Notes on Current and Gooseberry
Diseases
White pine blister rust
Identification
Symptoms of this disease include yellowish spots on the upper leaf surface
and orangish blisters on the lower leaf surface. Infected plants defoliate
prematurely but effects of defoliation are not as severe as for powdery
mildew.
Period of activity
The rust fungus spends part of its life on wild and cultivated species
of gooseberry and currant, and part on white pine or five-needled pine.
In spring, small slightly raised yellow-orange spots appear on the underside
of infected currant leaves. These produce masses of yellow-orange spores
that can re-infect currant leaves throughout most of the growing season.
Later in the season, brownish hair-like structures develop on infected
currant leaves. These produce a small spore that travels up to 1.6 km
(1 mi.) and only infects white pine. The fungus overwinters on white pine
and in spring produces spores that can travel hundreds of miles and only
infect currants and gooseberries.
Management Notes
White pine blister rust is more serious on white pines than it is on
currants. Although the rust disease can defoliate currants, it does not
appear to significantly affect yield. However, this disease can kill white
pine trees. Because white pine blister rust has caused severe economic
losses in the forestry industry, legislation exists to restrict currant
production in many parts of the United States, although not in Ontario.
Do not grow black currants, even moderately resistant varieties, within
a 1.6 km (1 mi.) of white pines. Destroy wild gooseberry and currant plants
within a 1.6 km (1 mi) radius of cultivated currants or gooseberries and
nearby white pines. This may help reduce the impact of the disease in
a particular area.
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