August 1, 1998
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967


Crop conditions are variable around the state depending on location, soil type and the time of planting. Crops on sandy soils weathered the rains best but now are requiring irrigation and are most likely to show nutrient deficiencies due to leaching. Common deficiencies are of nitrogen (yellowing of older leaves) and potassium (dead tissue along edges of middle-age and older leaves). Weeds have taken off in fields where cultivation was delayed. Some growers resortng to mowing or weed wacking. Foliar diseases are abundant due to prolonged infection period during rains. Remember that fungicides only protect healthy tissue, so plan any sprays accordingly. Many late season plantings going in - a lot of growers are hoping to make up for losses so far - here's to a long spell of normal weather and a late fall frost. (VG)

Cole crops: Imported cabbage worms plentiful, sprayed Bt. Waiting 2 weeks between sprays is often possible in July, except on broccoli. August and September require weekly scouting to determine spray needs. Potatoes: sprayed for potato leafhopper. CPB largely all done. Still protecting against foliar disease with Kocide. Tomatoes: Tom?Cast has been predicting fairly high disease potential, and I have been spraying with Kocide as frequently as every 7 days. My experience from previous years is that as nights cool off in August the disease potential will decrease and the spray interval will drop to 10 days to 2 weeks. Carrots: Seeing some alternaria even in the less succeptible varieties. (Starksboro)

A problem with basil wilting has been solved with increased spacing and full time drip irrigation. Greenhouse basil is being gobbled by grasshoppers, I have applied Nolo-Bait (a biological control) and garlic barrier. Transplanted toads and snakes, even imported a nephew from Wisconsin to collect grasshoppers with a shop?vac. Any further suggestions would be helpful. Anyone know of a market for basil finished grasshopper? Maybe chocolate dipped or marinated in fine olive oil. Cilantro in the field was doing fine until local woodchucks acquired a serious addiction. Full time effort on woodchuck patrol with the .222 and a 3x scope. Good crop and strong market for 3" herb pots and packs, especially basil, rosemary and parsley. (Thetford Center)

Aftermath of the wet conditions ? root systems diseased in wet or previously wet areas. Field corn beginning to tassle ? often corn is pathetically short (from poor roots, lack of N...) so yields are likely to be very low. Al Gotleib, UVM Plant Pathologist, is expecting mycotoxin problems this year because of plant stress. So far I have found no alfalfa fields with over threshold levels of Potato Leaf Hopper. (Sue Hawkins, Champlain Valley)

Our pumpkins and winter squash made it through the rains with about a 25% loss... not as bad as we anticipated. Now we have several hatches of baby squash bugs appearing. (Charlotte)

Downy mildew on lettuce and onion, purple blotch on onion. (Westminster)

First corn earworm moth caught in pheromone traps. Signs of armyworm feeding but no trap catches. Second generation European corn borer is here. Rust is rather extensive this year, aphids too in some places. (Ray Pestle, CT River Valley)

Leaf mold (Fulvia fulvia) is being seen rather frequently on greenhouse tomatoes where susceptible cultivars are grown. Reduction of humidity is key to managing, but control is difficult if not impossible with highly susceptible cultivars. Growers seem to try them just once....

Blueberry crop is awesome. Canes bending over with weight of fruit in some cases. Infestation of blueberry maggot reported.

Other problems observed around the state: bacterial leaf spot on pepper, leaf scorch and powdery mildew on strawberries, white mold (Sclerotinia) on beans, white flies in greenhouse tomatoes, early and late blight on potatoes, leafhopper damage on potatoes, spur blight on raspberries.

Early August is a good time to sample healthy leaves for foliar analysis of nutrients. Collect at least 50 leaves per sample, remove petioles, wash gently and allow to air dry. Put in paper bag and mail to testing lab of your choice with payment. Strawberries: first fully expanded leaves after renovation. Raspberries: non-fruiting canes. Blueberries: any healthy leaves.

This insect is an occasional pest of commercial pumpkin and squash plantings, rarely a problem in other cucurbits. The adults and nymphs suck sap from the plant causing small yellow specks on leaves and stems. Heavy feeding causes leaves to turn brown, then black and die. Later in season, once foliage has died back, feeding on fruit is more likely and can lead to spotting and possible collapse. Early control of nymphs is important before population increases and becomes protected by thick canopy and thus difficult to control. Midwest texts suggest threshold for insecticide spray is one mass of orange-bronze eggs per plant at flowering. It takes about 10 days for eggs to hatch, then 4 to 6 weeks to go through 5 nymphal instars to adult. Small nymphs are easier to control than large nymphs or adults. Nymphs present in late fall will freeze, adults can overwinter in debris and hedgerows and survive to initiate next spring's infestation. Insecticide sprays must penetrate the canopy to be effective. Pyrethroids are suggested for control, but these will kill natural enemies as well, which often provide significant control. Organic growers can use pyrethrins. Some neem products are also labeled but these will be likely provide effective control only on small nymphs. Carbaryl (Sevin) is also labeled, but avoid using WP formulation during flowering since the dried residue can be taken back to bee hives. The XLR formulation is safer, applied early morning or late night when flowers are closed.

You might be interested to know of a web site with a lot of information on pests. The site is: http://www.hcs.ohio? It is a great site because it searches pest factsheet databases nationwide. I highly recommend it. However, whenever I send out information from other states or countries, I stress that the spray recommendations must be reviewed with local guidelines, as pest life cycles and pesticide regulations may vary from state to state. (Margaret Skinner)

I recently traveled around Vermont with Dr. Mark Hoard, field entomologist with Mycotech, which makes Mycotrol and Botaniguard, Beavaria bassiana bio-insecticides for field and greenhouse use, respectively. Learned a few things: Mycotrol will hopefully have a northeast distributor soon (for next season?). A new formulation is a wettable powder that is easier to use that the current emulsifiable suspension. Also, an organic formulation that has a vegetable oil rather than a mineral oil carrier is being developed. One exciting use of Beavaria is in combination with Bt for control of potato beetle larvae. Beavaria is more effective on the large larvae, while Bt is more effectve on the small larvae. In the greenhouse, early and frequent applications of low rates of Beavaria is suggested to maintain a continuous supply of viable spores on the leaf surfaces.