Progress report for ONE24-461
Project Information
This project seeks to:
- Monitor canopy vigor and insect-caused fruit damage of apple
cultivars during the growing season. - Assess fruit injury caused by insect pests and quality traits
of apple cultivars at harvest. - Determine apple cultivar-specific and cross-cultivar
relationships among canopy conditions, fruit quality traits, and
insect prevalence.
A large pest complex spanning the entire growing season continues to challenge apple production in the Northeast with estimated worth of over $350 million (USApple Industry Outlook, 2023). Variability in long-standing weather patterns due to climate change coupled with shifting regulations have reduced reliability of long-standing integrated pest management (IPM) practices. Plum curculio (PC), a native weevil ranging throughout Eastern North America, has become a more serious pest due to multiple generations per year and fewer labelled insecticide options (Lampasona et al., 2021). The invasive brown marmorated stink bug (BMSB) remains a destructive pest since the 2010 outbreak (Leskey and Nielsen, 2018), and mating disruption technology for codling moth (CM) and oriental fruit moth (OFM), is not widely adopted due to restrictive guidelines for deployment (Charmillot, 1990; Knight et al., 1995).
Northeastern apple growers typically have plantings of multiple cultivars in the same or nearby blocks within the same orchard to diversify and increase market opportunities. However, for these type of production systems, inherent differences among cultivars can result in difference in insect prevalence within an orchard, adding to the challenges for managing the pest complex while producing marketable apples. For example, following winter dormant pruning, differences in natural tree growing habits among apple scion cultivars contribute to variations in canopy density and microclimatic conditions, which likely influence insect phenology and their presence in apple orchards. In addition, fruit physiochemical properties associated with cultivars also play a role in insect host preference. In a preliminary study, we surveyed ‘CrimsonCrisp’, ‘Enterprise’, and ‘GoldRush’ apple on ‘Bud.9’ rootstocks within the same research block for insect damage at the USDA-ARS Appalachian Fruit Research Station (AFRS), Kearneysville, WV. Despite receiving the same insecticide program, fruit injury caused by BMSB, San Jose scale (SJS), PC, CM, and OFM, respectively, was significantly different among the three apple cultivars (Supplemental Materials). Our results reflect the difficulty in managing insect pests in orchards with multiple apple cultivars due to significant differences in how insects interact with them.
Thus far, little is known about specific pest-cultivar associations and how to best manage them in the Northeastern. Although there have been a few studies investigating the preference of insect pests for apple cultivars in the orchard agroecosystem, the trials were conducted more than a decade ago. Shifts in phenology of both insects and apple trees due to global climate change in the recent years can introduce changes in cultivar-dependent insect prevalence and thus warrant new research. Additionally, several apple cultivars included in the previous reports are no longer the most produced cultivars in the Northeast at present because of changes in market demand. It is of note that a number of cultivar-specific physiological disorders appear only in apple produced in the Mid-Atlantic area, including poor fruit set in ‘CrimsonCrisp’, cork spots in ‘WineCrisp’, and poor fruit coloring and finish issues in many new cultivars developed in other regions with distinct climate conditions. Tools to mitigate these problems are extremely limited as the internal causes in connections with localized climates and unique cultivar genetic backgrounds are not well understood.
Our proposal aims to determine cultivar-specific prevalence of insect-caused fruit injury in mixed apple orchards with at least one of the current top cultivars (e.g. Gala, Fuji, Cripps Pink) and new premium varieties. We also propose to systematically document cultivar-dependent canopy density, fruit disorders, and fruit physiochemical properties of apple trees grown in the Mid-Atlantic. This research will generate new information that is fundamental to developing innovative IPM strategies for individual apple cultivars of economic importance in the Northeast, thereby reducing grower input and increasing profitability as well as promoting ecological sustainability. Furthermore, findings from the research efforts will identify correlations of insect prevalence, canopy condition, fruit disorder, and fruit quality traits across cultivars, which will help develop optimized cultural practices, such as matching pruning techniques and/or plant growth hormone applications with apple cultivars for altering canopy microclimates, to reduce insect pest prevalence while maintaining superior fruit quality. This proposed research addresses the following aspects of sustainable agriculture: improved productivity, reduction of costs and/or increase of net farm income, and reduction of environmental and/or health risks in agriculture.
Cooperators
Research
Apple trees of two partner farmers’ commercial orchards, containing mixed cultivars, located at Smithburg (Farm 1) and Woodbine, Maryland (Farm 2) were used in this study. In both farms, we included current top cultivars, including Honeycrisp, Gala, and Fuji, as well as new premium varieties, such as WineCrisp (only at Farm 2) and MAIA-1. When individual apple cultivars reached commercial harvest standards, 20 fruit were sampled from each of the 10 exterior trees and 10 trees located in the interior of the block (20 fruit/tree; 400 fruit/cultivar) and transported to the USDA-ARS Appalachian Fruit Research Station (AFRS) in Kearneysville, WV within the same day. One exception was ‘Honeycrisp’ fruit, which were sampled from 15 interior and 5 exterior trees in Farm 1 and 20 exterior trees at Farm 2 due to the layout of the orchard blocks.
At the ARFS, half of the fruit (i.e., 10 fruit/tree) were visually and destructively assessed for damage caused by common orchard insect pests including brown marmorated stink bug (BMSB), San Jose scale (SJS), plum curculio, oriental fruit moth (OFM), and codling moth (CM). The incidence of fruit symptoms, such as bitter pit, water core, core rot, and cork spot, was also recorded during fruit cutting. The other half of collected fruit (i.e., the other 10 fruit/tree) were analyzed for the following quality-related traits. Individual fruit size was expressed in fresh weight quantified by an electronic balance. Surface red color of fruit skin was measured using a colorimeter (CR400 Chroma Meter; Konica Minolta Sensing, Osaka, Japan), and the percentage of blush coverage was estimated based on the four fruit quadrants. Skin background color, or chlorophyll content [(i.e., index of absorbance difference (IAD) of 670 and 720 nm], which is an indicator of physiological maturity, was measured by scanning the two sides of fruit with a visible-near infrared sensor (DA-Meter; T.R. Turoni, Forlì, Italy). Flesh firmness of fruit was determined by a digital penetrometer fitted with a 11-mm probe (FR-5120, Lutron, Coopersburg, PA). After dissection at the equator and applied with iodine solution, each fruit was rated for the starch pattern index (SPI), with a scale from 1 to 8 indicating 100% to 0% stained starch according to the Cornell starch-iodine index chart. For each tree, one wedge from each of the 10 fruit were pooled for juice extraction using a heavy-duty juice extractor (6001C; Waring, Stamford, CT) with a replaceable paper filter; approximately 45 mL of filtered juice was stored in a 50-mL conical tubes at -20 °C until analyses of total soluble solids concentration and titratable acidity in spring 2025.
Data of fruit quality evaluation and insect injury incidence were compared among apple cultivars grown in the same farm by first fitting to linear mixed models, in which apple cultivar was a fixed factor and tree location (exterior/interior) was a random factor; when the fixed effect (cultivar) was significant, means were separated using the Tukey’s HSD test.
The apple cultivars of interest, Honeycrisp, Gala, WineCrisp, MAIA-1, and Fuji, were harvested on August 9, August 23, October 4, October 16, and October 16, respectively; fruit samples were collected on the same day of commercial harvest. Within each farm, the fruit quality-related traits, including size (as fresh weight), skin surface and background colors, flesh firmness, and starch content, varied among the cultivars. Although the soluble solids concentration and titratable acidity in juice have not yet been quantified, it is anticipated that there will be differences in the two attributes between the cultivars. Overall, ‘Gala’ fruit were the smallest and ‘MAIA-1’ fruit were the largest in the group. The skin blush percentage of ‘Honeycrisp’ apple was significantly lower compared to other cultivars in both farms, indicating poor red coloration, which is one of the top issues of this cultivar in the mid-Atlantic region. Between the two farms, there was no consistent pattern across the apple cultivars for the index of chlorophyll in skin background color, flesh firmness, or starch pattern index, which are typically used in combination to determine the maturity of apple fruit. The index of chlorophyll in skin background color indicates the level of greenness on the fruit and is typically inversely correlated to fruit maturity. Based on this index, ‘Honeycrisp’ and ‘Gala’ were more ripen than ‘MAIA-1’ and ‘Fuji’ apple in Farm 1, but the maturity of ‘Honeycrisp’ was similar to that of ‘WineCrisp’, ‘MAIA-1’, and ‘Fuji’ in Farm 2. Despite the differences in fruit flesh firmness between cultivars, the values of all fruit obtained at the two locations were in the same recommended range for long-term storage (> 66.7 N, or 15 lb). The index of starch pattern corresponds to level of starch degradation in fruit, which occurs as fruit maturation progresses. Even though the apple cultivars exhibited differences in the starch content at Farm 1 and no difference at Farm 2, the values of starch pattern index of all fruit were greater than 7, a criterion recommended for fresh market apple.
Consumer-preferred fruit quality traits are typical priorities of apple breeding programs. It is therefore expected that fruit measurements varied among apple cultivar given the differences in the genetic background. In addition, tree growth and physiology, which can in turn affect fruit development and maturation, of the 4 or 5 apple varieties likely differed, leading to the differences in fruit physiochemical attributes observed in this report. We will investigate the association between apple tree growth and fruit traits in the following growing season, and correlate these to insect and fruit symptom incidences.
Bitter pit is a common physiological disorder for ‘Honeycrisp’ apple. Consistently, the results of our survey demonstrated that the incidence of bitter pit symptoms was the greatest in ‘Honeycrisp’ apple among the group in both farms. Although a number of research reports have suggested that ‘Honeycrisp’ and ‘Fuji’ are susceptible to water core, we observed very low to no incidence of water core symptoms, such as water-soaked or translucent tissue in fruit, of all cultivars in either Farm 1 or 2. In general, all apple cultivars in Farm 1 had relatively low incidence of cork rot and cork spot symptoms (< 10%). Nevertheless, 31% ‘WineCrisp’ and 14% ‘MAIA-1’ apple displayed symptoms of cork spot, significantly greater than the rest of the cultivars in Farm 2. Between the two farms, the patterns of incidence of cork rot and cork spot symptoms, respectively, were not consistent across the apple cultivars.
At Farm 2, cultivar had a significant effect on the incidence of injury caused by BMSB, SJS, and plum curculio. ‘Honeycrisp’ apple had the lowest incidence of both BMSB feeding injury and plum curculio oviposition scars. Honeycrisp is the earliest developing variety in this study and therefore early season fruitlets are likely too large for plum curculio to preferably oviposit in; this also indicates that the early developing phenology does not align with BMSB’s heaviest feeding periods throughout the season. In contrast, Honeycrisp was the only cultivar with SJS damage across both farms and both OFM and codling moth damage at Farm 1. These could be associated with plant biochemistry differences between cultivars affecting attraction and repellence of these insects. It is worth noting that, although there were no significant differences among cultivars at Farm 1, the pattern of damage is the same between both farms. Anecdotal evidence from growers suggests that Fuji generally has high BMSB damage, however, this was not consistent across both farms in this study. A grower survey to quantify grower issues associated with the cultivars under study will be a valuable addition to this project; these data will be collected at Winter fruit meetings in 2025.
The preliminary results of this study demonstrated differences in fruit quality-related traits, disorder symptoms, and insect-caused damages among apple cultivars of both farms. The differences in the genetic makeup of cultivars likely contribute to the variations in fruit physiochemical composition, leading to the differences in the fruit quality traits and their susceptibility to physiological disorders. Tree growth morphology will be measured and compared between the cultivars of interest the following growing season (2025) due to its possible involvement in fruit development and maturation. Cultivar-specific damage exhibited similar trends for individual insets between the two farms in 2024 and will continue to be monitored along with fruit quality traits in 2025. The results of the 2-year survey will determine insect pest prevalence associated with apple cultivars.
Education & Outreach Activities and Participation Summary
Participation Summary:
After data collection and analyses are completed, we will present synthesized results at major meetings targeting fruit growers, including Mid-Atlantic Fruit and Vegetable Convention (February 2026, Hershey, PA), Western Maryland Fruit Meeting (February 2026, Keedysville, MD), and West Virginia Ag Safety Days (February 2026, Kearneysville, WV). In addition, research findings will be disseminated at the Stakeholder Focus Group Meeting (February 2026) and Field Day (July 2026) hosted by the AFRS, Kearneysville, WV. The annual AFRS Focus Group Meeting garners 40 attendees, comprised of agricultural researchers, regulatory officials, grower and commodity stakeholders, industry representatives, and Extension personnel. The AFRS Biennial Field Day attendance has ranged 150-200 people in previous years, this captures a wider array of stakeholders, researchers, and other agricultural personnel. These events are predominantly attended by individuals throughout the Northeastern area, although the reach extends to national and international collaborators.