SEASONAL AND CULTIVAR ASSOCIATED VARIATION IN THE OVIPOSITION PREFERENCE OF ORIENTAL FRUIT MOTH, (LEPIDOPTERA: TORTRICIDAE) ADULTS AND FEEDING BEHAVIOR OF NEONATE LARVAE IN APPLES

Authors: Myers, Clayton; HULL, LARRY - PENN STATE UNIVERSITY; KRAWCZYK, GRZEGORZ - PENN STATE UNIVERSITY

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2005
Publication Date: 4/1/2006
Citation: Myers, C.T., Hull, L.A., Krawczyk, G. 2006. Seasonal and cultivar associated variation in the oviposition preference of oriental fruit moth, (lepidoptera: tortricidae) adults and feeding behavior of neonate larvae in apples. Journal of Economic Entomology. 99(2): 349-358.

Interpretive Summary: Oriental fruit moth (OFM) has emerged as a very destructive pest problem on apples in the eastern United States since about 1998. The reasons for the sudden outbreaks are unknown, but one major hypothesis is that OFM exhibit different biology and behavior on different host plants. These studies were designed to investigate how OFM egg laying behavior differed between various cultivars of apple and also to investigate how larval feeding behavior on apple fruit varied by cultivar, in an effort to better understand how OFM may be controlled on different apple cultivars. In an orchard situation, OFM egg-laying did vary by cultivar, with 'Delicious' appearing to be a preferred cultivar in both years of a two year field study. The fruit cultivar also affected oviposition site preference on fruit (i.e., preference for laying eggs on the calyx, the stem bowl, or the side of fruit). Larval entry into fruit varied by cultivar, with 'Rome Beauty' being the most difficult for larvae to enter after hatch. Regardless of the site of initial larval placement on fruit, the vast majority of larvae entered fruit at either the stem bowl or the calyx. Such behavioral information underscores the need for growers and pest management practitioners to apply insecticides with adequate water volume, in order to treat the entire fruit surface, especially hard to reach areas that larvae prefer. This is especially important for many of the newer, reduced-risk insecticides on the market, which lack strong contact activity.

Technical Abstract: The Oriental fruit moth, Grapholita molesta (Busck) (OFM) (Lepidoptera: Tortricidae) has become a pest of tree fruits since its introduction to the United States in the early 20th century. OFM has historically been a major pest problem in peach production, and outbreaks in commercial apple orchards in the eastern United States were rare until the late 1990’s. Recent outbreaks in Mid-Atlantic apple orchards have lead researchers to investigate host associated effects on OFM biology, behavior, and population dynamics. Studies were designed to assess cultivar level effects in apples on oviposition and larval feeding behavior of OFM. In a mixed cultivar apple orchard, total OFM oviposition and oviposition site preferences varied between cultivars. These preferences also varied over time, when sampling was repeated at various times of the growing season. While most adult female OFM preferentially oviposited in the calyx and stem areas of apple fruit, noticeable numbers of eggs were also laid on the sides of fruit, contradicting some previous reports. OFM females exhibited a strong ovipositional preference for fruit that were previously damaged by OFM or CM. The vast majority of newly hatched OFM larvae were observed to spend less than 24 hours on the surface of apple fruit prior to entry, and this was true for several different apple cultivars. Neonate larvae exhibited a preference for entering fruit at either the stem or calyx ends, regardless of their initial site of placement. Our findings underscore the importance of adequate spray coverage and accurate timing of insecticide applications targeting OFM.