Wee L. Yee

Trap Designs for Monitoring Drosophila suzukii (Diptera: Drosophilidae)

ABSTRACT Drosophila suzukii (Matsumura), an invasive pest of small and stone fruits, has been recently detected in 39 states of the United States, Canada, Mexico, and Europe. This pest attacks ripening fruit, causing economic losses including increased management costs and crop rejection. Ongoing research aims to improve the efficacy of monitoring traps. Studies were conducted to evaluate howphysical trap features affect captures of D. suzukii.We evaluated five colors, two bait surface areas, and a top and side position for the fly entry point. Studies were conducted at 16 sites spanning seven states and provinces of North America and nine crop types. Apple cider vinegar was the standard bait in all trap types. In the overall analysis, yellow-colored traps caught significantly more flies than clear, white, and black traps; and red traps caught more than clear traps. Results by color may be influenced by crop type. Overall, the trap with a greater bait surface area caught slightly more D. suzukii than the trap with smaller area (90 vs. 40cm2). Overall, the two traps with a side-mesh entry, with or without a protective rain tent, caught more D. suzukii than the trap with a top-mesh entry and tent.

Host plant use by apple maggot, western cherry fruit fly, and other Rhagoletis species (Diptera: Tephritidae) in central Washington state

Abstract Host plant use by apple maggot fly, Rhagoletis pomonella (Walsh), 1867, western cherry fruit fly, Rhagoletis indifferens Curran, 1932, and other Rhagoletis species (Diptera: Tephritidae) in five cities or towns and several habitats of different commercial importance within south central Washington state was determined in 2004 to 2006. Rhagoletis pomonella larvae infested 0 to 1.6% of non-commercial apple trees, Malus domestica (Borkh.) Borkh., and 0 to 22.5% of wild black hawthorn, Crataegus douglasii Lindl. (Rosaceae), the first data showing R. pomonella has established within this part of the state. Rhagoletis indifferens infested 81.8 to 100% of non-commercial sweet and sour cherry trees (Prunus avium (L.) L. and Prunus cerasus L.) (0% in one area) and 21.7 to 94.7% of wild bitter cherry trees, Prunus emarginata (Dougl. ex Hook.) D. Dietr. (Rosaceae). Rhagoletis zephyria Snow, 1894, Rhagoletis basiola (Osten Sacken), 1877, Rhagoletis tabellaria (Fitch), 1855, Rhagoletis berberis Curran, 1932, and Rhagoletis completa Cresson, 1929 infested 0 or 15.4 to 100% of their normal host plants. In south central Washington, the host breadth of R. pomonella is narrow perhaps because of the hot and dry conditions, low fly densities, and low host abundance outside of orchards. Here, R. pomonella likely can be managed to meet the strict quarantine requirements of apple export. Rhagoletis indifferens management can be confined to sweet and sour cherry trees. Responses of various Rhagoletis species to plant cues and survival of flies in dry climates need to be determined to understand patterns of host use and population densities in Washington.

Host plant use by and new host records of apple maggot, western cherry fruit fly, and other Rhagoletis species (Diptera: Tephritidae) in western Washington state

Abstract Host plant use by apple maggot fly, Rhagoletis pomonella (Walsh), 1867, western cherry fruit fly, Rhagoletis indifferens Curran, 1932, and other Rhagoletis species (Diptera: Tephritidae) in western Washington state and northwestern Oregon was determined by rearing larvae in fruit to adults in 2004 to 2006. Rhagoletis pomonella infested apple, Malus domestica (Borkh.) Borkh., crab apple, Malus spp., Suksdorfs hawthorn, Crataegus suksdorfii (Sarg.) Kruscke, and English hawthorn, Crataegus monogyna Jacq. Also infested were apricot, Prunus armeniaca L., and cherry plum, Prunus cerasifera Ehrh., which are two new Washington host records for R. pomonella, and smooth hawthorn, Crataegus laevigata (Poiret) DC., Japanese plum, Prunus salicina Lindl., European mountain ash, Sorbus aucuparia L., western mountain ash, Sorbus scopulina Greene, parney cotoneaster, Cotoneaster lacteus W. W. Smith, and European cotoneaster, Cotoneaster integerrimus Medic., which are six new host records for R. pomonella. Rhagoletis indifferens infested bird cherry, Prunus padus L., and cherry plum, P. cerasifera, which are two new host records. Three, one, and one new host records were also determined for Rhagoletis tabellaria (Fitch), 1855, Rhagoletis zephyria Snow, 1894, and Rhagoletis completa Cresson, 1929, respectively. In the coast forest ecosystem of western Washington, the host breadth of both R. pomonella and R. indifferens are relatively broad, perhaps in part because of large fly populations. The discovery of 13 new hosts in western Washington suggests this region can yield a wealth of information on the adaptability of various Rhagoletis to diverse plants and host race formation in this genus.

Stage-specific mortality of Rhagoletis indifferens (Diptera: Tephritidae) exposed to three species of Steinernema nematodes

Abstract Mortality of larval, pupal, and adult western cherry fruit fly, Rhagoletis indifferens (Tephritidae) exposed to the steinernematid nematodes Steinernema carpocapsae, Steinernema feltiae, and Steinernema intermedium, was determined in the laboratory and field. Larvae were the most susceptible stage, with mortality in the three nematode treatments ranging from 62 to 100%. S. carpocapsae and S. feltiae were equally effective against larvae at both 50 and 100 infective juveniles (IJs)/cm2. S. intermedium was slightly less effective against larvae than the other two species. Mortalities of R. indifferens larvae at 0, 2, 4, and 6 days following their introduction into soil previously treated with S. carpocapsae and S. feltiae at 50 IJs/cm 2 were 78.6, 92.5, 95.0, and 77.5% and 87.5, 52.5, 92.5, and 70.0%, respectively, and at 100 IJs/cm 2 were 90.0, 92.0, 100.0, and 84.0% and 90.0, 50.0, 42.0, and 40.0%, respectively. There was no decline in mortality caused by S. carpocapsae as time progressed, whereas there was in one test with S. feltiae. Larval mortalities caused by the two species were the same in a 1:1:1 vermiculite:peat moss:sand soil mix and a more compact silt loam soil. In the field, S. carpocapsae and S. feltiae were equally effective against larvae. Pupae were not infected, but adult flies were infected by all three nematode species in the laboratory. S. carpocapsae was the most effective species at a concentration of 100 IJs/cm 2 and infected 11–53% of adults that emerged. The high pathogenicity of S. carpocapsae and S. feltiae against R. indifferens larvae and their persistence in soil as well as efficacy in different soil types indicate both nematodes hold promise as effective biological control agents of flies in isolated and abandoned lots or in yards of homeowners.

Assessing the Potential for Establishment of Western Cherry Fruit Fly using Ecological Niche Modeling

ABSTRACT Sweet cherries, Prunus avium (L.) L., grown in the western United States are exported to many countries around the world. Some of these countries have enforced strict quarantine rules and trade restrictions owing to concerns about the potential establishment and subsequent spread of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), a major quarantine pest of sweet cherry. We used 1) niche models (CLIMEX and MaxEnt) to map the climatic suitability, 2) North Carolina State University-Animal and Plant Health Inspection Service Plant Pest Forecasting System to examine chilling requirement, and 3) host distribution and availability to assess the potential for establishment of R. indifferens in areas of western North America where it currently does not exist and eight current or potential fresh sweet cherry markets: Colombia, India, Indonesia, Malaysia, Taiwan, Thailand, Venezuela, and Vietnam. Results from niche models conformed well to the current distribution of R. indifferens in western North America. MaxEnt and CLIMEX models had high performance and predicted climatic suitability in some of the countries (e.g., Andean range in Colombia and Venezuela, northern and northeastern India, central Taiwan, and parts of Vietnam). However, our results showed no potential for establishment of R. indifferens in Colombia, Indonesia, Malaysia, Taiwan, Thailand, Venezuela, and Vietnam when the optimal chilling requirement to break diapause (minimum temperature ≤3°C for at least 15 wk) was used as the criterion for whether establishment can occur. Furthermore, these countries have no host plant species available for R. indifferens. Our results can be used to make scientifically informed international trade decisions and negotiations by policy makers.

Mortality of different life stages of Rhagoletis indifferens (Diptera: Tephritidae) exposed to the entomopathogenic fungus Metarhizium anisopliae.

Effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin on the mortality of different life stages of the western cherry fruit fly, Rhagoletis indifferens Curran (Dipter...

Daily and Seasonal Activity Patterns of Rhagoletis indifferens (Diptera: Tephritidae) in Washington State

Abstract The diurnal and seasonal activity patterns of the western cherry fruit fly, Rhagoletis indifferens Curran, were determined on three sweet cherry trees, Prunus avium (L.), from 0700 to 1900 hours during June and July 2001 in Yakima County, WA. There were significant effects of time of day and season on numbers of flies seen on fruit relative to leaves, indicating that presence on or attraction to these substrates for feeding, mating, or oviposition, whether caused by visual or chemical cues, was greatly modified by temperature. When temperatures were 15–16°C at 0700 hours in early June, flies of both sexes were seen mostly on leaves, but when the temperature reached 20°C, more flies of both sexes moved onto fruit. Peak fly sightings occurred at 25–35°C, usually after 1000 hours. At >35°C, most flies vanished from view, and those seen were less active. Over the entire season, males were seen four times more often than females and spent more time on fruit than on leaves. Females were seen equally on and spent equal time on fruit and leaves when temperatures were 20–35°C. Mating was initiated on fruit but was completed on fruit and leaves. Overall fly sightings and daily temperatures were positively correlated early in the season when it was cooler, uncorrelated in the middle of the season, and negatively correlated in late season when it was warmest. The results show that R. indifferens presence and times spent on fruit and leaves are greatly altered by daily and seasonal changes in temperature, but they also suggest that at 20–35°C substrate-seeking behaviors of each sex do not change with time of day or season.

BEHAVIORAL EVIDENCE FOR FRUIT ODOR DISCRIMINATION AND SYMPATRIC HOST RACES OF RHAGOLETIS POMONELLA FLIES IN THE WESTERN UNITED STATES

The recent shift of Rhagoletis pomonella (Diptera: Tephritidae) from its native host downy hawthorn, Crataegus mollis, to introduced domesticated apple, Malus domestica, in the eastern United States is a model for sympatric host race formation. However, the fly is also present in the western United States, where it may have been introduced via infested apples within the last 60 years. In addition to apple, R. pomonella also infests two hawthorns in the West, one the native black hawthorn, C. douglasii, and the other the introduced English ornamental hawthorn, C. monogyna. Here, we test for behavioral evidence of host races in the western United States. through flight tunnel assays of western R. pomonella flies to host fruit volatile blends. We report that western apple, black hawthorn, and ornamental hawthorn flies showed significantly increased levels of upwind‐directed flight to their respective natal compared to nonnatal fruit volatile blends, consistent with host race status. We discuss the implications of the behavioral results for the origin(s) of western R. pomonella, including the possibility that western apple flies were not introduced, but may represent a recent shift from local hawthorn fly populations.

Effects of Cherries, Honeydew, and Bird Feces on Longevity and Fecundity of Rhagoletis indifferens (Diptera: Tephritidae)

Abstract In laboratory experiments, western cherry fruit flies, Rhagoletis indifferens Curran, were exposed to sweet cherries, aphid honeydew, and bird feces to determine fly longevity and fecundity. Longevity was not sustained in females and males exposed to intact unripe cherries or no food, whereas it was in females exposed to intact, fully-ripe cherries, and in females and males exposed to opened unripe or ripe cherries. Females exposed to intact fully-ripe cherries alone usually survived as long as females exposed to sucrose-yeast diets, but fecundity of flies exposed to cherries (79.5–110.8 eggs/female) was lower than that of flies exposed continuously to sucrose-yeast diets (277.5–326.2 eggs/female). Longevity of flies exposed to aphid honeydew was sustained and was similar to that of flies exposed to intact ripe cherries, sucrose-yeast, and sucrose diets. However, exposure to aphid honeydew or bird feces in the absence of ripe cherries did not result in high fecundity (4.6–32.2 eggs/female). Despite the inability of flies to extract nutrients from unripe cherries and the moderate fecundity of flies that were exposed to intact ripe cherries alone, R. indifferens was clearly capable of using its principal host fruit for both sustained longevity and egg production. Results suggest cherries damaged by birds throughout the season and intact fully-ripe cherries later in the season can contribute about the same nutrition as honeydew to female longevity, but that cherries contribute significantly more than either honeydew or bird feces to fecundity in nature.

Feeding substrates and behaviors of Western cherry fruit fly (Diptera: Tephritidae).

Abstract A study was conducted to determine the abundance of potential foods and the feeding substrates and behaviors of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in 2005, 2006, and 2007 in central Washington state. Aphid colonies with honeydew, a presumed food source for flies, were not seen on randomly selected branches of sweet cherry trees, Prunus avium L., but leaves with cherry juice, fruit that were damaged, and leaves with bird feces were commonly seen, especially later in the season. Grazing, a behavior in which the mouthparts rapidly move up and down and touch plant surfaces without discrete substances visible to the human eye, was seen more frequently in flies on leaves than on fruit. Grazing occurred more frequently than feeding on extrafloral nectaries (EFNs) on leaf petioles, cherry juice on leaves, and bird feces on leaves. The percentages of females and males that grazed on leaves were not different in 2 of 3 yr, but the percentage of females that grazed was higher in a third year. Percentages of female and male flies that fed on EFNs, cherry juice, and bird feces did not differ. More flies grazed the tops than bottoms of leaves. Flies also grazed on leaves of apple, pear, and grape. The results support the hypotheses that R. indifferens feeds mostly on leaves rather than fruit and that leaf surfaces may be the main feeding substrates for R. indifferens throughout the season.