It had been in tomatoes and cukes for years and I forgot to  incorporate Root Shield in the medium when I transplanted them into pots. Big mistake. Big enough so I wont  make it again. (E. Hartland)

Plant sales have been strong, although I will be throwing out a bunch of Brassicas that I started too early. Strawberries are in bloom with little clipper damage so far.  Spraying Naturalis L, a fungal disease of TPB, mixed with seaweed, fish emulsion and Safer's.  Seeing the occasional adult, no nymphs yet.  I have irrigated everything I have growing twice now as we have yet to receive an inch of rain here this spring.  Hoping to set tomatoes, peppers and squash outdoors on black plastic this week, and that the last frost will skip us.(Plainfield)

In keeping with the adage: "A wet year is a disease year, a dry year is an insect year", I've been keeping a sharp eye out for insects. Scouting turned up plenty of TPB in the strawberries to warrant spraying and I'm keeping a lookout for striped cucumber beetles and flea beetles. I haven't seen any as of May 27. Soon I should see over-wintered adult Colorado Potato Beetles making their way into the new potato field. They have a tendency to just stop and congregate at the first point that they find the new field. I've heard that the adults can be flamed and I thought that this would be the perfect opportunity to use that technique. I'm going to give it a whirl. I understand that the flames must pass very quickly to avoid damage to the plants. (Starksboro)

We have received 2.4 inches of rain since May 22 . Looking for sunshine to get back to transplanting, seeding, cultivating. We'll start picking our annual bed strawberries this Wednesday. Peas are flowering. Farmers' markets are doing well and we're finally finding good help. No disease or insects problems so far except a little damage to radishes. (Argyle, NY)

We were dying for rain for 6 weeks. Irrigating just to plant. Lots of poor germination. Lots of weeds. Now it has rained for 5 days on and off. Planting continuing although some delays in field work. Prepping the squash and corn fields looks like a problem next week. We need the fields to dry out now. The worst weed year we've ever had - mostly lambís-quarters and pigweed, but some grasses as well. Second plantings of carrots, beets, greens, all doing well. Early cucurbits and brassicas fine as well. Transplanted corn on May 10. It is the best in the field. Almost 15 inches high and greening up nicely. For some reason the crows aren't pecking the direct seeded planting right next to it. I wonder if there's a correlation. Plenty of flea beetles but so far not too much more activity. Potatoes just emerging. Bugs to follow. (Amherst MA)

Here in southwestern NH, we're grateful for our first rain since early April. We had put in new plantings of strawberries and blackberries and although they have drip irrigation, they've really responded to real rain - our soil is extremely sandy. Strawberries are beginning to flower, about  5% on Honeoye and Jewel. We don't grow early varieties since they are often lost here to late frosts. Taylor and Heritage raspberries are leafing out nicely. Hope to begin planting the tomatoes and peppers next week. Saw the first sign of plum curculio on the Damson Plums on the 23rd, which is surprising given the cool damp weather. We sprayed all the plum trees with Surround (Kaolin clay) and it held on well through the rain. Last year we used clay and noticed it offered protection against the hoards of Japanese beetles in July and August. (Winchester NH)

Wonderful mix of sun and heat and rain and cool evenings has made the best spring we've had in several years.  Balance is the word.  Germination has been good for just about everything.  First cucumber beetles arrived May 25. Saw first emerging potato beetle the 24th. Trellised the sugar snap peas. First French radishes off to restaurants. Irrigation is in place but hasn't been necessary for the past 2 weeks. (Montreal)

MANAGING BACTERIAL WILT AND CUCUMBER BEETLES IN CUCURBITS
(adapted from an article by Margaret Tuttle McGrath, Cornell University)

There has been a dramatic increase in bacterial wilt, especially in pumpkin and squash. Initial symptoms of wilt are pale, wilted sections of leaves often associated with feeding injury. Symptoms of bacterial wilt progress from localized leaf symptoms to collapse of individual vines and eventually to plant death. The bacterium causing this disease cannot be controlled with pesticides, therefore, management practices target insects that harbor and vector the pathogen, the striped and spotted cucumber beetles. Control is complicated because the presence of beetles alone is not indicative of an impending wilt epidemic. In the absence of the pathogen, a much higher beetle density can be tolerated by the crop. However, if growers wait until disease symptoms occur to treat the beetles, subsequent control of wilt is erratic.

Research results show that attractiveness to beetles is not always related to wilt susceptibility.  For example, although fewer beetles per plant were observed in cucumber than in most other cucurbits, and little feeding injury was observed, a higher percentage of cucumber plants developed wilt. Muskmelon had similarly low beetle densities but less wilt than cucumber.  Compared to cucumber, zucchini was more attractive to beetles and less susceptible to wilt.  The gourd Turk's Turban was very attractive to beetles and was severely affected by wilt. In the absence of insecticide treatment, all Turk's Turban plants died before producing fruit while about 25% of the Pear Bicolored plants died by late August.

Differences in wilt occurrence were also detected among pumpkin varieties. This was not related to attractiveness to cucumber beetles or to damage from their feeding, which suggests these varieties differ in their susceptibility to wilt. A high percentage of Merlin plants developed severe wilt (at least 50% of the plant affected) by late August in both years (89-97%). Magic Lantern was also severely affected in 2000 when insect and disease pressure was higher than in 1999 (98% in 2000 versus 22% in 1999). These varieties did not have more beetles per plant or more feeding injury than Harvest Moon and Howden, in which the percentage of plants that were severely wilted was 3% and 13% in 1999 and 53% and 58% in 2000, respectively.

Waltham Butternut had fewer beetles and less feeding damage than other winter squash varieties, and it was the last to develop wilt symptoms, which were not seen until 15 Aug 2000.  It was less susceptible than Golden Delicious or Blue Hubbard; Table Ace and Burgess Buttercup were intermediate. Winter squashes Golden Delicious and Blue Hubbard had higher beetle densities, more feeding injury and higher incidence of wilt than Waltham Butternut and Table Ace.

Watermelon is considered not susceptible to bacterial wilt.  It is also less attractive to beetles than most other cucurbit crops. The pickling cucumber County Fair, which is reported to be wilt resistant, was substantially less susceptible to wilt than the other two varieties examined (7% wilted versus all Dasher II and Calypso plants wilted by 22 Aug). This was not due to differences in beetle attractiveness as there were no significant differences among cucumber varieties in number of beetles/plant or amount of feeding damage. Note: the pathogen may vary regionally so it is possible that the results obtained on Long Island may not extend to other areas.

The insecticide Admire has the potential to improve and simplify early season control of cucumber beetles and thus wilt. Cotyledons are highly attractive to cucumber beetles and susceptibility to wilt is greatest when plants are young; however, it is challenging to protect cucurbit crops with insecticides applied to leaves because plants do not always emerge at the same time in a field, young plants grow quickly necessitating frequent applications to protect new leaves, and the wide row spacing typical of vining cucurbit crop types means a lot of spray material often lands on soil.  Since Admire can be applied to soil before or after seeding or transplanting it enables product to be in leaf tissue when an early invasion of beetles occurs.  Additionally, it has a relatively safe toxicological profile. It is important to get Admire into the soil to avoid photochemical breakdown; this can be accomplished by placing it in the furrow or irrigating it in. One application of Admire at planting will not provide full-season control in all situations. Therefore, scout weekly and apply foliar insecticides if beetle counts are above 1 beetle/plant.

Practices for managing bacterial wilt organically include selection of less susceptible varieties, yellow sticky cup traps, and foliar application of kaolin clay (Surround WP).  Information on differences in susceptibility is described earlier. Sticky cup traps are yellow cups with tangle trap. They are stapled to wooden stakes and typically placed about every 20 feet along the row throughout small fields or just in the outer rows of large fields. Traps will stop working when they get covered with dust; thus they may need to be replaced once. Surround repels cucumber beetles. Replicated trials have not been conducted to evaluate Surround, partly because it is more difficult to demonstrate repellency than pesticidal activity in small plots as the beetles are less likely to leave a research field where there are untreated control plots than a production field that is entirely treated. The manufacturer based the labeling for cucumber beetles on anecdotal reports of good control. Another option is row covers. Covers provide only about 3 to 4 weeks of protection as they need to be removed by the start of flowering so that bees can pollinate.  Plants will be more lush and internodes will be lengthened compared to plants not grown under covers. Earliness is an added benefit of row covers. Trap cropping, which involves planting a more susceptible variety next to a crop, is a potential management practice under investigation.

(Mention of pesticide brand names is for information purposes only. No endorsement is intended. Always follow the label instructions).