Botector: A new biofungicide for control of Botrytis bunch rot in grapes

Botector is a new biofungicide labeled for Botrytis bunch rot control of grapes. It is based on competitive exclusion of Botrytis cinera and can be used in organic production.

Botector (Aureobasidium pullulans) is a new, yeast-based biological control product marketed by Westbridge Agricultural Products in Vista, Cal., for control of Botrytis bunch rot in grapes. The product is also labeled for control of Botrytis gray mold in strawberries and Botrytis, Monilinia and storage diseases in pome fruit and stone fruit. Botector consists of two strains of Aureobasidium pullulans, a yeast that is ubiquitous in the environment and naturally occurs on plant surfaces. Botector works through competitive exclusion in that the yeast competes with other microbes for nutrients and space, thereby inhibiting Botrytis cinerea from colonizing infection sites on the berry surface. The product leaves no residue, does not affect fermentation or wine quality, and is harmless to bees and beneficial insects.

Botector performed well in a fungicide efficacy trial in Michigan in 2011 under moderately high disease pressure (see Table 1). Michigan State University Extension specialists also observed good efficacy against foliar powdery mildew (83 percent control with Botector versus 99 percent control with Pristine fungicide) in that trial, so that would be an added benefit.

Table 1. Efficacy of dormant and seasonal sprays for control of Botrytis bunch rot in ‘Aurore’ grapes in Lawton, Mich., in 2011

Treatment, rate/A

Application timingz

Botrytis bunch rot on cluster

Incidence (%)

Severity (%)

Overall severity (%)

Control (%)x

Untreated

 

78

ay

37.8

a

29.5

a

 

Sulforix 1 gal

1

63

 b

28.8

 b

18.4

a

[37.6]

Botector 5.7 oz

 2, 3, 4, 5

52

 c

11.8

 c

6.0

 b

[79.7]

Elevate 1 lb

Regalia 2 qt + CoHere 0.25%

 2, 4,

 3, 5

 

42

 

 cd

 

5.9

 

 cd

 

2.5

 

 c

 

[91.5]

Pristine 38WG 18.5 oz

Vangard 75WG 10 oz

 2, 4,

 3, 5

 

34

 

 d

 

3.2

 

 d

 

1.1

 

 d

 

[96.3]

z Spray dates: 1 = May 9 (dormant), 2 = June 14 (bloom), 3 = June 29 (pea-sized clusters), 4 = July 18 (bunch closure), 5 = Aug. 8 (veraison), 2011
y Column means followed by the same letter are not significantly different according to Fisher’s Protected LSD test (P<0.05)
x Bracketed values denote percent control relative to the untreated check

The product has to be applied preventatively to the cluster zone to be effective. The recommended rate according to the 2(ee) label is 5 to 10 ounces per acre; 5 ounces would be sufficient under normal conditions whereas 10 ounces is recommended under high disease pressure. Up to three sprays are recommended between the end of flowering and harvest, in a sufficient spray volume to assure adequate coverage. Since the product contains a live organism, it ideally needs two days to fully colonize the plant surface it is sprayed on, so apply the product ahead of anticipated infection conditions. There is no risk of resistance development, even with frequent applications. The pre-harvest interval is zero days and the restricted entry interval is four hours.

Do not apply this product aerially or through any type of irrigation system. Ensure that the temperature of the tank-mixture is below 86 degrees Fahrenheit (30 degrees Celsius). Agitate the mixture before and during application. Use the spray mixture within eight hours after tank-mixing. Do not mix Botector with other chemicals or fertilizers during application. Avoid freezing of the stored product.

Botector is suitable for use in organic production. The product can be obtained through Hamilton Ag and Wilbur Ellis and possibly other distributors in the state and the price will probably be between $30 to $40 per acre at the 5-ounce rate.

Dr. Schilder’s work is funded in part by MSU‘s AgBioResearch.

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