Year One Summary

NASGA-funded project on anthracnose fruit rot

IowaStateUniversity (Mark Gleason, project director)

Year One Summary – December 8, 2005

The purpose of this study is to validate a sampling technique and PCR-based assay that provide rapid, sensitive, and reliable detection of Colletotrichum acutatumon symptomless strawberry leaves in a production field.

Anthracnose fruit rot poses a major threat to U.S. strawberry production. Recent advances have set the stage for developing an effective, integrated approach to anthracnose fruit rot management. First, new understanding of the behavior of C. acutatum during symptomless periods, and demonstration of its potential impact on disease risk, indicate that control measures targeting this period may suppress the pathogen before epidemics can cause economic losses. Second, including an anthracnose-resistant cultivar, Delmarvel, is likely to substantially enhance effectiveness of other anthracnose IPM tactics. Third, registration of more effective, reduced-risk fungicides provides better management tools than in the past, and several biological-control products may provide viable alternatives to chemical fungicides. Fourth, PCR-based methods now offer the first realistic way to detect C. acutatum in symptomless production fields. We will combine these new options into IPM tactics tailored to North Central Region strawberry growers, and compare the economic costs and benefits to conventional practices. A vigorous outreach effort will communicate the project’s findings to growers in the Region and nationally.

The results of the project are likely to be far-reaching. Anthracnose fruit rot is a serious problem throughout the U.S., so the results will have national application. Furthermore, because C. acutatum causes major diseases of other high-value U.S. crops, including blueberry, cranberry, pepper, apple, and citrus, and has symptomless phases in these crops, our findings have realistic potential to improve anthracnose IPM in these crops as well.

The past year has been used to establish the plots to be used in the trial. Because the cultivars used are June-bearing, they needed to be established in the first year. In May 2005, replicated field plots of cvs. Honeoye and Delmarvel were established at the ISU Horticulture Research Farm near Ames and at the Fruitland Research Station near Muscatine, which are 150 miles apart and represent contrasting microclimates (upland and river valley, respectively) and soil types (silty clay loam and sandy gravelly loam, respectively). Prior to planting, pre-emergence herbicides were applied. Also, soil samples were taken and analyzed, then fertilizer was applied to optimize soil fertility prior to planting. The plots have established well, despite some losses apparently caused by Verticillium wilt at the Ames site. Throughout the summer, runners and blooms were removed from the plants, and in November 2005 the plants were mulched with straw.

In October 2005, a Ph.D. student (Oscar Perez-Hernandez) began working on this project. He has established 200 potted strawberry plants in the greenhouse and has begun working on the PCR assay.