Phacidiopycnis washingtonensis and Sphaeropsis pyriputrescens are fungal pathogens that cause postharvest speck rot and Sphaeropsis rot, respectively, in apple. Under quarantine regulations established by the Chinese government, export of apple from Washington State to China was banned between 2012 and 2014 because of detection of these pathogens in apple shipments. Previous studies established that pycnidia of P. washingtonensis and S. pyriputrescens survive in twig cankers on manchurian crabapple which serves as a dominant pollinizer in the Washington State apple industry. These pycnidia serve as a primary source of inoculum for infection of apple fruit in the orchard. The objective of this research was to conduct a study at multiple locations in Washington State to determine the efficacy of implementing manchurian crabapple pruning as a method to control speck rot and Sphaeropsis rot in storage. Four commercial orchards at geographically distant locations in Washington State were selected in 2014 and three in 2015. In 2014, two treatments included preharvest pruning of manchurian crabapple and postharvest application of pyrimethanil and untreated control. In 2015, preharvest pruning alone (PO) of manchurian crabapple was included in addition to the two treatments examined in 2014. Pruning conducted in concert with postharvest fungicide treatment significantly reduced the incidence of speck rot and Sphaeropsis rot in storage during the initial experimental field season. During year 2, both the PO and pruning with postharvest fungicide application controlled fruit rot with no significant difference between the two treatments. Findings from this study will be instrumental for the control of these postharvest diseases and maintenance of international market access for fruit from the Pacific Northwest.
Parama Sikdar, Mike Willett, and Mark Mazzola
Suzette P. Galinato, R. Karina Gallardo, David M. Granatstein, and Mike Willett
Apple maggot (Rhagoletis pomonella) is an insect pest of apple (Malus domestica) that is currently limited in extent in the commercial production areas of Washington State thanks to a quarantine program. We estimate the costs to the Washington economy if this pest were to spread more widely. Apple maggot control costs are related to the pressure of codling moth (Cydia pomonella), the most prevalent insect pest in commercial apple production in Washington State. It was found that the losses for the Washington apple industry’s range from $510 million to $557 million, depending on the codling moth pressure. Our findings underscore the importance of an efficient quarantine program that minimized the risk of spreading the pest along with additional costs associated with quarantined areas.
Mike Willett, T.J. Smith, A.B. Peterson, H. Hinman, R.G. Stevens, T. Ley, P. Tvergyak, K.M. Williams, K.M. Maib, and J.W. Watson
In the mid-1980s, a statewide educational program was initiated to help improve productivity in replanted apple orchards. This effort began with a study of the background of the problem in Washington and an assessment of the problems growers faced when replanting orchards. An array of potential limiting factors were identified-most important, specific apple replant disease (SARD)-but also low soil pH, poor irrigation practices, arsenic (As) spray residues in the soil, soil compaction, nematodes, nutrient deficiencies, and selection of the appropriate orchard system. The educational program was delivered using a variety of methods to reach audience members with different learning styles and to provide various levels of technical information, focusing on ways to correct all limiting factors in replant situations. Results have been: Acceptance of soil fumigation as a management tool: increased recognition of soil physical, chemical, and moisture problems; reduced reliance on seedling rootstock, and an increase in the use of dwarfing, precocious understocks; and better apple tree growth and production in old apple orchard soils.