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Fungicide Selection for Botrytis and Anthracnose Fruit Rot Management

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Guide for fungicide use when using the Strawberry Fruit Infection Tool:

Low Risk for Both Diseases: no action required; save money and time.

Moderate Risk for Both Diseases: Be prepared to put on a protective fungicide like captan if no spray was applied in the last 7-10 days.

High Risk for Botrytis and/or anthracnose – see guidelines in the SE Strawberry Integrated Pest Management Guide.

This is a supplement to the Strawberry IPM Guide. Carefully read pages related to fungicide resistance and selection in the IPM guide.

Fungicide Selection for Botrytis and Anthracnose Fruit Rot Management
Management of Botrytis fruit rot (BFR) and anthracnose fruit rot (AFR) caused by “Colletotrichum acutatum” has become more complex. Growers need to use
products that work against resistant strains of BFR and manage AFR.

We developed tables to help with the decision process (see tables in SE Strawberry Integrated Pest Management Guide).

One table shows our current understanding of the efficacy of fungicides
for the Southeastern US (north of Florida). Efficacy in the table is indicated as
follows: E = excellent, VG = very good, G = good, F = fair, P = poor. A large
number of farms are experiencing problems with Botrytis strains that are
resistant to one or more fungicide. (Color codes match the codes in the MyIPM
App).

BOTRYTIS CONTROL: Botrytis cinerea historically has a high potential to
develop resistance. Therefore, it is important to give these recommendations
serious consideration:
1. If a Botrytis spray is needed before bloom (e.g. to control Botrytis crown
rot) use Rovral (FRAC 2).

2. **Use members of any FRAC group (except M03 or M04) no more than
twice per season.** (For example, if you used Fontelis once and Merivon
once you maxed out the 2 applications for FRAC 7 fungicides.)

3. Resistance profiles vary from farm-to-farm. Sample BFR populations for their resistance profile through the University of Georgia

(https://site.caes.uga.edu/alimdl/fungicide-resistance-testing/ for a fee).

Based on samples submitted to the University of Georgia, the Fungicide Decision Management Table (In the IPM Guide)  shows a decision guide to manage BFR. If you do not know your profile, it is best to avoid over-reliance on products where resistance is prevalent. If in doubt, follow Decision Code E-1 (in strawberry IPM Guide) since this will address the most common resistance issues for BFR control. If you also have FRAC 11 resistance for AFR, follow Decision Code E-2.

4. Specific plant sources may be identified as having AFR infestations. In that case growers need to manage both BFR and AFR.

AFR CONTROL: Resistance to FRAC 11 fungicides (e.g. Abound, Cabrio, Luna Sensation, Merivon, Pristine) has been found in Florida, North Carolina, and
California; problems tend to be plant-source associated. Therefore, it is a good idea to use the FRAC 11 fungicides only in a mixture at the lower labeled rate with the
higher labeled rate of captan products (e.g. Captan; FRAC M04) alternated with captan alone. If you know the resistance profile, see the Fungicide Decision
Management Table below. Also, recently, we have documented reduced activity with azoxystrobin (e.g. Abound, etc.; FRAC 11) with certain strains of the AFR
pathogen. Cabrio (FRAC 11) and FRAC 7 + 11 products have offered better control of AFR in recent research efforts and if the strains are not resistant to FRAC 11
fungicides.

FRAC 7 + 11 products can be used if your resistance profile shows the FRAC 7 component is still effective against BFR. If FRAC 7 resistance is diagnosed or you
don’t know, we recommend using Cabrio (plus captan). Like BFR, our data shows early bloom sprays are also critically important for AFR management.

For cases when there is no anthracnose and growers need to focus on Botrytis control (most fields), follow Decision Code A (IPM GUIDE).

Options: For a reduced fungicide program, initiate applications at FIRST bloom as above, but apply subsequent sprays before predicted wet weather that favors
Botrytis; end applications about 26 to 30 days before expected final harvests. Increase the time between spray applications when dry weather persists. Research trials have documented that 4 sprays during bloom often are sufficient to offer season-long BFR control. Also, consult available forecasting models linked through the Strawberry IPM guide.

For cases when anthracnose is present and there is no known resistance within the Botrytis population, follow Decision Code B-1.

Before predicted periods of cool and wet weather during bloom, use Switch (FRAC 12 + 9) for better Botrytis control. Use Switch with captan if Botrytis pressure is
expected to be heavy. Switch also has decent anthracnose control. FRAC 7 + 11 products or Cabrio show the best efficacy against AFR under high anthracnose
pressure in research studies and either can be used if there is no resistance to FRAC 7 fungicides (an active ingredient in FRAC 7 + 11 products). Also, if weather
conditions (warm & wet) favor AFR or you start to approach the upper limit of FRAC 11 fungicides allowed (4 to 5 applications), consider rotating to a tank-mix of
captan + Tilt (FRAC 3).

Consult the rest of the Strawberry IPM guide for additional information on total IPM Programs and download the MyIPM-SED app to learn more about disease/pest management and FRAC codes. Also consult the Diagnosis Tool (https://diagnosis.ces.ncsu.edu/strawberry/) and Strawberry Disease Factsheets
(https://strawberries.ces.ncsu.edu/strawberries-diseases/) for additional information and assistance in identifying diseases.