BLUEBERRY BUD FREEZE INJURY NOTES
Sonia Schloemann, UMass Extension
Early last week the overnight air temperatures around the state reached very low levels. The lowest temperatures seem to have been in the northern Berkshire and northern Worcester Counties where some locations were in the single digits. Warm weather in March pushed blueberry bud development to bud swell in many locations and some varieties were approaching tight cluster. Once buds move out of full dormancy they are much less tolerant of low temperatures. See chard below from Michigan State University for critical temperatures.
Figure 1. Blueberry bud early development and critical temperatures (credit: Michigan State Univ.)
Blueberry buds samples in Western MA mid-week showed potential for significant damage (approximately 40%). It is too early to predict impact on yield because evaluating whether remaining tissue will survive and possibly compensate for lost buds. However, checking your buds can help you prepare for the potential for crop loss. See images below for examples of low level damage and high level damage to blueberry buds. More on this next time....
Figure 2. Blueberry bud freeze injury; left, low freeze injury level; right, high freeze injury level.
Mummy Berry ID and Management
Sonia Schloemann, UMass Extension
The first symptom of this disease is browning along the major leaf veins on newly emerging leaf clusters. The leaves wilt quickly and bend to resemble a shepherd's crook. A light gray powdery layer of spores develops at the leaf base. These spores go on to infect flowers and fruit. Infected green berries appear healthy but cutting them open reveals a white fungal growth inside. When berries start to ripen, infected berries appear pinkish tan and slightly ridged. They feel rubbery and contain a gray to black fungal mass inside. Infected berries eventually become faded, shrivel up, and fall to the ground. After the fruit skin has weathered off, the berries look like tiny black pumpkins.
The fungus overwinters in the mummified fruit on the ground. In early spring, trumpet-shaped mushroom cups produced on the mummies eject windborne spore that infect young shoots. Frost may increase susceptibility of blueberry shoots to infection. Spores are produced on blighted shoots and are carried to flowers by wind, rain, and insects (bees), resulting in fruit infections. Mummies that fall to the ground provide inoculum for the disease in the following year.
photo credits: 1) MSU Blueberry Facts 2) eXtension fact sheet 3) NC State Fruit Consortium
Damage: The fungus infects and invades the developing fruit rendering it unmarketable.
Consult scouting records from previous years to determine if build-up of this disease is indicated. Monitor weather conditions to identify likely infection periods. Scout fields beginning at budbreak for symptomatic tissue. This timing often coincides with Fortsythia bloom.
- Plant resistant varieties whenever possible. Those that are most resistant to the shoot blighting phase of the disease include Bluejay, Darrow, Duke, Elliot, and Toro. Cultivars that are consistently resistant to the fruit infection phase include Northsky, Reka, Northblue, Bluegold, Bluejay, Weymouth, and Patriot. Resistance to fruit infection appears to be unrelated to resistance to shoot blight, and weather factors can also affect cultivar response to the disease.
- Prune bushes to open the canopy to light, air, and spray penetration.
- Cultivate beneath plants in fall and again in early spring to disrupt overwintering inoculum.
- Apply a 3-4” layer of mulch material over the soil surface in early spring before mushroom cups emerge to create a physical barrier to spore release.
Summary Management Table:
- Apply recommended fungicides at budbreak if scouting and weather monitoring indicate risk of infection.
- Time fungicide applications closely to frost/freeze events that predispose tissue to infection.
- Repeat fungicide applications at recommended intervals if weather conditions are conducive to infection.
- Rotate fungicide materials from different FRAC groups to avoid promoting the development of resistant strains of this disease.
||Organic (OMRI Listed)
|Abound F, 6.2-15.4 oz (0 day phi; Note caution regarding spray near or with equipment also used in apples)
Captec 4L, 0.75-1 qt (0 day phi)
Indar 75WSP, 2 oz (30 day phi)
PropiMax EC, 6 oz (30 day phi)
Quash, 2.5 oz (7 day phi)
Quilt Xcel, 14-21 oz (30 day phi)
Switch, 11-14 oz (0 day phi)
|⊗ Actinovate AG, 3-12 oz (0 day phi)
⊗ Double Nickel 55, 0.25-3 lb (0 day phi)
⊗ Regalia, 1-4 qt (0 day phi)
⊗ Serenade Max, 1-3 lb (0 day phi)
| • Use resistant varieties
• Prune for open canopy
• Cultivate beneath plants after
harvest to disrupt inoculum
• Mulch in early spring to cover mummies
|Read labels thoroughly for application rates and restrictions (REI, PHI, etc.)
* Restricted Use Material
⊗ OMRI Listed
WINTER MOTH UPDATE
Heather Faubert, URI Cooperative Extension
Not many caterpillars have been found in tree buds, except one crabapple tree in Kingston where I found one caterpillar in every other flower bud cluster today. Caterpillars are tiny and difficult to find at this time. Don't bother looking for caterpillars now! Wait another week or two until caterpillars are bigger and easier to find.
Did cold weather this past week kill caterpillars? I don't think so, at least not in Washington County. I will check more locations next week. The cold temperatures did kill some apple and blueberry flower buds, but didn't destroy the crop.
Now is not the time to spray to control winter moth caterpillars.
SPRING TWILIGHT MEETINGS
These twilight meetings will focus on Apple production but will include information on Blueberry Winter injury evaluations and Mummy Berry management. Pesticide credits awarded.
19-April, 2016 (Tuesday) Fruit Twilight Meeting at UMass Cold Spring Orchard, 393 Sabin St., Belchertown, MA. 5:30 PM. 1 pesticide credit will be offered. Light dinner will be served. $20 meeting fee. Contact: Jon Clements, 413-478-7219. Pre-registration is not necessary.
20-April, 2016 (Wednesday) Fruit Twilight Meeting at The Big Apple Farm, 207 Arnold St., Wrentham, MA. 5:30 PM. In cooperation with Rhode Island Fruit Growers' Association. 1 pesticide credit will be offered. Light dinner will be served. $20 meeting fee. Contact: Jon Clements, 413-478-7219. Pre-registration is not necessary.
Archived IPM Berry Blasts are available at the UMass Extension Fruitadvisor website.
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