Wild Blueberry Fact Sheet

MONILINIA BLIGHT (mummy berry)

1. Funginex 190EC**, 1.7 L/ha - 60 days*
2. Topas 250E, 500 mL/ha - 60 days*

The first spray is applied when flower buds are opening and leaf buds show 2-5 mm green tissue (40-50% V2 & F2). A second spray is applied 7-10 days later. During some seasons experience has shown that one application may provide adequate control. Correct timing of the first spray is critically important for good control. Bud development differs greatly from one area to another, so growers must take the time to inspect their own fields and have the fields sprayed at the proper time. Research indicates that if the two Funginex or Topas sprays are applied properly, good control of blight will be achieved for the entire season.

Growers using mist blowers should spray strips not greater than 15 meters, under calm conditions. Funginex moves rapidly into the plant (within one hour). Therefore it may be applied within one hour of an expected rain. Although not tested, Topas is expected to have similar activity. Funginex and Topas will provide control if applied up to 72 hours after an infection period has started. Refer to the Monilinia blight of lowbush blueberry factsheet for information on post infection control strategies.

BOTRYTIS BLIGHT

Botrytis blight occurs during bloom and may be a continual problem in some fields or in seasons when extended wet periods occur during bloom or shortly after petal fall. If Botrytis is noted in a field or the field has a history of this problem, use one of the fungicides listed at mid-bloom to late-bloom and thereafter as required.

1. ferbam 76WDG** 2.25 kg/ha - 40 days*
2. Easout 70WP 1.1 kg/ha - 60 days*
3. captan 50WP 3.25 kg/ha, captan 80WP 2.25 kg/ha, captan 80WDG 2.0 kg/ha - 2 days*
4. Maestro 75DF 2.4 kg/ha - 2 days*

Research findings indicate that the fungus overwinters on infected weeds within and outside the blueberry field. Weeds that have been observed to be sources of disease are blackberry, wild strawberry, pearly everlasting, Potentilla, narrow leafed golden rod, rough golden rod and especially sheep sorrel. During periods of wet weather, the fungus produces spores on the overwintered diseased tissue and are wind blown to developing blueberry blossoms.

Wet periods are necessary for infection and the length of time required for infection varies with temperature. As the temperature increases to 20^oC, less time is required for infection. At 4^oC, low levels of infection may occur after a 24 h wet period but at 16^oC, only 6 hours is required for low levels of infection. At 12^oC, high levels of infection occur after a 24 hour wet period, but at 16 and 20^oC, only 13 and 10 hours of wetness, respectively, are required for high levels of infection. Obviously, the greater the number of favorable wet periods that occur prior to and during bloom, the more serious Botrytis blight will be.

Early clones may be the first to become infected because they come into bloom first. Flowers become susceptible just prior to opening. At full bloom blossoms are very susceptible. Once the fungus becomes established on early flowering clones, they serve as a source of infective spores for later flowering clones. Growers should monitor the weeds, especially sheep sorrel and early flowering clones for Botrytis infections. Weed infections can usually be observed in early-mid June (in Parrsboro which is considered a later area). Shortly thereafter infections may be seen on blueberry blossoms. It is possible to observe the buildup of the disease. If the disease is evident at mid-bloom and favorable wet periods for infection are predicted, then a fungicide should be applied prior to the wet period. Further sprays at 7-10 day intervals may be necessary, depending upon the weather. Growers using mist blowers should spray strips not greater than 15 meters, under calm conditions.

Tolerance of the Botrytis blight organism to Easout has resulted in failure to control in a few areas in the province. It is therefore suggested that Easout be tank mixed or used on an alternating schedule with either ferbam or captan. It should be noted that when tolerance begins to build up, tank mixing or use of an alternating schedule will only slow down this process. If it is known that Botrytis tolerance to Easout has occurred in your field or in a field in close proximity, ferbam, Maestro or captan should be used. If tolerance is suspected in your field, contact your extension service.

* indicates the interval to harvest during which the fungicide must not be applied.

** WDG water dispensable granule; DF dry flowable; WP wettable powder, EC or E emulsifiable concentrate.

Prepared by:
R.W. Delbridge, Plant Pathologist
Nova Scotia Department of Agriculture and Marketing

P.D. Hildebrand, Plant Pathologist
Agriculture & Agri-Food Canada
February 1998

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