Toward Sustainability in Northeastern Apple Production: Orchard Ecosystem Architecture, Key Pests, and Cultivar Selection
2001 was the first year of a three-year study of the influence of two major components of orchard architecture (cultivar composition and border habitats) on bio-based approaches to managing four key apple pests: plum curculio (PC), apple maggot (AMF), flyspeck disease (FS), and mites. For plum curculio and apple maggot, trapping methods were improved, susceptibility of cultivars evaluated, and influence of proximity of woods or hedgerows on injury by plum curculio or apple maggot fly evaluated. Beneficial mites were established throughout advanced-IPM blocks. A flyspeck disease predictive model was tested and refined with border surveys and tracking disease progression against distance to alternate host plants. Pesticide reductions were achieved for apple maggots and pest mites and are expected in the near future for plum curculio and flyspeck. Several new disease-resistant cultivars, such as Pristine, Enterprise, GoldRush and Florina show promise.
The primary objective was to reduce pesticide reliance in regional apple production through refinement of biologically-based management of key apple pests. The secondary objective was to enhance sustainability of northeastern apple production through evaluation of new cultivars.
Progress was made in the advancement of bio-based management of the four key pests. In particular, a baited Circle trap for PC was especially effective in capturing PCs. Sticky red spheres, when baited with a blend of five components of synthetic fruit odor were more effective for trapping-out AMF than spheres baited with a single component, except in cultivars such as Gala, Jonagold, or Fuji, which were particularly susceptible to AMF. These same cultivars were also more susceptible to PC than were Empire or MacIntosh. Cultivar composition did not have an effect on FS disease severity. Apples bordered by woods and hedgerows received more AMF and FS injury than blocks bordered by open grassy areas, while apples bordered by woods received more PC injury than apples bordered by hedgerows or open areas. An FS prediction model was refined by conducting surveys of FS on alternate hosts in border areas up to 100 m from each apple block and tracking progression of disease symptoms in marked trees at known distances from each significant border. The environmentally benign fungicide Flint performed well and can be used with confidence for summer disease and scab control. Beneficial mites were established in all advanced IPM blocks.
Pesticide reductions were obtained in all advanced IPM blocks for AMF and for mites as compared to 1st-level IPM grower-sprayed blocks. Advances in PC trap design, placement, and baiting indicate potential future pesticide reduction. Refinements in FS risk prediction pinpoint blocks or sections of orchard blocks than could receive less or no fungicide during summer months. Growers planting new blocks may achieve more pesticide reduction by placing susceptible cultivars on perimeter rows and concentrating immigrant PC and AMF there. The favorable evaluation of new scab-resistant cultivars, like Pristine, Enterprise, Goldrush, and Florina give growers another opportunity to reduce pesticidal inputs.
Impacts and Contributions/Outcomes
Background: The study was conducted in four plots of apple trees in each of 12 commercial orchards (48 plots in all). Each plot measured 30-45 meters in perimeter-row length and ran seven rows deep. In six of the 12 orchards, perimeter rows were comprised of the cultivars Gala, Jonagold or Fuji. Perimeter-row trees in the other six orchards were comprised of McIntosh or Empire cultivars. Habitat adjacent to perimeter rows consisted of woods, hedgerows or open field.
For PCs immigrating from overwintering sites in border area habitats: Wire-mesh Circle traps wrapped around trunks of perimeter-row trees and baited with a combination of benzaldehyde (a component of attractive fruit odor) and grandisoic acid (sex pheromone) captured more PCs than Circle traps baited with ethyl isovalerate plus grandisoic acid or limonene plus grandisoic acid, and more PCs than trunk-mimicking pyramid or branch-mimicking cylinder traps baited with any of these odor combinations.
Total PC captures by Circle traps baited with benzaldehyde plus grandisoic acid were significantly positively correlated with total injury. This is the first evidence anywhere that extent of PC captures by a baited trap can be useful for predicting extent of PC injury to fruit. Even so, we found no correlation between seasonal time of captures and seasonal incidence of injury.
Perimeter rows comprised of Gala, Jonagold or Fuji received more trap captures and more injury than perimeter rows comprised of McIntosh or Empire.
Orchards bordered by woods received more trap captures than orchards bordered by hedgerows or open space.
For AMF flies (AMF) immigrating from overwintering sites in border area habitats: Sticky red sphere traps baited with a five-component blend of attractive synthetic fruit odor and placed 10 meters apart on perimeter-row apple trees captured more AMF than similar traps baited with a single component of synthetic fruit odor (butyl hexanoate) placed in similar positions.
Where perimeter rows were comprised of Gala, Jonagold or Fuji, perimeter traps baited with butyl hexanoate were more effective in preventing AMF injury to perimeter and interior-row fruit than were perimeter blend-baited traps and were equally effective as grower-applied sprays. This suggests that too powerful an odor lure (five-component blend) might be counter-productive if used in association with AMF-susceptible cultivars.
Where perimeter rows were made up of McIntosh or Empire, traps baited with either blend or butyl hexanoate were equally effective in preventing AMF injury to perimeter-row and interior fruit.
Orchards bordered by woods or hedgerows received more trap captures and more injury than orchards bordered by open field.
For FS, dispersed by wind from overwintering sites in border area habitats: Disease symptoms were greater in blocks of apples that were adjacent to hedgerows and woods than in blocks bordered by open or grassy areas. The amount of overwintering FS on the alternate hosts in orchard borders in June, the proximity of these infected borders to apples, and the number and size of infected borders around a block of apples were key elements in determining damage at harvest. Cultivar composition at the perimeter of the block was not significant.
Border surveys, extending 100 meters from all edges of the blocks, determined the significance of each border as a potential FS inoculum source. Distance measurements between all significant borders and apples trees coupled with bi-monthly counts of accumulating FS injury in those same trees, identified the impact of each border on FS disease in the apples.
The environmentally benign fungicide Flint, when applied twice during the summer before and after a “conventional” Captan spray, protected the apples as well as a summer program of three or more conventional sprays.
Blocks that were adjacent to borders that had little or no FS in June, or had only grassy or distant borders, had little or no FS at harvest, regardless of the amount of summer fungicide. These blocks are candidates for further fungicide reduction. Apples that did not get summer fungicides and had moderate or high levels of FS in their borders, especially if the borders were close, had larger amounts of FS. Amount of rainfall and accumulated leaf-wetness had a positive effect on FS development both in terms of date of first appearance and severity.
For mites, which can be controlled biologically by predators: Populations of Typhlodromus pyri mite predators in 2001 were about as abundant in plots in which they were released in 2000 as in plots in which they were not released in 2000, suggesting that T. pyri spread rapidly throughout plots, although abundance in all plots was low in 2001.
Populations of Amblyseius fallacis mite predators were very low in orchard plots in 2001 and were not found on American hazel trees planted in 2000 in habitats adjacent to perimeter-row trees in an attempt to encourage buildup of this predator.
Evaluation of new cultivars
The suitability of scab-resistant apples to replace apple scab-susceptible cultivars is being evaluated in two separate blocks and observations are being made in a third at the UMass Horticultural Research Center. In the 1995 Horticulture Planting, four of the 20 cultivars are disease-resistant: Pristine, Enterprise, GoldRush, and NY 75414-1. Pristine is an extremely attractive yellow apple that ripens in early August and has commercial potential. Enterprise is a red apple and GoldRush is a yellow apple. Both ripen during the third week in October and have good commercial potential in years when temperatures average above normal. They are viable commercial apples when grown on warmer sites or in warm microclimates. NY 75414-1 is very similar to Macoun, but displays excessive pre-harvest drop, cracks severely, and becomes soft and mealy. This is not a candidate for commercial production.
In the 1999 Horticulture Planting, five of the 22 cultivars are scab-resistant: Coop 29, Coop 39, CQR 12T50, CQR 10T17, and NY 79507-72. This the first year we are taking fruit quality data, and it is too early to assess commercial potential. In a third block we evaluated Florina, a disease-resistant apple that is similar to Empire at harvest. However, Florina lost firmness and taste more rapidly after air storage. Florina appears to be a viable replacement for Empire during the harvest period, but not if a significant proportion of the crop is sold from storage after Thanksgiving.
In the 1999 Disease Planting, four of the five “scab-resistant” cultivars plus Coop25 had little or no leaf scab in June. Trees in this plot received no pesticide in 2001. CQR12T50 had 25% of its terminals infected in June. Cultivars with >60% terminal infection were NJ90, Silken, R. Macintosh, Zestar, NJ 109, Hampshire, Ambrosia, and Golden Delicious. Incidence of other disease symptoms was not significant. The same group of cultivars had the most fruit scab at harvest (ranging from Hampshire at 1.3 % infected fruit to Ambrosia at 15 %), except for Zestar, which had none. None of the scab-resistant trees had fruit scab.
Extension Educator I
Dept. of Microbiology, 203 Morrill IVN
Amherst, MA 01003
Office Phone: 4135453748
Profesor of Pomology
Dept. of Plant and Soil Science
Amherst, MA 01003
Office Phone: 4135455219
Professor of Pomology
University of Massachusetts
Dept. Of Plant and Soil Science
Amherst, MA 01003
Office Phone: 4135452963
Dept. of Entomology
Amherst, MA 01003
Office Phone: 4135451258
Dept. of Entomology
State IPM Coordinator
Agricultural Engineering Building
Amherst, MA 01003
Office Phone: 4135451051