2012 - Washington Red Raspberry Commission

Project Title: Fungicide Resistance in Botrytis in Washington Berries
2) Details of Project:
Crop/Site: Raspberry/Blueberry Chemical: Several
Pest Management Issue: Resistance to fungicides
Pest: Botrytis cinerea
5) Project Category: Check all that describe the focus of your project.
Registration ____%
___Efficacy Trial
___ Phytotoxicity Study
___ Residue Study
Non Registration: 100 %
4) Research Lead:
Alan Schreiber,
ADG, Inc.
aschreib@centurytel.net
____ Integrated Pest Management
X Resistance Management
___ Other:
6) Project Duration Start Date : February 1, 2013 End Date October, 30, 2013
7) Total Project Cost $ 11,300 WRRC Request $ 3,000
Co-funding $ 8,300
___ GLP
X non-GLP
Project Summary: Raspberry and blueberry suffer heavily from Botrytis, which has a history of
developing resistance to fungicides. Growers treat each crop three to six times per season with a
limited number of products. The number of products available is further limited by MRL and label
restrictions. The same set of products is used for its control on both crops. 2011 failures in the field
raised the specter of resistance. An internal research project of an agrichemical company conducted
in 2012 indicated that multiple fungicides may have resistance issues on raspberries. We propose to
sample raspberry and blueberry fields throughout western Washington to survey for resistance to a
range of fungicides. This information is expected to result in a revision in disease control programs
for Washington berries and may result in pursuit of emergency exemptions for both crops.
Description of Problem. Botrytis cinerea, a fungus that causes blossom blight, preharvest rot,
postharvest rot, and cane infections. On raspberry, it overwinters as sclerotia on canes and
mycelia in dead leaves and mummified fruit. Sclerotia produce conidia in spring. A moist, humid
environment is ideal for pathogen sporulation and spread. All flower parts except sepals are
very susceptible. Initial infections of flowers are latent such that the fungus is dormant until fruit
ripens. Fruit rot may be more prevalent in wet weather, in fields under overhead set irrigation
systems, or where fruit ripens in the field for mechanical harvest. Conidia can infect mature or
senescent leaves, resulting in primocane infections through petioles.
On blueberry, it survives as sclerotia (resistant survival structure) and dormant mycelium on
dead twigs of bushes and prunings. It also overwinters as a saprophyte on dead organic matter
and dead plant parts in or on the soil surface. In spring, these tissues produce vast numbers of
spores during wet periods. Spores spread primarily by wind but also by splashing water.
Cultivars that tend to retain floral structures over a long period are more susceptible. Also,
branch tips killed by low winter temperatures are easily infected. Green fruit can rot when rains
continue into the late spring and early summer. Infection is more likely on fruit that retains old
floral tissue.
This is the most treated for disease of berries in Washington with growers applying three to six
applications per season starting with a prebloom application and continuing through to harvest.
(Growers who are applying only three or four applications are probably incurring significant
economic losses from the disease.) There is no threshold for this disease. If you find it, think
you have it or are at risk of having it, you have to start a treatment program. The PNW Small
Fruit Research Center ranks it as a number one priority for research for blueberry and
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