Fruit Pest News

A weekly, online newsletter whose goal is to update Extension agents and growers of commercial tree fruit and small fruit crops

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We just completed seven consecutive days of highs temperatures in the mid- to upper-80's, unusually warm for this time of year. This weather greatly accelerated plant development and may have caused problems with fire blight in apple trees, many of which were in bloom when the warm weather occurred. Showers have been few and far between. That should help strawberry growers escape some Botrytis pressure. Many strawberry blossoms sped through the open blossom phase, at which they are susceptible to Botrytis infection. (SB)

Remember that it is still lawful to sale and distribute Benlate (benomyl) until December 31 of this year. The fungicide can be used through 2003, when the EPA expects most stocks to be depleted. The EPA will set an expiration date for the food-use tolerances when it is decided how long food containing residues of benomyl could remain in the channels of trade assuming that the last treatment occurred on December 31, 2003.

Growers of bramble crops should make an effort to locate some Benlate. The related fungicide Topsin M is not labeled for use on these crops, and there is currently no other labeled fungicide that is effective for control of anthracnose. Fortunately, help is on the way. This year alone, Elevate, Captan, and Abound are expected to receive federal registrations for bramble crops. The latter two products should have activity against anthracnose. Other fungicides are expected to be registered later. (SB)

Grapes have responded to the hot weather and are at the 1- to 3-inch shoot stage or beyond. If you have not applied your first fungicide spray yet, you need to do so. Most areas have had weather too dry for infection by the black rot and Phomopsis cane and leaf spot fungi, but that can change quickly. Furthermore, the dry weather is actually favorable for powdery mildew. Last week's high temperatures were above the optimal range (68-80 F) for powdery mildew, but were not inhibitory to the fungus (above 90 F).

Choose a fungicide(s) based on the history of disease problems in the vineyard, using an efficacy table such as the one on page 17 in the small fruit spray guide, PB1197. Sterol inhibitor fungicides can be used in the early sprays, but keep in mind that they do not provide control of Phomopsis or downy mildew. The multi-site inhibitors (e.g. captan, mancozeb, maneb, ziram) are better choices for control of Phomopsis, and they also control black rot. The sterol inhibitors can be tank mixed with the multi-site inhibitors to provide control of powdery mildew and systemic control of black rot. Strobilurins have the broadest spectrum of activity, but are more expensive and are limited to 4 applications per year.

Considering the arsenal of fungicides available to the grape grower, it is a good idea to become familiar with the classification of the products, as listed on page 34 of the spray guide. (SB)

Plasticulture strawberries have begun or are approaching harvest. Hopefully, the cooler weather will last for a while and extend the season. That weather would also suppress anthracnose, which is favored by hot, rainy weather. Anthracnose was reported last week in Alabama and North Carolina. If you see anthracnose, please let me know.

To safeguard against anthracnose, you can follow an alternation program between Quadris and captan, on a 7-10 day schedule. In severe anthracnose cases, Quadris should be applied once per week for 4 weeks during harvest. The Quadris label requires that other labeled fungicides also be used in a Quadris program, to guard against resistance developing. Use a fungicide that has anthracnose activity when rotating away from Quadris.

One strategy would be to make a captan or Switch application between each Quadris application. Captan provides fair control and Switch provides excellent control. However, Switch is limited to 55 oz per acre per year, and some of that allotment may have been used during the bloom period. Switch also has a 12-month plant-back restriction for any crop other than strawberries or onions.

Another strategy in fields in which anthracnose is a problem would be to tank-mix Quadris with captan, but the requirement of alternating to a fungicide not related to Quadris for 1 application after the second application of the tank mix must still be satisfied. (SB)

Fungicide applications for control of peach scab should begin at the shuck split to shuck fall stage, about one week after petal fall. Do not wait until all the shucks have fallen to make this application. Continue on a 10-day interval until 40 days before harvest. The most effective material is Bravo, but it is not labeled for use after the shuck fall stage. Captan, sulfur, and Abound are other peach scab products.

Shuck split is also the time to begin bacterial spot sprays on susceptible varieties. Mycoshield should be applied every 10 days until 3 weeks before harvest. (SB)

The mild winter followed by a dry spring may produce some powdery mildew conditions. A mild winter allows for good survival of the mildew-infected buds, and dry weather aids conidial germination and fungal growth of powdery mildew fungi. Watch for shoots that appear to be growing out entirely white, especially on inner, shaded sprouts. These shoots are developing from buds that were infected with powdery mildew the previous season. Fungicide protection is needed until terminal buds are set. The best mildewcides are the sterol inhibitors (Nova, Rubigan, Procure) and the strobilurins (Sovran, Flint). (SB)

**Nashville (Davidson County) Pheromone Trap Catches for 2002**
3-15 put out	OFM	RBLR	OBLR	CM
3-21	0	34	0	put out
3-25	0	8	0	0
3-26	0	5	0	1
3-27	0	0	0	0
3-28	2 biofix	0	0	1
4-1	2	13	0	1
4-2	5	12	0	0
4-3	1	5	0	0
4-5	0	0	0	0
4-8	0	5	0	1
4-9	1	5	0	0
4-11	4	5	0	0
4-12	5	0	0	0
4-15	22	7	0	0
4-18	39	3	0	0
4-19	24	0	0	0
4-22	29	0	0	0

**Bradley County Pheromone Trap Catches**
3-14 put out traps	OFM	RBLR	CM
3-15	6 biofix	67	0
3-16	6	49	0
3-17	30	18	0
3-18	38	14	0
3-23	55	21	0
3-30	14	5	0
4-6	23	5	0
4-13	46	18	1
4-20	77	23	20

	OFM	RBLR	CM	TABM
4-2	0	11	2 biofix	0
4-3	0	33	4	0
4-5	0	7	0	0
4-8	11	16	2	0
4-10	13	8	0	0
4-12	0	7	0	0
4-15	2	34	0	0
4-17	3	19	0	0
4-19	6	20	0	2

4-10 put out	OFM	RBLR	CM
4-12	2	3	0
4-19	21	9	0