Apple farmers in New York State and other eastern states must apply fungicides to their trees 10 to 15 times during the growing season to protect the crop from fungal pathogens that would otherwise destroy the crop and debilitate the trees. Apple farmers depend on university researchers for unbiased evaluations of the many different fungicide products that are labeled to protect apple trees from fungal diseases. Dr. Dave Rosenberger conducts detailed field trials with fungicides each summer and provides those results to fruit growers in New York and surrounding states. These scientific comparisons and the recommendations that are derived from them help growers to know which products will be effective for the specific diseases that are prevalent in their orchards, the rate at which the product should be applied, and the best time for making those applications. The recommendations derived from these trials are made available to fruit growers via extension newsletters and oral presentations at fruit grower meetings. Results from Dr. Rosenberger’s trials are used extensively throughout the northeast and impact spray decisions not only for New York apple growers, but also for apple growers throughout much of eastern United States.

New York produces more than one billion pounds of apples annually from approximately 42,000 acres of apple trees. New York’s warm humid summers favor development of many fungal diseases that can attack apple fruit and leaves. Farmers protect their apple trees by applying agricultural fungicides that protect trees and fruit from these pathogens. These fungicides are carefully evaluated, vetted, and labeled for use by the U.S. Environmental Protection Agency before they can be sold to farmers. However, many different products are available, each with its own strengths, limitations, disease control spectrum, and environmental impacts. Individual farmers must decide which fungicides to apply at any given time based on constraints of product costs, pest incidence, weather, apple cultivar, and the intended market for their apples. When those decisions lead to disease control failures, farmers cannot market the damaged fruit and severely affected trees may die. However, overly conservative decisions result in unnecessary fungicide applications with their contingent high costs and environmental impacts. Apple farmers therefore depend on being able to access up-to-date information on the effectiveness and limitations of new fungicides and on new strategies for optimizing use of older fungicides. This information can only be provided by conducting field trials in which various fungicides are compared under rigorous scientific standards.

Dr. Dave Rosenberger, plant pathologist at Cornell University’s Hudson Valley Lab near Highland, New York, conducts annual evaluations of new fungicides and new strategies for optimizing effectiveness of older fungicides. The research plots contain more than 1,000 apple trees from 35 cultivars. For each field test, treatments are applied to four replicated plots that contain at least two different apple cultivars. Plots are sprayed multiple times between bud break and harvest. The 18 separate field trials completed over the past two years involved 34 different products, a total of 176 replicated treatments, and 582 separate fungicide applications. Evaluations required observing more than 85,000 leaves and 65,000 fruit annually for eight different fungal diseases. In addition, 16 trials with 243 separate treatments were completed to evaluate fungicide effectiveness against apple decays that occur during postharvest storage. Results were summarized and published in 23 technical reports. Results were also incorporated into extension talks and articles that keep fruit growers updated on the latest developments. Over the past two years, Dr. Rosenberger has authored more than 40 extension articles that incorporate results from field trials. Many of these were reproduced in different newsletter series in various states. During that same period, Dr. Rosenberger also presented research results in more than 50 fruit grower and extension meetings in eight states.

USDA statistics from 2005 indicate that nearly one million pounds of fungicides are applied to apple trees in the United States each year. Apple growers need up-to-date information on benefits and limitations of the fungicides that they use so that they can optimize effectiveness of their sprays while minimizing negative environmental impacts. University research programs such as the one operated by Dr. Rosenberger provide detailed results from unbiased comparisons of various fungicides, thereby providing critical decision-making information to apple producers. Without data from these programs, apple growers would be forced to rely on manufacturer claims about product effectiveness and/or sales pitches for particular products. Currently, there are only three other university scientists in the Northeast, Mid-Atlantic, and Great Lakes States who conduct extensive fungicide evaluations. Each of these programs operates in different climatic areas and with slightly different objectives, so each program is essential for gaining a complete picture of fungicide effectiveness. By providing objective data on fungicide efficacy, Dr. Rosenberger helps growers to protect their crop while remaining economically competitive. Consumers benefit because they are supplied with a year round supply of disease-free apples at a reasonable price. Everyone benefits when farming practices are adjusted to minimize negative effects on the environment.