2013 Annual Report
1a.Objectives (from AD-416):
Trade barriers exist on the import of apples and cherries from the Pacific Northwest based on the presumed risk of temperate fruit flies entering and establishing in export market countries. A multi-faceted or systems approach taking into account potential fly distribution, fly detection, and fly identification components are addressed in this project. In this project we plan to evaluate potential fly distributions through modeling, evaluate attractants for flies, evaluate methods to discriminate closely related fly species, and to develop collaborations for modeling risk of infestations in orchards.
1b.Approach (from AD-416):
A. Collect existing data on basic biology of apple maggot in the Eastern U.S. and Mexico versus Pacific Northwest including obligate diapausing, facultative diapausing, and non-diapausing portions of the population. Collect existing data on WCFF in the Pacific Northwest. Data will include host range, distribution maps, climatic data, growth optima, upper and lower thermal limits, degree day models, diapause induction, maintenance, and completion.
B. Enter existing data on AM and WCFF biology as well as environmental data of importing countries into risk modeling programs. Determine baseline for risk, and identify research gaps.
C. Determine critical parameters (i.e. photoperiod, chilling requirement) for diapause induction and completion in apple maggot from Washington State. We will include obligate diapausing, facultative diapausing, and putative non-diapausing portions of AM populations.
D. Determine critical parameters for growth and development of apple maggot and Western cherry fruit fly under climatic conditions specific for tropical regions.
E. Identify improved attractants, such as fruit volatiles, for apple maggot fly in the Western U.S. Improved attractants will improve the accuracy of the data used for pest distribution, numbers (load factor), and help in establishing and maintaining quarantine areas. In addition, improved trapping methodologies will increase confidence in pest control measures with our trading partners.
F. Demonstrate that morphometric and molecular methods can reliably separate the apple maggot and snowberry maggot. Misidentification of a non-quarantine pest as a quarantine pest can adversely affect trade and negatively impact risk assessment models.
G. Hold a regional workshop on Western cherry fruit fly. The specific topic to be addressed is how to develop a model that can be used to predict the probability of an orchard being infested with cherry fruit fly.
The work summarized in this progress report relates to objectives number 1 and 5 in the Project Plan for 001-00D: 1. Develop new knowledge of the behavior, genetics, systematic, physiology, ecology, and biochemistry of the insect pests of apple, pear, and cherry, and their natural enemies, that will aid in the discovery, development, and application of management methods and technologies. 5. Develop systems approaches involving combinations of various methods and technologies, both for management of codling moth in suburban and agricultural settings, and to reduce the probability of insects infesting fruit that is packed and shipped domestically and internationally.
Apple maggot and western cherry fruit fly pupae were collected from field infested fruits and used in experiments to examine the impact of temperature, humidity, and day length on fly emergence. Initial studies on metabolic heat rates and respiration of these pupae using differential scanning calorimetry and carbon dioxide monitoring have begun.
A mathematical model was developed to predict apple maggot and western cherry fruit fly emergence as a function of duration of cold storage, rearing temperature, and photoperiod. Apple maggot and western cherry fruit fly cold hardiness was determined using the differential scanning calorimeter. We determined that apple maggot pupae take approximately 10 days to fully develop cold hardiness by suppressing their whole body supercooling points through the removal of gut contents, increases in lipid content, and binding free water. Western cherry fruit flies take approximately 7 days to develop cold hardiness through the same mechanisms as apple maggot. However, cherry fruit fly supercool to much lower temperatures when fully cold hardened than apple maggot.
We determined that western cherry fruit fly require more than 4000 degree-days to complete diapause when they do not receive at least 10 weeks of chilling at or below 5°C. Pupae exposed to optimal chilling temperature and duration required 1800 degree days to complete diapause. The whole body carbohydrate and lipid content of diapausing pupae of western cherry fruit fly in relation to cold storage duration, rearing temperature, humidity, and photoperiod were determined.
Field attraction studies were completed for a second year. Results suggest that an apple volatile blend was the most attractive in apple and hawthorn trees, and a black hawthorn volatile blend was least attractive.
We determined that apple maggot flies in apple trees were preferentially attracted to the apple volatile blend, whereas flies in ornamental hawthorn trees were preferentially attracted to the ornamental hawthorn volatile blend.
We determined that apple maggot flies adapted to using hawthorn as a host may be less of a threat to apples than flies adapted to apples. Analyses of wings of apple maggot, snowberry maggot, and their hybrids were completed, data analyzed, and results summarized.