Departments of Plant Pathology and Entomology
North Carolina Cooperative Extension Service
North Carolina State University

FRUIT
AND
VEGETABLES

North Carolina Pest News
Volume 11, Number 7, May 31, 1996
Stephen J. Toth, Jr. and Thomas A. Melton, editors

The information and recommendations in this newsletter are applicable to North Carolina
and may not apply in other areas.

From: William O. Cline, Extension Plant Pathologist

Blueberry Disease Observations

Until this week, we have been blessed with good weather during the 1996 harvest, and fruit quality has been above average. However, 2.28 inches of rain fell at the Research Station in Castle Hayne, North Carolina on May 28, and more rain has fallen since. Rain or wind-blown rain is one of the best methods for fruit rot diseases to spread from infected berries to healthy berries in the field. Spore masses on infected berries are hit by raindrops and scattered to adjacent berries in the cluster or even to other fruit clusters on the bush. The spores germinate readily when water is present, and infection can take place within 12 hours. Also, berries that are handled wet are far more likely to become infected after harvest. In experiments, wet-sorted Bluechip berries had 8.2 percent decay after 7 days at 70 degrees F compared to 2.0 percent for berries handled dry on a clean surface. When the same wet surface was contaminated with spores, rots rose to 63.5 percent!

In addition to prompt postharvest cooling, the best way for a grower to combat fruit rots at this stage is to keep picking, even if that means machine-harvesting for processing in fields caught by rainy weather, until berries are dry and can once again be hand-harvested with a reasonable expectation of quality.

Herbicide injury was very apparent this week at some locations. Recent dry weather resulted in bush stress which produced typical symptoms in fields treated with Velpar or with Sinbar. Symptoms include leaf yellowing on margins and between veins, necrosis (burn) on leaf edges and, in severe cases, complete defoliation of the bush. I have also observed bleaching effects on the sepals (flower parts) at the flower or calyx end of berries. The damage often occurs at row ends or other places in the field where soil organic matter content is reduced. In most fields, bushes have already begun to recover from this injury.

Web page last updated on 3 June 1996 by Stephen J. Toth, Jr..