My family and I own and operate an eight acre apple orchard in Viroqua, Wisconsin; near one of the most concentrated regions of apple production in the state. Some apple trees were already established when my parents bought the property in 1991, and we have tried to preserve many of these older trees while focusing on planting heirloom apple varieties. There are a total of 150 apple trees in production as we are in the process of clearing more space to be planted. Of these trees, approximately 40 of them are full-standard size while the rest are semi-dwarf root stock. We have not used and do not intend to use chemical sprays in the orchard. It is our goal to support a vibrant and diverse community of pollinators so we have planted many perennial plants to ensure flowers are blooming in the area for most of the growing season.
The production of hard cider is a rapidly growing industry in the North Central region of the United States. The aesthetic appearance of the fruit in hard cider apple production is negligible and so damage from fruit-feeding insect pests is less of a concern. However, foliar-feeding insects still pose a threat, killing young trees and impacting fruit size, yield and sugar content of fruit. To date, pest susceptibility and management research in apple has been done only with fresh-eating varieties. As more cider-specific varieties of apple are planted in the North Central region, knowledge regarding the susceptibility of cider apple varieties to foliar-feeding insects will improve the efficacy of insecticides by allowing growers to utilize plant host resistance to combat these insect pests. We propose a study to screen popular, cider apple varieties for foliar-feeding insect pest susceptibility, leading to the creation of a susceptibility index for each variety and specific knowledge of the timing at which each insect attacks young trees in Wisconsin. These data will provide a foundation for developing low-spray and certified organic disease management strategies for cider apple varieties based on susceptibility to insects.
- Screen popular cider-specific varieties for foliage-feeding pest susceptibility
- Document pest incidence over the growing season
- Develop a pest susceptibility index for each variety and timeline of pest incidence in apple
- Share findings with local extension educators, through conference presentations and development of a factsheet
Test Planting: For the test plot, 10 cider-specific apple varieties will be planted on semi-dwarf rootstocks with 10 single-tree replications of each variety. Trees will be planted in a randomized complete block design at a standard spacing of 15ft between semi-dwarf trees. Rows will be spaced 22ft apart to allow for vehicles between them, resulting in a 43318 sqft plot (0.99 acres). Deer-fencing will be erected around the plot allowing 22ft between row ends and the fencing. No pesticides will be applied to allow for insect colonization and damage to occur. If disease pressure for apple diseases is high, treatment will follow standard disease recommendations for the area. Irrigation will be provided as needed.
Varieties and insects chosen: The cider varieties chosen were based on popularity in the U.S. and cold-hardiness (up to zone 4 and 5) to represent cider varieties that have potential to be adapted and planted in the North Central region. Varieties chosen include: Newtown Pippin, Smokehouse, Winesap, Golden Russet, Cox Orange Pippin, Dabinett, Roxberry Russet, Harrison, Gravenstein and Summer Rambo. Foliar-feeding insect pests of concern for the North Central region include leafminer, leafhoppers and the Japanese beetle, and therefore will be specifically studied.
Data Collection/Analyses: Data will be recorded periodically as incidence (i.e. numbers on tree or tissue-feeder mines, depending on insect) and injury (recorded number or percentage of leaves affected) from various foliage-feeding insect pests (i.e. leafminers, aphids, leafhoppers, Japanese beetle) throughout growing season. Statistical analyses will be run with the two years of data on incidence and injury from each insect pest (ANOVAs with mean separation with Tukey’s test). Varieties will be ranked numerically from least to most susceptible to incidence or injury from each pest and summed to develop pest susceptibility ratings.
Foliar-feeding insect pests were counted bi-weekly on each tree following their establishment in the first week of May 2019 until late August 2019. Insect pressure was greatest in July (Figure 1). Foliar damage from insect pests was generally consistent with pest abundance, however, variation occurred based on the type of pest. For example, leaf hoppers and rosy apple aphids were observed as the most abundant pests among all apple tree cultivars (Figure 2), however, other foliar damage attributed to worms or leaf rollers was sometimes more apparent on a given tree. Apple tree cultivar was significant when average pest counts were compared across all dates and pests, indicating that Winecrisp, Whitney crab, and Franklin cider were favored by insect pests at this location (Figure 3).
Total insect pest count over time
Pest count distribution
Pest count by tree cultivar
Educational & Outreach Activities
Proposed future outreach activities:
Create factsheet with susceptibility ratings for each cider variety to various foliar insect pests. Share with state and regional extension educators and intend to distribute directly to growers at conferences.
Give talk or workshop at Wisconsin Fresh Fruit & Vegetable Growers Conference, Minnesota Apple Growers Association Annual Meeting, and Upper Midwest Regional Fruit & Vegetable Growers Association Conference.