Organic Tree Fruit Production in New York State

 

A large number of both native and introduced pest species attack apples and other tree fruits grown in commercial orchards.  Control of this pest complex is particularly challenging in N.Y., because unlike more arid production regions in the country, fruit orchards in N.Y. are commonly in close proximity to semi-wooded areas with an abundance of naturalized and wild host species that can harbor populations of certain tree fruit pests. Traditionally, conventional fruit orchards in N.Y. have been treated heavily with pesticides to control this extensive pest complex.

 

In the past, very few growers in the northeast have attempted to produce apples and other tree fruits organically because of the practical difficulties involved in controlling pests in this region without using conventional, broad-spectrum pesticides. However, during the last 10-15 years, studies have been conducted to develop management programs that may be able to replace current strategies that rely primarily on these pesticide applications. For example, recent studies have shown that the predaceous mite, Typhlodromus pyri, which is native to apple production regions in western N.Y., can successfully control populations of the key mite pest, European red mite, in commercial apple orchards so that no applications of miticides are required for seasonal control.  Recent research in N.Y. and elsewhere has also shown that pheromones can be deployed in orchards to disrupt mating of key lepidopterous species such as oriental fruit moth, and borer species, and substantially reduce fruit damage from this complex of pests. In addition to some of these newer types of organically compatible pest control technologies, traditional control methods such as selective fruit thinning, pruning, sanitation (frequent removal of dropped fruit infested or infected with pests), removal of wild hosts near commercial plantings, and exclusion of pests with biological or physical barriers near or around trees, have also been shown to reduce populations of many types of pests in fruit plantings in this region.

 

Ideally, organic fruit production is the synthesis of an entire suite of practices intended to take advantage of natural ecosystem interactions and minimize synthetic inputs. Such a system might start with the selection of disease-resistant cultivars, to circumvent the need for the majority of normal disease sprays. This one tactic could eliminate or substantially reduce the need to manage apple scab, powdery mildew, cedar apple rust, and fire blight (Ellis et al., 1998). In lieu of resistance, a combined strategy of orchard sanitation and frequent applications of elemental sulfur and copper throughout most of the season would be the next practical alternative.

 

Sulfur is effective for controlling many fruit diseases, but it must be applied prior to infection. Sulfur is easily removed by rains. Thus, coverage must be renewed much more frequently (5-day intervals) than is required with conventional fungicides. Sulfur is not very effective for controlling rust diseases on apples.  Rust diseases in organic apple orchards can be minimized if cedars within 500 ft can be removed or if new orchards are established in areas isolated from existing or potential cedar habitat. In the Hudson Valley, sulfur is also relatively ineffective for controlling flyspeck, bitter rot, black rot and white rot on apples during July and August, but sulfur may provide adequate suppression of these diseases in more northern areas.  Liquid lime sulfur applied at 2 qt/100 gal on a 21-day interval or at 1 qt/100 gal on a 10-day interval provided good control of flyspeck in a 2006 trial in the Hudson Valley.  However, the liquid-lime sulfur sprays did not control summer fruit decays. Copper fungicides applied once or twice during late July or August should help to control both flyspeck and summer fruit decays, but this strategy needs further evaluation under New York conditions.

 

For controlling apple scab with sulfur, Burrell (1945) recommended that fruit growers maintain supplies of three sulfur-related fungicides. Wettable sulfur (which would include today’s flowable formulations) should be applied prior to rains. Dusting sulfur was recommended for application to wet foliage because it stayed in place better than liquid sprays and could be applied more quickly. Having a duster available for sulfur application was critical for maintaining coverage during long wetting periods. Liquid lime sulfur provides 60–70 hours of post-infection activity against apple scab counting from the beginning of the infection period. (Wettable sulfur has no post-infection activity!) Liquid lime sulfur is also useful to “burn out” infections after the first scab symptoms appear, but it has no activity against scab during the incubation period between 70 hours post-infection and appearance of symptoms. The number of lime-sulfur sprays should be kept to a minimum because this product will reduce yield and fruit size, and effects of multiple sprays are additive (Palmiter and Smock, 1954).

 

Copper fungicides also control many tree fruit diseases, but copper causes phytotoxicity under certain conditions. Copper is extremely phytotoxic to foliage on sweet cherries. On apples, copper applied between half-inch green and bloom usually causes fruit russetting. Copper applied between bloom and 4th cover (roughly July 4 in New York State) will cause blackening at the lenticels. Copper applied after July 4th will provide excellent control of sooty blotch and flyspeck on red apple cultivars, but July applications may still cause severe fruit discoloration of yellow cultivars. Very few copper fungicides have labels that allow application to apples after bloom.

 

Summer applications of copper fungicides have been used effectively to control bacterial leaf spot on peaches, but care is required to avoid a build-up of copper residues that can result in severe leaf injury on peaches. Repeated summer applications of copper on peaches should be avoided unless rainfall has removed the residue from the previous application. Copper has also been used to control cherry leaf spot on tart cherry.

 

Summer applications of copper fungicides have been used effectively to control bacterial leaf spot on peaches, but great care is required to avoid a build-up of copper residues that can result in severe leaf injury on peaches. Repeated summer applications of copper on peaches should be avoided unless rainfall has removed the residue from the previous application.

 

Many of the fungicides registered for use in organic tree fruit production have proven ineffective for controlling apple fungal diseases in replicated trials conducted at the Hudson Valley Lab. Serenade and OxiDate failed to control the common fungal diseases of apples in our field trials. Serenade sometimes shows suppression of fire blight and has been recommended for use in rotations with streptomycin.

 

Certain site management tactics can be incorporated that will add to the overall diversity of the orchard system, such as:

 

Companion plantings—planting flowering plants in the orchard to provide food and shelter for beneficial insects and to serve as a potential alternate cash crop.

Composting—using a composted organic mulch under the trees to provide habitat and food for insect predators, reduce fruit disease inoculum, aid in weed control, build soil structure, and provide nutrition to the trees.

 

Although we have yet to establish a complete set of procedures and guidelines to recommend to those wishing to explore the possibilities of organic tree fruit production in New York, some preliminary studies have given us a better idea of the techniques and materials that might be used in such systems. Accordingly, we are including appropriate notations to pest management options that might be considered as alternatives for organic production. In particular, certain pest management materials or products that are identified as acceptable under USDA or other commonly used organic certification guidelines, and which we have some confidence in being able to recommend at a specified level of effectiveness, are designated in this publication by preceding their name with the symbol “§”.  Because there is much variability in organic certification standards from one market to another, it will be up to the individual grower to verify that a given crop protectant or management practice is acceptable to their prospective buyer or consumer.  Look for remarks or estimates of potential levels of efficacy in the footnoted comments associated with these materials, located in the “General Pest Management Considerations” sections preceding the Pesticide Spray Tables, and also in the respective tables giving the activity spectrums for the different pesticide classes (e.g., Tables 5, 12 and 13).

 

It should be acknowledged that this “input substitution” approach is not equivalent to achieving a complete multiple-component organic system. Nevertheless, this information is being provided for those growers who may wish to explore some of the possibilities of this alternative production method, to judge their relative merits in specific orchards.

 

Burrell, A. B. 1945. Practical use of our newer knowledge of apple scab control.  Proc. N. Y. State Hort. Soc. 90: 9–16.

 

Ellis, M. A., D. C. Ferree, R. C. Funt, and L. V. Madden. 1998. Effects of an apple scab-resistant cultivar on use patterns of inorganic and organic fungicides and economics of disease control.  Plant Dis. 82: 428–433.

 

Palmiter, D. H., and R. M. Smock. 1954. Effect of fungicides on McIntosh apple yield and quality: a five-year study under Hudson Valley conditions, 1949-1953. N.Y.S. Agric. Exp. Sta. Bull. 767.  40 p.

 

Phillips, M. 1998. The Apple Grower.  Chelsea Green, White River Junction, VT.  242 pp.