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dimethomorph (Acrobat)
Letter - Describing Need to Manage Phytophthora Blight 4/03

College of Agriculture and Life Science
Long Island Horticultural Research and Extension Center
3059 Sound Avenue Riverhead, NY 11901
Telephone: 631727-3595
Fax: 631727-3611

April 4, 2003

Ms. Jeanine Broughel
Pesticide Product Registration Section
Bureau of Pesticides Management, 9th Floor
NYS Dept. of Environmental Conservation 625 Broadway
Albany, NY 12233-7254

Dear Ms. Broughel,

    I am writing to describe the need for the fungicide Acrobat 50WP for New York vegetable growers to manage Phytophthora blight in some cucurbit crops. BASF, the registrant of Acrobat, has prepared a Special Local Needs label for this use in New York. I fully support this label. I submitted Section 18 requests for this fungicide in 2001 and 2002 to control Phytophthora blight (Phytophthora capsici) on cucurbit crops in New York. Both requests were granted. Acrobat 50WP received a federal section 3 registration in early November 2002 for cucurbit crops, bulb vegetables, and lettuce.

    Phytophthora blight has been causing substantial losses in cucurbits in New York since the early 1990s. Symptoms include seedling damping-off, leaf spots, foliar blight, root and crown rot, stem lesions, and fruit rot. Losses experienced by some growers have been so great to justify applying for disaster assistance. Phytophthora blight was cited as the most important disease by some growers attending the Cucurbit Crop Workshop held March 2001. Some growers question whether they can afford to continue to grow this crop if an effective control program is not developed soon. Phytophthora blight is spreading in New York and elsewhere in the United States, appearing on new farms as well as in previously unaffected fields on a farm that has experienced blight. It was first observed on Long Island and in the Capital District, then in western New York, and within the past few years in central New York. With the pathogen now established in central New York, it is poised to spread to farms throughout the state.

    All cucurbit crop types are susceptible. There are approximately 300 A of muskmelons, 3900 A of cucumber, 3500 A of summer and winter squash, and 6700 A of pumpkin grown in New York. Without an adequately effective control measure for Phytophthora blight, New York cucurbit growers will continue experiencing significant yield losses. In Suffolk County, Long Island, disaster assistance was sought because of Phytophthora blight affecting cucurbits by 1 grower reporting 87% loss in 1989, 3 growers reporting 63-98% loss in 1991, and 13 growers reporting 43-99% loss in 1992. This loss is expected to increase as more fields become infested with the pathogen. If conditions are highly favorable for disease development, all fruit in a field could become affected. Crop failure can also occur with a lower proportion of affected fruit as growers often abandon such fields because it is not economical to harvest just the healthy fruit due to the extra labor involved, and because infected fruit that do not have symptoms at harvest could develop symptoms in transit, leading to load rejection. The greatest impact is on pumpkins. Additionally, pumpkin acreage has increased substantially in New York recently because of strong local demand and increased opportunities to ship outside the region. This crop in 2000 was worth $26.3 million for 1.14 million cwt harvested from 5700 acres. Pumpkin is ranked 2 of the fresh-market vegetables grown in New York. And New York is ranked 2 in pumpkin production in the United States.

    Phytophthora blight is a difficult disease to control, thus cultural management practices alone have not been adequate. Phosphonate fungicides are registered for managing Phytophthora blight on cucurbit crops, but fosetyl-Al (Aliette) has not provided adequate disease control in replicated fungicide efficacy experiments conducted at Cornell University and at other public institutions in the United States.

    Please do not hesitate to contact me if you would like to discuss this matter or if you need anything else from me.

Sincerely,
Margaret Tuttle McGrath
Associate Professor
Department of Plant Pathology
e-mail: mtm3@cornell.edu

cc: Jeffrey H Birk
William G. Smith, Pesticide Management Education Program (PMEP)