By Marcia Anderson
Apples are susceptible to fungal spores that can blemish the fruit and cause economic harm to the growers.
Apple growers battle pest problems on a continual basis. To pests, such as moths, mites, and fungi, an apple orchard is a place to eat or a place to reproduce. Because the ecology in every orchard is different, pest conditions and circumstances are different for every grower, so controlling pests using Integrated Pest Management (IPM) makes sense.
IPM has become more and more engrained in apple pest management in the northeast over the past 30 years because most northeastern growers live right on their farms. It is in their best interests to keep the land and water as clean as possible. Apple growers have found the most effective way to control their pests is by using scientifically-based IPM practices that have positive long-term effects on their orchards.
Growers monitor their orchards weekly from the beginning of spring through the entire growing season to determine pest pressures. The growers and crop consultants become intimate with their location, learn about past disease and pest pressures, and learn the ecology of their orchards. Admittedly, they learn something new every year.
There is also an economic impact when farmers use IPM. They stand to reduce their two highest bills – chemicals (pesticides and fertilizers) and fuel – when they follow the five components of IPM. These components are: 1) prevent pests; 2) identify the specific pests present; 3) set economic thresholds for each pest as a decision making tool; 4) monitor for pests and their damage, and; 5) use a combination of management tools.
Maintenance and sanitation are key parts of preventing pests in apple orchards. Every year, growers follow a rigorous routine in the fall by cleaning the orchard floor, cutting suckers off tree trunks and clearing weeds from under the trees. Fallen leaves, grass clippings, and winter prunings are mulched and returned to the soil. By chopping the leaves into small bits, they will decompose more quickly and neither the pests nor diseases will have anywhere to live over winter. This reduces the pest populations that will be in the orchard in the next spring. The only thing that is removed are the apples.
Just by being particular about maintaining this degree of sanitation, growers have been very successful in reducing the presence of apple scab, one of the most persistent pest problems in orchards. Apple scab comes from a fungal spore that overwinters on the ground. It normally requires a fungicide (anti-fungal pesticide) to be sprayed in order to arrest its development. Those spores go on the fruit and make leathery-brown scabs that blemish the fruit. Blemished fruit is considered to be of lower quality, so its value is reduced leading to an economic loss to the grower.
Apple scab also damages the tree because it creates lesions on the leaves that spread and interfere with photosynthesis. A bad scab infection can shut down a whole tree and spread quickly throughout the orchard. So orchard sanitation is a very important part of scab control.
Other pest prevention methods include planting pest-resistant varieties and nutrient replenishing. Just like people, apple trees need specific nutrients to keep them healthy to produce quality fruit. When hundreds of bushels of apples per acre are removed annually, it means a lot of nutrients are removed from the orchard soil. Monitoring soil nutrient levels and adding nutrients, as needed to maintain tree health, is an essential component of IPM.
Apple trees need a wide range of macro nutrients (those needed in large quantity to provide energy) including nitrogen, phosphorous and potassium. Nutrients are added either directly to the soil or by spraying on the tree leaves. Many soils in the northeast have high phosphorous levels and adequate nitrogen levels. If nitrogen is needed, it is most often applied through foliar application. Potassium is the macro nutrient (those vitamins and minerals needed in small amounts for proper plant health) that needs to be replaced on a regular basis. By running soil tests and recording the number of bushels of apples that were removed, growers can calculate how much potassium must be added back to the soil. Micronutrients, such as calcium, magnesium, zinc, boron and manganese, also need to be replenished. These are all added through foliar applications.
You can see northeastern growers discuss using IPM to prevent pests in a series of three videos by the New England Apple Association.
So why should we care about pest prevention and the appropriate use of pesticides on our apples? One reason is that apples are very prevalent in the diets of our children. They’re used to make juice and sauce, as well as eaten raw. They’re good for us! Utilizing the scientifically-based best practices of IPM, northeastern apple growers are able to provide us with high quality apples at reasonable prices.
About the Author: About the Author: Marcia is with EPA’s Center of Expertise for School IPM in Dallas, Texas. She holds a PhD in Environmental Management from Montclair State University along with degrees in Biology, Environmental Design, Landscape Architecture, and Instruction and Curriculum. Marcia was formerly with the EPA Region 2 Pesticides Program and has been a professor of Earth and Environmental Studies, Geology, and Oceanography at several universities.