Toward Sustainability in Northeastern Apple Production: Orchard Ecosystem Architecture, Key Pests, and Cultivar Selection

Toward Sustainability in Northeastern Apple Production: Orchard Ecosystem Architecture, Key Pests, and Cultivar Selection

Summary

2002 was the second 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, apple maggot, mites, and flyspeck disease. 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 of disease progression against distance to alternate host plants. Pesticide reductions were achieved for apple maggots, pest mites, and flyspeck and are expected in the near future for plum curculio. Many new disease-resistant cultivars show promise.

Objectives/Performance Targets

This was the second year of a three year study of the influence of orchard architecture (specifically the nature of cultivar composition of perimeter-row apple trees and the nature of the border area habitat) on bio-based approaches to managing four key apple pests: plum curculio (PC), apple maggot flies (AMF), flyspeck (FS), and mites. 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.

Accomplishments/Milestones

Progress was made in the advancement of bio-based management of the four key pests. In particular, a new “trap tree” approach was especially effective in monitoring 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, and were equal to grower sprays in controlling AMF. Gala, Jonagold, and Fuji were more susceptible to AMF and to PC than were Empire or MacIntosh. The cultivar which ripened last, Fuji, had the most flyspeck. 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. A FS prediction model was refined by conducting surveys of several orchard factors, such as FS on alternate hosts, in border areas up to 100 m from each apple block. Disease progression was tracked 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. The new “trap tree” approach for monitoring PC as well as further advances in PC trap design, placement, and baiting indicate potential future pesticide reduction. FS risk prediction resulted in a 37% reduction in summer fungicide (18% reduction season-long) in advanced IPM blocks as compared to 1st-level blocks. Growers planting new blocks may achieve more pesticide reduction by placing susceptible cultivars on perimeter rows and concentrating immigrant PC and AMF there. Continued favorable evaluation of new scab-resistant cultivars, like Pristine, Enterprise, Goldrush, and Florina give growers another opportunity to reduce pesticidal inputs. Results from the 1999 planting, with many additional cultivars, will be available in the near future.

Impacts and Contributions/Outcomes

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. In 2002, one of the 12 orchards was hit heavily by frost and had to withdraw from the experiment for this year.

For plum curculios (PCs) immigrating from overwintering sites in border area habitats:

Sticky clear-plexiglass panel traps baited with benzaldehyde (=a component of attractive host fruit odor) plus grandisoic acid ( PC pheromone) placed in orchard border areas (designed to capture PCs immigrating by flight) captured significantly more PCs than similarly-baited and similarly-placed black pyramid traps (designed to capture PCs immigrating by crawling) or similarly-baited wire mesh Circle traps wrapped around trunks of perimeter-row apple trees (designed to intercept PCs crawling up tree trunks). None of these trap types exhibited amounts of captures that correlated significantly with either weekly or season-long amounts of fresh ovipositional injury to fruit by adults. Hence, in contrast to optimism based on 2001 findings, none appears to offer high promise or a tool for effectively monitoring the seasonal course of PC injury to apples.

However, a totally new approach that we developed in 2002 to monitoring PC showed much promise. Termed a “trap tree” approach, it involved baiting branches of one perimeter-row tree per plot with benzaldehyde plus grandisoic acid. There was a significant level of aggregation (15-fold) of PC injury on trap trees, markedly facilitating monitoring of the seasonal course of PC injury to apples. Thus, monitoring apples on odor-baited trap trees for fresh ovipositional injury represents a new approach for determining need and timing of insecticide applications against PC.

As in 2001, 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 or hedgerow received more trap captures than orchards bordered by open field.

For apple maggot 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 (=blend) at full strength and placed 10 m apart on perimeter-row apple trees captured significantly more AMF than similar traps baited with a single component of reduced-strength synthetic fruit odor (=butyl hexanoate, or BH) placed in similar position, confirming our 2001 finding that blend is more attractive than BH alone.

Where perimeter rows were comprised of Gala, Jonagold or Fuji, perimeter traps baited with blend were equal to three grower-applied sprays of azinphosmethyl or phosmet in preventing AMF penetration into interior rows and were more effective in doing so than perimeter traps baited with BH.

Where perimeter rows were comprised of McIntosh or Empire, all three of these approaches performed equally well in preventing penetration of AMF. Overall, our 2002 results differ slightly for our 2001 results in that blend-baited traps performed better in 2002 than in 2001, possibly due to improved within-tree positioning in 2002. In all cases, blend-baited traps were equal to grower sprays in controlling AMF.

As in 2001, orchards bordered by woods or hedgerow received more trap captures and more injury than orchards bordered by open field.

For Mites, which can be controlled biologically by predators:

Abundance of pest mites (European red mite and two-spotted mite) were exceptionally low in all plots in 2002. Abundance of Typhlodromus pyri mite predators that were released in designated plots in each orchard in 2000 also was low, but it was greater than that of pest mites, suggesting that these predators were providing excellent overall control of pest mites.

There was no detectable difference in abundance of pest mites or T. pyri predators on perimeter-row trees vs. trees in the 4 th and 7 th interior rows, indicating a rather even distribution of pest and predator mites among rows.

Populations of Amblyseius fallacis mite predators were non-existent in plots of all but 1 orchard (the orchard with the most pest mites), indicating that this predator (unlike T. pyri) is not likely to be available for biocontrol purposes until pest mites have built to at least a detectable level.

As in 2001, no A. fallacis predators were found in 2002 on American hazel trees planted in 2000 in habitats adjacent to perimeter-row trees in an attempt to encourage buildup of this predator, calling into question the value of planting such hazel trees.

For flyspeck (FS), dispersed by wind from overwintering sites in border area habitats:

All blocks were evaluated for flyspeck risk in June. Reduced-fungicide programs were designed for low risk 3rd-level IPM blocks to compare with adjacent 1st-level IPM check blocks. A 37% reduction in summer fungicides was achieved in 3rd-level blocks as compared to 1st-level blocks (18% season-long reduction). An even greater reduction would have been seen, but for the understandable tendency of some cooperators to use below protocol levels of fungicide in the 1st-level blocks. In such a dry year, it is hard to justify spraying when you are pretty sure you don’t need to. The environmentally benign fungicide, Flint, performed as well as the “conventional” Captan spray. We may limit the number of applications of Flint in 2003 due to concerns about resistance development and costs, but we will continue to work with this promising material.

As in 2001, border surveys, extending 100 meters from all edges of blocks, determined potential FS inoculum sources. 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. In 2002, a new host-plant density measurement technique was tested, a technique for estimating the density of flyspeck on host-plants in the borders was improved, and measurements of border height and depth were improved.

Disease symptoms were very low in June on alternate host-plants in the orchard border areas and in September on apples in all but three blocks, due to continuing drought conditions. Flyspeck symptoms were greatest on apples that bordered on hedgerows and woods. There was no flyspeck on apples bordering open field. The block with the highest disease incidence (45 % infected in unsprayed trees) during the harvest survey (Sept.5-13) was a Fuji block, followed by a Gala block (2.9 %) and a McIntosh block (1.5%). The orchard factors which had the most statistically significant impact on flyspeck at harvest in this dry year were degree of slope and direction of slope. The Fuji site was at the bottom of a very steep northward-sloping block with a high hedgerow to the North and a deep hedgerow to the East. This block, which seemed darker and damper than the others, will be studied further. The Gala block was at the bottom of a moderately steep westward-sloping block with a deep, high woods to the West. The McIntosh block was on relatively flat ground with a deep hedgerow to the east and a deep, high woods to the north.

Evaluation of new cultivars:

2002 was the second year of fruit evaluation in the 1999 NE183 horticulture planting. These are young trees, and differences that we saw this year in bloom, fruit set, and fruit quality, need to be studied further before conclusions are drawn. We are already getting a sense of which will be the most precocious, high yielding, and best tasting cultivars. This information will be useful to growers in New England in making planting decisions on new apple cultivars.

In the 1999 disease planting, disease symptoms in 2002 were lower than usual for unsprayed trees for all diseases expect powdery mildew, due to the continued drought. In early July, significantly high leaf scab was seen in three cultivars: R. McIntosh, Hampshire, and Silken (11-7 % leaves infected), while NJ90, Ambrosia, and Delblush had 4 or 3 % leaves infected. Two cultivars had significantly high cedar apple rust: CQR10T17 and Silken (3%). Cultivars most infected with frog-eye leafspot were Zestar, CQR12T50, and NY 65707-19 (12-7 %). Four cultivars had more than 25 % of terminals infected with powdery mildew: CQR10T17, NJ90, Coop 29, and Coop 25. Over the several-week period of harvest, fruit scab was highest on R. McIntosh (11 %), followed by Silken, Zestar, and NJ90 (2 %). Flyspeck, sooty blotch, and summer rot symptoms were very low (3 %-0 %) with no differences among cultivars. As in 2001, “scab-resistant cultivars” were indeed scab-free.

Collaborators: