This project focused on field evaluations of synthetic host and pheromonal odor combinations for attractiveness to plum curculios, Conotrachelus nenuphar (Coleoptera: Curculionidae), with the aim of developing a monitoring device that could track the onset and extent of immigration into apple orchards, thereby maximizing plum curculio control while minimizing exposure and cost by helping growers to accurately time insecticide sprays. In a 2000 field test I screened six individual host plant volatiles, each in association with grandisoic acid (synthetic plum curculio aggregation pheromone), using panel and pyramid traps. Benzaldehyde was the most attractive host plant odor when in combination with grandisoic acid. Evaluations conducted in 2001 confirmed the attractiveness of this binary combination to both males and females across the entire period of immigration, and also revealed that benzaldehyde interacts in a synergistic manner with grandisoic acid. Additional field studies conducted in 2002 and 2003 showed that benzaldehyde at 40 mg/day of release in association with grandisoic acid at 1 mg/day of release is the most cost-effective bait combination for use in traps to monitor plum curculio immigration. I also investigated temporal dynamics of plum curculio immigration into an unsprayed section of an apple orchard over a five-year period using traps. My main goal was to determine relationships among the timing of immigration, temperature and phenological tree stage. Based on my data, I propose a pre- and a post-petal-fall period of immigration, each of which is influenced to a different extent by spring temperature. Thermal constants (expressed in Degree Days [DD] base 6.1°C, computed starting January 1st) for the start of immigration, 50th and 80th percentile of cumulative captures were 113, 249 and 412 DD, respectively. Some spatial aspects of plum curculio immigration were also studied in commercial apple orchards over a two-year period. By petal fall, most adults were found on perimeter-row trees in sprayed blocks having large trees (M.7 rootstock), but more adults were found inside of blocks than on perimeter-row trees if blocks had small trees (M.9 rootstock). Plum curculios were able to overwinter inside blocks, regardless of the presence or absence of weeds beneath trees.

The sooty blotch and flyspeck (SBFS) complex causes blemishes on apples in humid, temperate growing regions worldwide. In contrast to flyspeck etiology, the many species of fungi causing sooty blotch (SB) have not been well studied. The first set of objectives in this study was to use PCR to identify SB species isolated from apples and selected reservoir hosts in the northeastern United States, and to identify patterns of species distribution on hosts and among sites. Results indicated that Geastrumia polystigmatis was the predominant species on apples, whereas Peltaster species were more common on reservoir hosts. Species distribution varied among sites. Phylogenetic analysis of 54 G. polystigmatis isolates revealed little genetic variability in the ITS region. The second set of objectives involved investigating the response of G. polystigmatis to changes in nutrition, temperature, heat stress, and relative humidity, and in vitro responses of G. polystigmatis and Peltaster fructicola to fungicides commonly used in orchards. Observation of growth on half-strength potato dextrose agar, malt extract agar, and 2% water agar revealed that mycelial growth of G. polystigmatis was thicker and more melanized in the presence of readily available carbohydrates. Temperature range experiments demonstrated that the optimum temperature for growth was approximately 24ºC. The fungus was able to survive exposure to 32ºC for at least one week, 37ºC for at least 48 hours, and 42ºC for at least 8 hours. Growth was optimum at 99-100% relative humidity. Isolates of P. fructicola were very sensitive to thiophanate-methyl, mancozeb, cyprodinil, penthiopyrad, fenbuconazole, and trifloxystrobin. Isolates of G. polystigmatis were sensitive to thiophanate-methyl and cyprodinil, but significantly less sensitive to all other fungicides than P. fructicola. The addition of salicylhydroxamic acid to trifloxystrobin significantly reduced growth of P. fructicola, but not that of G. polystigmatis. This study represents the first in-depth investigation into the identity of species causing SB in the Northeast, the basic biology of G. polystigmatis, and the fungicide sensitivities of G. polystigmatis and P. fructicola.

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A two-year study was conducted to collect and identify hypovirulent isolates of the chestnut blight fungus (Cryphonectria parasitica) from American chestnut trees located in the Great Smoky Mountains National Park (GRSM). During the survey, 339 isolates were obtained, 54 of which had abnormal morphological characteristics in culture and 3 of these contained dsRNA. Analysis of vegetative compatibility divided all 339 isolates into 34 distinct groups, 16 of which only contained a single isolate. A total of 19 isolates (compared to 3 controls) containing abnormal cultural morphologies or dsRNA were randomly selected for use in a field trial containing 44 natural occurring healthy American chestnut trees in the Nantahala National Forest, North Carolina. Following artificial inoculation during spring of 2007, data on canker radial growth and stromata production were obtained monthly for six months. Results from the field trial indicated that 5 of the isolates, 3 of which contained dsRNA, were potentially hypovirulent based on appearance and canker growth rates compared to the controls. Data from the field trial and VC pairings indicated that one isolate, 236-1C, has potential for use as a biological control agent for the chestnut blight fungus in the GRSM, but is limited to select VC groups. Since numerous VC groups occur in the park, additional hypovirulent isolates must be identified which form anastomosis with the majority of the important groups before large scale control can succeed.

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