June 1, 1998
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 verng@sover.net

The striped cucumber beetle is one of the most damaging pests of cucurbits, such as squash, cucumber, melon and pumpkin. The larvae can cause severe damage to roots. A single adult beetle can cause severe damage to an emerging plant by feeding on the lower surface of leaves. These beetles also spread bacterial wilt, cucumber mosaic, and squash mosaic virus. Next generation adults (over-wintering) are known to feed inside flowers, preventing pollination and fruit set.

The striped cucumber beetle is about 1/5 inch long, and has a black head and yellow?green wing covers with three black stripes. The orange?yellow eggs are laid near the base of host plants. The slender white larva grows to about 1/3 inch long and is dark on each end. There is one generation per year.

Only unmated adults over?winter. They do so in or under leaves, rotten logs or almost any other debris close to the ground. They emerge in the spring when soil temperature reaches 55 F. Then the beetles feed on pollen, petals and leaves of willow, apple, hawthorn and on their alternate hosts of goldenrod, aster, etc. As soon as cucurbits, the preferred hosts, come up or are transplanted, the beetles fly to these plants to start feeding and mating.

In a few days, the female lays eggs near host plants or in the soil. The eggs hatch in about 10 days. The larvae work their way to the plant roots where they feed for the next 2 to 6 weeks, sometimes causing severe damage. The mature larvae pupate in the soil. The adults emerge in 7 to 10 days. These beetles are not usually seen the rest of the summer except when feeding in cucurbit flowers.

Because overwintering cucumber beetles are around by the time cucurbits are up or transplanted, it is important to start scouting immediately and frequently in order to apply timely controls. Often, infestation levels will continue to increase for about 2 weeks, so although the beetles are easy to kill, more keep arriving on the plants, and it sometimes seems as though controls are not effective. Population increases can be rapid during hot, dry weather. Cool, wet weather tends to prolong the beetle feeding season. When scouting, watch for 'hot spots' along field edges, and consider treating these with a backpack sprayer instead of spraying the whole field.

Recommended thresholds for control vary. Plants are most at risk from emergence to the 4-leaf stage, when 2 to 5 beetles per plant may warrant control. Cucumber and melons are more susceptible to bacterial wilt than are squashes, pumpkin or watermelon, so using a low threshold on these crops is advisable. Once plants have 5 or more leaves, feeding is much less likely to affect yield, and only heavy infestations of leaves, blossoms, or fruit warrant treatment.

Hand-picking is an option on small plantings, and is most effective if done early in the morning when active feeding occurs. Barriers of floating row covers can protect large or small plantings, but these must be removed in time to allow pollination. Eradication of goldenrod and aster from the vicinity of cucurbits helps reduce the number of beetles. Removing plant debris after the growing season is also advisable. The 1998-99 New England Vegetable Guide lists insecticides labeled for control of cucumber beetle on cucurbits including several pyrethroids, rotenone, or carbaryl.

Church and Dwight, the company that markets Arm and Hammer baking soda, recently received EPA approval for the registration of Armicarb 100, a potassium bicarbonate fungicide. The label is for control of powdery mildew and several other diseases on a wide variety of vegetables, berries, fruit trees, woody and herbaceous ornamentals. I have been told by the company that the product is in the process of being registered for use in Vermont. The ingredients are 85% potassium bicarbonate, and 15% food-grade surfactant. Homeowner packages will be available soon through Bonide. A commercial distributor has yet to be identified. I will keep you posted.

Putting out transplants in field and rowcovering. Hail on evening of 5/21 damaged 40 % of berry crop. Too early to tell how that will play out. Bedding plant business very brisk, probably due to the favorable spring weather. Clipper controlled in strawberries with 1st spray, getting ready to apply fungicides as we enter petal fall, some TPB about although not at threshold levels. (E. Hartland)

No TPB on sticky cards in strawberries. Some cucumber beetle at field edges. (Dummerston)

First cucumber beetles seen on 5/23. Wax paper hot caps have been great for protecting field tomato seedlings from wind damage and promoting earliness. (Springfield)

Leaf miner infestations on spinach and beet greens. Will Bt work? Other organic solutions? (Shaftsbury)

No Colorado Potato Beetle (CPB) on potatoes yet, although arrived May 17 last year. No striped cucumber beetles either. First flight of cabbage maggot flies finished. Spinach is ready 2 weeks early this spring. Bedding plant sales extremely strong. (Starksboro)

Transplanting and seeding like madmen. Dry windy conditions biggest problem. Cutworm causing damage on some farms. (Hadley MA)

First CPB egg masses found (Augusta, ME)

Sunken spots on tomato seedlings, appear to be abiotic, showed up after setting plants out and cold nights followed growth in warm humid high tunnel. New growth looks excellent. Reduced price by 25 cents to $1 per plant and sales strong at farmers market. (Brattleboro)

The news on strawberries is EARLY! We'll be picking at least some fruit during the first week in June. Some change from last year when we opened on the 26th. It's also dry. We're irrigating regularly. No unusual pest problems. I've sprayed once for TPB. I'll put the last spray on in the next couple days. (New Haven)

June 9, Tuesday, 4:00 p.m. Edgewater Farm, W. Lebanon NH (A.K.A. East Hartland VT). Pooh and Ann Sprague are long time members of the Vermont Vegetable and Berry Growers. They cultivate 75 acres of diversified vegetable, berry and ornamental crops mostly for direct sale at farm stand. A lot of attention is paid to the 12 acres of strawberries, and there's about an acre of poly greenhouses. Take exit 20 off I-89 just across the river in NH, go south 4 miles on Route 12A. Turn right on River Rd. at the River Bend vet clinic, farm is 1/8 mile on left.

June 30, Tuesday, 6:00 p.m. Jack and Karen Manix, Walker Farm, Dummerston. Organic Greenhouse Production. NOFA-VT workshop call 434-4122 for more info.

July 7, John and Sue Clough, Springledge Farm, New London, NH. Info forthcoming or call UNH Extension (603) 862-3208

July 8, Wednesday, 6:00 p.m. Paul and Elizabeth Harlow, Harlow Farm, Westminster. Farming Equipment workshop. Call NOFA-VT for more info 434-4122

July 15, Wednesday, 4:00 p.m. Pomykala Farm, Grand Isle VT. Bob and Jane Pomykala grow about 30 acres of vegetables by the shores of Lake Champlain, for sale on-farm, to restaurants and at farmers market. About 4 acres of Washington type asparagus are in production, and these are being replaced with plantings of male hybrid asparagus. By mid-summer, early potato harvest should be underway. Take Exit 17 off I-89 onto Route 2 through the Champlain Islands, go approximately 12 miles then turn right onto Faywood Rd. (look for the small farm sign). Take left hand of fork in road, then farm is first place on the left.