Vermont Vegetable and Berry News – April 26, 2006
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 ext.13,

Cary Giguere, Vermont Agency of Agriculture

Indar has been shown to be one of the most effective materials for managing mummyberry disease in blueberries, but since it is not labeled for this use many states have applied to EPA for special permission to use it. A so-called Section 18 Exemption has now been issued for the use of Indar 75WSP for mummyberry control in blueberries in Vermont. The exemption runs from April 1 to September 1, 2006. You have to be in possession of the supplemental label at the time of application. The supplemental label is available on the Vermont Agency of Agriculture web site

Indar used to be a Rohm and Haas product, but is now manufactured by Dow AgroSciences, if growers have existing stocks of the Rohm and Haas product they may be used. The recommended application rate is 2-oz per acre using ground equipment. Sprays should begin at early green tip and subsequent applications should be made at ten to fourteen day intervals. Do not make more than five applications per season or use within 30 days of harvest. Do not use any spray adjuvants with Indar 75WSP. Applications are not permitted within 75 feet of streams, rivers, ponds, lakes, or reservoirs. Carefully read the label before use.

Adapted from article by Tina Smith, UMass Extension

Pythium is one of the most common fungi found in roots of greenhouse crops. It is a natural inhabitant of the soil and can survive there indefinitely as well as in debris in the greenhouse. Stunted growth and wilted plants are common above-ground symptoms caused by Pythium root rot. To examine plants, remove plants from pots and examine roots. Healthy roots are white and firm; decayed roots may be dark colored and the rotted outer covering of the root slips from the central core.

Growers having re-occurring problems with Pythium, should review their overall production practices including fertilizing, watering and media handling. Over-watering and excessive fertilizer levels promote Pythium. Good sanitation is crucial for prevention. Keep hose ends off the floor, wash hands before handling plants and avoid contaminating growing medium.

Since symptoms can be confused with other causes such as high soluble salts or other diseases, suspicious plants should be diagnosed through your University diagnostic lab. There are several materials registered for Pythium including potassium salts of  phosphorous acid (Alude), which works by stimulating the plant’s natural defenses, and the more traditional fungicides Aliette, Banol, Banrot, Subdue, etc. Apply treatments as a drench, following label directions. After application, irrigate with additional water to move the fungicide into the root system. Note that about half of most isolates received at the UMass diagnostic lab over the past few years have been resistant to Subdue. Some growers have reported some success using a rescue treatment of hydrogen dioxide (ZeroTol) drench, followed by a fungicide treatment, the theory being that ZeroTol will knock down the pathogen in the soil and the fungicide will act as a protectant. A study is currently being conducted to determine whether growing media affects the activity of hydrogen dioxide.


Research conducted on Long Island by Dr, Meg McGrath of Cornell has shown that resistant varieties provided better control of powdery mildew than that obtained with fungicides applied to standard susceptible varieties.  PMR squash varieties currently available include: Butternut types: Betternut 401 and Bugle. Green acorn squash types:
Autumn Delight, Royal Acorn PM, Sweet REBA, Table Star, and Taybelle PM. Specialty types: Bush Delicata – elongated green fruit with white stripes. Celebration - gold striped acorn. Harlequin – green striped acorn. There are tables showing cucumber, melon, pumpkin an squash varieties with resistance to PM and other vegetable diseases at:

Pumpkin varieties listed as having powdery mildew resistance include: Aladdin, Cannon Ball, Gladiator, Gold Challenger, Iron Man, King Midas, Magic Lantern, Magician, Merlin, Mystic Plus, Neon, Oktoberfest, One Too Many, Prankster, Rockafellow, Spartan, SuperHerc, Sweet Lightning, Touch of Autum.

If Phytopthora rot has been a problem on your farm, consider growing the resistant pumpkin varieties Apprentice, Iron Man, and Li’l Ironsides.

Adapted from article by Cathy Heidenreich, Cornell University

Several cane diseases can infect raspberries, including anthracnose, spur blight, and cane blight. Anthracnose is much more severe on black and purple raspberries than on red raspberries. Symptoms appear in spring as small, purple spots scattered over young canes. These spots enlarge to about 1/8 inch in diameter, become sunken in the center, and turn gray with a purple border. Many spots can run together to form large sunken diseased areas on the cane. Infected drupelets remain small, are pitted, and slow to ripen. Leaves may also be infected and develop a “shot hole” appearance. Early spring wetting periods favor development of this disease.

Spur Blight is more of a problem on red raspberries than on black raspberries. Yield losses occur most frequently in overgrown, excessively vigorous plantings; avoid
excessive nitrogen. In mid to late summer, chocolate brown to purple blotches appear centered around individual buds on canes. Buds within the discolored areas either fail to
grow or produce weak shoots the following year. Wet conditions during early spring favor disease development. It is important to note with this disease that infections occur in early spring but do not become visible until mid to late summer.

All species of Rubus are susceptible to cane blight. It is most common in black and purple raspberries due to tipping practices. Red raspberries appear equally susceptible. Damage caused by this disease may include bud failure, lateral shoot wilt, and cane death. Dark brown to purple cankers appear on main canes or branches below wilted foliage, and may extend several inches along the cane. Cane blight is more likely to
involve whole stems than spur blight as it is not as confined to areas surrounding buds. Infection sites are often associated with pruning wounds or injuries, which may not be obvious. Cane blight infections most often occur from late April to early May.

A ‘delayed dormant’ application of lime sulfur or copper is critical where raspberry cane diseases are problematic. Liquid lime sulfur (Miller’s Lime Sulfur Solution or Sulforix) should be applied when new leaves are exposed 1/4 to 3/4 inches; if you are late in your application and don't spray until a few leaves have unfolded, cut the rate to 10 gallons per acre. Thorough coverage of the canes is essential for control so be sure this application is done on a calm day in a sufficient amount of water to soak the canes completely. A note of caution- this spray may be phytotoxic if applied after 1/2 inch green, particularly on a warm day. Alternatively, several copper products are also labeled for use as a delayed dormant spray for raspberry cane diseases. These include various formulations of both copper sulfate and copper hydroxide. A delayed dormant spray is not necessary on fall bearing red raspberries if the previous year’s canes are mowed and removed from the planting or thoroughly shredded.

Cultural practices are very important to managing cane diseases. Start with disease free plants. If you are propagating your own materials, be sure to select only disease free stock plants! Unfortunately resistant cultivars have not yet been identified for any of the 3 cane diseases, but cultivars less susceptible to spur blight include Brandywine, Killarney, Latham, and Newburgh. Particularly susceptible cultivars are Royalty, Titan, Canby, Skeena, Willamette, Reveille, and Sentry.

Promote good air circulation by keeping fruiting rows narrow, spacing canes adequately, and controlling weeds. Maintain plant health by managing soil nutrition and irrigation, and minimizing plant wounding. For cane blight management, time pruning and tipping operations to allow 4 or 5 days of healing before a rain. A fungicide application is advised after pruning in heavily infected plantings. Avoiding or minimizing the use of overhead irrigation will help limit cane disease development and spread, especially anthracnose. Reduce overwintering disease inoculum by pruning out old diseased canes before new canes emerge in the spring, then remove and destroy the debris.

Mention of pesticides is for information purposes only; no endorsement in intended nor is discrimination against products not mentioned. Always read and follow the label.