The project presently develops new fundamental and application knowledge regarding the nature and control of pathogens and diseases of onions grown on the muckland (organic) soils of New York that can be utilized by New York onion growers in enhancing their profitability.

Onions are one of the major commercial vegetable crops grown in New York. The onion industry of the state is economically competitive on a national and international basis. Onions are stored and marketed throughout the year, and this enables a continued relationship with buyers which enhances sales. There are a large number of diseases from which onions grown in New York must be protected. A continuously expanding in-depth understanding of the nature of these diseases and of the biology of their pathogens is critical for developing new programs and revising traditional programs for effective control of the diseases. Therefore, a strong continuing research program on onion diseases and their pathogens is needed to provide a continuing flow of new information on the nature of each of the major (and necessary minor) diseases as well as methods for their control in order to maintain a competitive and prosperous onion industry in New York.

(1) Muckland soils cropped to onions during 2006 in Orange County and Oswego County for population levels of Aspergillus niger (cause of black mold) indicated considerably higher levels of the fungus in the Orange County soils than in the Oswego County soils. Outbreaks of black mold continued to occur in Orange County, but were rare in Oswego County, indicating the potential annual occurrence of black mold in Orange County which has the warmer average temperatures of the two counties. Onion growers in Orange County now are advised to harvest onions during the cooler temperatures of the day and maintain good airflow through freshly harvested onions in the field and indoor storages. (2) Pristine, used alone or in combination with other fungicides in several field trials in western New York, indicated control of Botrytis leaf blight under light disease pressure from the pathogen, Botrytis squamosa. (3) The cooperative effort with Cornell plant breeders in developing onion germplasm resistant to Botrytis leaf blight from an Allium roylei source continued successfully during 2006. Several backcross generations have been completed and the progeny continue to indicate strong resistance to infection by Botrytis squamosa utilizing mist chamber and controlled field screens. (4) High levels of B. allii infection of bare-root onion transplants were detected in a number of shipments of the transplants into New York from out of state sources.

During 2006, research on black mold caused by Aspergillus niger continued to indicate the importance of seed- and soilborne inoculum of the pathogen in the occurrence of the disease in New York. After undercutting and field drying, the two cultural techniques, (1) harvesting onions during the cooler periods of each day and (2) the maintenance of good airflow through onion bulbs in field and indoor storage, will be emphasized to New York growers, particularly those in Orange County where the warmest weather in the onion growing areas of the state occurs and where soil levels of the pathogen are the highest. Fungicide seed treatments are needed to minimize the role of seed transmission of A. niger into New York onion cropping systems. Studies on fungicidal control of Botrytis leaf blight (BLB) during 2006 indicated that Pristine controls BLB and can be added to the group of fungicides that New York growers have available to combat the disease. The breeding program to control BLB has now produced good-sized advanced generation backcrosses highly resistant to BLB. Studies during 2006 again proved the role of transplant onion seedlings in introducing Botrytis allii (cause of Botrytis neck rot) into New York onion cropping systems. Programs to eliminate this source of the pathogen are being designed for application in transplant production fields. Plug transplants produced in New York were shown to be free of the pathogen and are an alternative to transplants produced elsewhere.

I presently conduct research and extension activities on onion diseases affecting the onion industry of New York.

• Dr. Alison Seyb (Plant Pathology)
• David LoParco (Plant Pathology)
• Dr. Alan Taylor (Horticulture (Geneva))
• Dr. Martha Mutschler (Plant Breeding and Genetics)
• Maire Ullrich (Orange County Cooperative Extension)
• Christy Hoepting (CCE Vegetable Program in Western New York)
• Jan van der Heide (Oswego County Cooperative Extension)
• Carol McNeil (CCE Program in Western New York)