BERRYagent - strawberry advisories for april 11

Strawberry Plasticulture Advisory Anthracnose Alert (April 11, 2002)
Vol. 3 No. 31 Barclay Poling, Editor and Extension Small Fruit Specialist, NC State

In this issue:
A. Spray recommendations for anthracnose (from Frank Louw's April 5th advisory)
B. General recommendations for minimizing anthracnose spread

A. Spray recommendations for anthracnose (Dr. Frank Louws)
A number of plantings have anthracnose present based on contaminated plant problems identified last fall. These growers will benefit >from a program that includes Quadris. Quadris does not cure infected plants nor is it completely effective at preventing fruit rot. In fungicide trials, Quadris has been found to reduce anthracnose fruit rot by about 60% once an epidemic starts. It may function as a helpful tool for growers who adopt an IPM program. Therefore, alternating Quadris with Captan, or using in a tank mix, and removing infected fruit (and plants) from the field, when practical, may limit the build-up of spores. Most growers in the southeast have no risk or low risk of anthracnose if the target pathogens acquire resistance. Resistance management is an essential component of using Quadris.

For fields where anthacnose was diagnosed in the transplants, initiate a program that includes Quadris as early as first fruit formation. Quadris should not be applied more than 2 times in a row and no more than 4 applications per season. We have posted label information in December (http://ipmwww.ncsu.edu/current_ipm/palert36.html). Under conditions of potential heavy disease pressure, our research has shown Quadris tank mixed with Captan is more effective than either product alone:

In Dr. Frank Louw's work with anthracnose fruit rot management in North Carolina (http://www.smallfruits.org/Louws.htm), he has gotten his best results by tank mixing captan ( 2 lbs per acre of active ingredient; e.g. 4lbs Captan 50WP) with Quadris (12.4 fl oz per acre). The higher rates are recommended for problem fields. Add the fungicides in 100 gallons and apply the products in a directed spray over plants until run-off. Use a high-pressure sprayer to penetrate into the plants. Frank Louws, Ext. Plant Path., NCSU, can be reached at 919.515.6689, Frank_Louws@ncsu.edu

Dr. Louw's summarized his April 5 advisory: In summary, most fungicide programs will be driven by the need to manage gray mold. If the field has a high risk of anthracnose, this disease should determine the fungicide schedule (e.g. rather than using Elevate or Switch, a grower may want to use Quadris + Captan, then Captan, then Captan + Quadris, etc.) Thus there is continuous coverage for anthracnose control and the Captan is relied upon for gray mold control. However, captan is inferior to Elevate and Switch for gray mold control. Elevate and Switch could be included with the Captan treatments but such a program becomes expensive.

Go to this address for further details on Quadris as well as other fungicides: http://intra.ces.ncsu.edu/depts/hort/berrydoc/march15/index.htm (this label indicates a Quadris rate of 6.5 to 15.4 flowable ounces per acre). This last web address has a very important fungicide table that all growers need to print out.

Other states - Quadris Label:
1. go to http://www.syngentacropprotection-us.com/labels/Index.asp?nav=SpPrdLst
2. enter your state
3. enter <Products> and select <Quadris Flowable fungicide>
4. click on the small arrow à takes you to state label (in Acrobat)

B. Four general recommendations to minimize further spread of anthracnose
If you are seeing the ulcer-like black/brown anthracnose lesions showing up on berries, or plants collapsing in the field, it is important to use all necessary precautions to keep this disease from spreading further in the field. Fungicides are an important part of the anthracnose management strategy (outlined in No. 1). But, other important measures must be taken as well to keep this disease "in-check" as much as possible.

No. 1 - Careful management of the above-ground plant environment - keep it as dry as possible meaning no overhead irrigation (hopefully, we won't need any additional irrigations for frost freeze this spring)
No. 2 - Pickers and Equipment movement of spores
a. Pickers - don't allow pickers to harvest in infected areas, and then move to non-infected areas of the field. The disease will spread on hands, clothing and shoes. Agents be very careful in responding to calls this week to have 2 or 3 sets of shoes, and additional sets of clothing to change into after visiting a site that has anthracnose, or is suspected of having this disease.
b. Equipment - don't allow equipment to move from infected areas to non-infected areas without thorough clean up first
No. 3. Roguing is the practice of removing diseased plants from a field - we have done some roguing of anthracnose infected plants at the Clayton Central Crops Research Station in years past, and if it is done early, it can help a lot! If it is not done early in the season, it will not help. This week is absolutely critical for employing this technique - a number of agents have called this morning, and in most cases, the anthracnose has just started to show up (on fruit and you can also see a number of wilting plants). We take plastic trash bags to the field and fill them up with suspicious looking plants. Not only do we remove the plants with obvious symptoms (on the fruit - black/brown ulcer-like spots; and, wilting, but we also take each plant around the infected plant as well.

example double row roguing pattern:
red x = wilted plant infected with anthracnose;
black o = removed plant not showing symptoms, but believed to be also infected
red o = rogued out wilted plant (try to get as much of this plant out of the ground as possible)
caution - be extra careful not to allow workers to touch other healthy plants

before	roguing pattern
x x x x x x x x x x x x x x	x o o o x x x x o o o x x x

We remove ALL OF THE TOPGROWTH (LEAVES, FRUITS, FLOWERS, AND CROWN). Just grab the base of the plant and give it a good twist to break off all of the top growth it is impractical to attempt removal of the roots in most cases.

No. 4. Lower nitrogen content of the plant - I would even consider cutting fertility rates by ½ . Dr. Barbara Smith, USDA Plant Pathologist, came to a Southeastern Strawberry Expo conference in late 1980s and said reducing N was an important strategy in managing anthracnose. The basic idea here is to make the plant tissue less succulent. Obviously, over-watering can contribute to the plants being too succulent as well the combination of too much N fertility and watering is deadly with this disease.

There will be more advisories on this problem later this week and weekend as additional information comes available.

E. Barclay Poling, Ph.D. and Extension Small Fruit Specialist
NC State University

p.s. I will be working away from office on mobile all Friday and next week: 919.418.9687

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