Blueberry Freeze Injury or Phomopsis?

Reprinted from the Michigan State University Fruit Crop Advisory Team Alert, Vol. 18, No. 4.  Adapted for use in Connecticut.
Annemiek Schilder, Michigan State University

Do you have tip dieback this spring in your blueberry plantings? In some cases, the damage may to be due to freeze injury, while in other cases the Phomopsis fungus may be to blame.  While the two symptoms are often difficult to tell apart, there are a few differences to help you diagnose the problem.  If the dieback were due to Phomopsis, the infection would have taken place the previous year or the year before that if it weren't pruned out.  The infected twig or cane tends to be dark reddish brown with a gray-bleached area at the tip or farther down the twig or cane.  Often, the border between the dead and live portions of the cane is fairly distinct.  The bleached area may range from one to several inches long and may contain tiny black pimples, which are the fruiting bodies of the fungus.  The fungus is most likely to sporulate in the bleached area.  More recent twig infections may appear dark brown to almost black.  The lesions may be enlarging down the twig from the tip or up and down the twig from an infected lateral bud, which will die before or during bud break.  Also, if you notice that the lesions keep expanding, it is most likely Phomopsis and not freeze injury.  The fungus can infect twigs and canes anywhere on the bush.  Young green canes lower in the canopy often display reddish brown lesions (cankers) that may be flattened.  Freeze injury tends to turn cane tips a light reddish brown, without a bleached area, and the border between dead and healthy tissue is more gradual.  Freeze injury may especially affect young green canes that did not harden off well last fall. Also, the damage may be widespread throughout the field and more severe in low-lying areas that are prone to frost.  Pruning out and destroying infected canes and twigs, which act as inoculum sources, can reduce Phomopsis twig blight incidence [Editorial Note:  For fungicide options to use in controlling Phomopsis twig blight see the New England Small Fruit Pest Management Guide at http://www.umass.edu/fruitadvisor/nesfpmg/index.htm].

Cane Anthracnose Found in Some
Blueberry Fields
Reprinted from the Michigan State University Fruit Crop Advisory Team Alert, Vol. 20, No. 3.
Annemiek Schilder, Michigan State University

This spring, it is not just Phomopsis that is infecting blueberries.  One might also see unusual lesions on green blueberry canes that are dark brown to black with lighter brown centers, circular or oval and fairly sharply delineated.  Lesions vary in size, from several millimeters to 3 cm in length.  In contrast, Phomopsis lesions tend to be more elongated, often girdle the entire stem and are flattened with more diffuse margins.  The lesions may also be mistaken for Fusicoccum canker, but they can occur on any area of the cane and are not necessarily centered on a leaf scar.  So far, the lesions have only been observed in a few Jersey fields, but may be present in other varieties as well.  What is most striking are the pinkish masses of Colletotrichum spores occurring in concentric circles on the surface of these lesions.  Spore masses can be seen on canes in the field now, but if you are not sure, keep the pieces on a moist paper towel in a plastic container for a day or

two.  Anthracnose lesions will produce pink spore masses, whereas Phomopsis will produce creamy white spore blobs in a random pattern.  Both can start to look like curly strings if the humidity is just right, but Phomopsis spores have more of a tendency to do so.  Anthracnose lesions are initially fairly superficial, only killing the bark, but are assumed to develop further to girdle and kill larger portions of canes. 


The occurrence of anthracnose cane lesions is rare, though it has been reported before by researchers in Japan and was observed in Ontario last year.  It may be related to the unusually rainy weather that we had during the 2004 season, which may have provided sufficient wetness to allow infection of young green canes at a time when spores were abundant, e.g. during fruit ripening and harvest season.  It is not clear when the infections actually took place.  While studies have not been done specifically to determine the best methods to control cane anthracnose, they are likely to be similar to those that would be employed for Phomopsis: pruning out diseased and dead canes, applying lime sulfur as a delayed dormant spray, and applying fungicides on a regular basis through the season.  Since the fungus is sporulating already, it would be prudent to apply protectants, such as Bravo, Captan or Ziram at this time.  Make sure to focus sprays at the base of the bush and provide good coverage.  The goal is to protect young and emerging green canes from infection.  During and after bloom, strobilurins should be effective as well.