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United States Department of Agriculture

Agricultural Research Service

Title: New and Emerging Pathogens of Blueberry

Author
item Polashock, James

Submitted to: New Jersey Annual Vegetable Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 8, 2007
Publication Date: January 15, 2008
Citation: Polashock, J.J. 2008. New and Emerging Pathogens of Blueberry. New Jersey Annual Vegetable Meeting Proceedings. p. 140.

Interpretive Summary: Long-lived woody crops, such as blueberry, are continually exposed to many pathogens. The severity or importance of these pathogens is dependent on a combination of factors including cultivar susceptibility, environmental conditions, cultural practices, and disease pressure. We are now seeing an increase in both the importance of some existing pathogens and the emergence of new pathogens. For example, twig blight, caused by Phomopsis vaccinii has become more prevalent and more severe. In New Jersey, this disease has historically had minimal impact. However, recent surveys suggest that extensive flower loss and the death of whole shoots are now more common. Insect transmitted diseases are also becoming more prevalent. These include bacteria – like diseases such as blueberry stunt and viruses such as blueberry scorch. This may be due to the reduction in broad spectrum insecticide use which allows the proliferation of some ‘non-target’ insects that transmit diseases. The trend toward global warming also permits higher levels of fungal inoculum to overwinter and further allows the migration of traditionally ‘southern’ diseases further north. Combating the problem requires the careful integration of all disciplines including breeding for resistance, monitoring of diseases and insects, and improved control practices.

Technical Abstract: Long-lived woody perennial crops, such as blueberry, are continually exposed to a host of pathogens. The ‘success’ or importance of these pathogens is dependent on a combination of important factors including cultivar susceptibility, environmental conditions, cultural practices, and inoculum pressure. We are now seeing an increase in both the importance of some existing pathogens and the emergence of new pathogens. For example, twig blight, caused by Phomopsis vaccinii has become more prevalent and more severe. This pathogen has traditionally been a problem in the southern states. In New Jersey, this disease has historically only had minimal impact, occasionally killing some flower buds and shoot tips. Recent surveys suggest that almost complete flower loss and the death of whole shoots in some cultivars are now more common. In fact, many P. vaccinii outbreaks are probably misdiagnosed as the more severe disease stem blight, which is caused by Botryosphaeria dothidea. Insect transmitted diseases are also becoming more prevalent. These include phytoplasmas, such as blueberry stunt and viruses such as blueberry scorch. One explanation is that the reduction in broad spectrum insecticide use has subsequently allowed the proliferation of ‘non-target’ insects such as the leafhoppers that transmit stunt. Another explanation is that the trend toward less severe winters is allowing a build up of certain insects that would normally be killed by winter freezes. The trend toward global warming also permits higher levels of fungal inoculum to overwinter and further allows the migration of traditionally ‘southern’ diseases further north. Combating the problem requires the careful integration of all disciplines including breeding for resistance, monitoring of diseases and insects, and improved control practices.

Last Modified: 7/27/2014
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