Clayton Myers

Effects of Orchard Host Plants (Apple and Peach) on Development of Oriental Fruit Moth (Lepidoptera: Tortricidae)

Abstract Studies were designed to examine the effects of host plants (apple, Malus domestica Borkh., and peach, Prunus persica L.) on the development of oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae). Oriental fruit moth larvae developed faster on peach than on apple, both on fruit as well as on growing terminal shoots. On fruit, these differences were shown to cause significant changes in both the rate (≈20–60 degree-days earlier emergence on peach than on apple) and patterns of adult emergence among several cultivars of peaches and apples. Slopes of female emergence plots varied by host in 2003, with emergence occurring over a longer period on peach cultivars than on apple cultivars (with one exception). Slopes of male emergence curves did not differ by cultivar in 2003. These host-driven effects could impact the efficacy of traditional pest management approaches and probably complicate efforts to predictively model G. molesta populations in mixed cultivar orchards. Such developmental effects may help to explain previously observed differences in patterns of pheromone trap captures in peach versus apple orchards. Host-associated effects should be incorporated into future models to develop more realistic predictive tools and thus improve integrated pest management efforts.

Effects of Orchard Host Plants on the Oviposition Preference of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Recently, the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), has emerged as a major problem on apples (Malus spp.) grown in the mid-Atlantic and midwestern United States, despite its historically important and frequent occurrence as a peach (Prunus spp.) pest. It is possible that host-driven biological phenomena may be contributing to changes in G. molesta population dynamics resulting in outbreaks in apple. Studies were designed to examine the effects of host plants on oviposition behavior, in an effort to clarify the host association status of eastern U.S. populations and also to gain insight into how pest modeling and management efforts may be altered to take into account various host-associated effects. G. molesta adults exhibited ovipositional preference for nonbearing peach trees over nonbearing apple trees in close-range choice tests conducted in the field, regardless of the larval host origin. A significant preference for peach shoots over apple shoots was observed on six of 12 sampling dates with a wild G. molesta population at the interface of adjacent peach and apple blocks. Numbers of eggs found on apple fruit were higher after peach fruit were harvested and apple fruit began to approach maturity (during the flight period for third and fourth brood adults). Possible implications for population modeling and integrated management of G. molesta are discussed.

Insect Growth Regulator Impact on Fecundity and Fertility of Adult Tufted Apple Bud Moth, Platynota idaeusalis Walker

The tufted apple bud moth, Platynota idaeusalis Walker, is a major pest of apples in the eastern United States. Resistance to conventional insecticide chemistries has made this pest difficult to co...

Response of tortricid moths and non-target insects to pheromone trap color in commercial apple orchards.

Pheromone traps are a widely used tool for monitoring pest activity in commercial apple orchards. Studies were conducted to evaluate delta-style traps painted with different colors (orange, red, yellow, green, blue, and white) for capture of obliquebanded leafroller, Choristoneura rosaceana (Harris) and oriental fruit moth, Grapholita molesta (Busck) as well as non-target muscoid flies and honeybees, Apis mellifera L. An additional study evaluated plastic, four-sided LepTrap traps of various colors in comparison with a standard delta trap for capture of obliquebanded leafroller, oriental fruit moth, tufted apple bud moth, Platynota idaeusalis (Walker), and codling moth, Cydia pomonella L. Capture of obliquebanded leafroller and oriental fruit moth was not significantly affected by trap color. Capture of non-target flies and honeybees tended to be higher in blue and white (both painted and unpainted) delta-style traps in New York apple orchards, although there was some variability in this response by orchard site. There were no differences in capture of four pest species in Pennsylvania between colored, plastic LepTrap traps and standard unpainted white delta-style traps. Given the observed differences in non-target capture, and the improved efficiencies of finding traps within tree canopies, we recommend using yellow, red, or orange delta traps for monitoring of obliquebanded leafroller, oriental fruit moth, and tufted apple bud moth.

Early-Season Host Plant Fruit Impacts on Reproductive Parameters of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a cosmopolitan pest of tree fruits, has been a significant pest in the United States since its introduction in the early 20th Century. Grapholita molesta historically has been a major pest of stone fruit. However, since the mid to late 1990s, outbreaks in commercial apple orchards in the eastern United States have become common place. This study examined the effects of larval host (e.g., apple vs. peach) on G. molesta reproduction, as a means to better understand the increased importance of G. molesta as an apple pest in the midAtlantic region. In laboratory investigations, G. molesta adults reared on apple fruit had approximately 2-fold higher fecundity than those reared on peach (F = 10.98; df = 3,101; P < 0.001). In two separate studies, when larvae were reared under either crowded or noncrowded feeding conditions, female adult longevity and oviposition period were significantly greater among moths reared as larvae on apple tha...

Susceptibility of Fruit from Diverse Apple and Crabapple Germplasm to Attack by Plum Curculio (Coleoptera: Curculionidae)

Abstract Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is an important apple, Malus domestica Borkh., pest that significantly hinders sustainable apple production in eastern North America. The potential for host plant resistance to plum curculio among apple germplasm has never been rigorously evaluated. Thus, studies were conducted to assess the susceptibility of a number of exotic and domestic Malus accessions housed at the USDA Plant Genetic Resources Unit (PGRU) “core” collection in Geneva, NY. Contrary to earlier published reports and promising data from a field assessment in 2005, these results suggest that there is probably little potential for genetic resistance to plum curculio among the Malus germplasm collection evaluated. More specifically, four Malus hybrid selections that have previously been released with claims of plum curculio resistance were shown to be susceptible to plum curculio attack. Because there are additional accessions housed at PGRU outside of the core collection that are currently classified as resistant, further studies are necessary to evaluate the true resistance qualities of these releases. It is also important to clarify such discrepancies in both the USDA online Germplasm Resources Information Network and in the horticultural literature. Although other Malus species exhibited some variability in fruit susceptibility, none could be classified as being truly resistant to plum curculio attack by any definition that would have relevance to commercial production and sale of apples.