North American Fruit Explorers mailing list at ibiblio

[Ed Mashburn <ribes60@currants.com>]

There have been several comments written about WPBR and the restrictions on
growing Ribes.
These restrictions vary from state to state and have to be addressed
accordingly. Generally the situation of how damaging the role of Ribes also
depends on where you are. In the Pacific NW the problem is very great,
there is a lot of damage, but there is less control because a few more
Ribes makes no difference. 


Ribes are an alternate host plant - that is the spores must travel from the
Ribes plant to the pine and then the pine gets the Blister Rust and the
spores travel to more Ribes. The disease is not systemic in the Ribes; it
is only on the leaves, and they fall off in the fall. The pines are
actually infected with the disease and sometimes die. Someone mentioned
that if the pines are trimmed of all the lower limbs, they are safe. That
is almost true, not 100%.

There are some immune black currants that do not get the disease at all,
some states have allowed those to be planted, even in restricted zones.
Some one also mentioned that there are resistant pines, that is also true
and if anyone is going to try to re-seed an area they should be used, I do
not know how difficult they are to come by.

There are several strains of WPBR and some seem more potent than others.
There are some pathologists that believe that the disease is very difficult
to transmit in states that are dry and hot during the late spring and summer.

I have about 80 varieties of gooseberries and about 65 varieties of
currants in a planting of approximately  2.5 acres, in central PA. I have
WPBR every year on some of the black currants, but have not seen it on any
gooseberries or red or white currants, except those that I have inoculated
with infected material. It is my opinion that here in PA, the disease is
not found on gooseberries, red or white currants, and some black currants.
I know that Kim Hummer has found it in some of those in Oregon, on plants
of varieties that I do not find it on naturally. 

There is no simple answer to this problem, it is being observed by a number
of people in different geographical areas. WPBR resistance is one of the
main goals of the breeding project at the University of MD. 




Northumberland BerryWorks
707 Front Street
Northumberland, PA  17857
Phone:  (570) 473-9910
WWW.currants.com
Ed@currants.com

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