The Horticulture Program manager at CCE-Tompkins has learned that
tomato plants sold at a local Home & Garden Center were infected with
Late Blight. The information she received is below, and includes a
link to the Cornell plant pathology web site which shows photos of
characteristic symptoms on tomato plants, as well as some suggested
preventative treatments.
Sandy Repp
Cornell Cooperative Extension of Tompkins County
June 24, 2009
Late Blight Infected Tomato Transplants Found at Local Home & Garden
Center(s) in Tompkins County
From: Prof. Tom Zitter, Dept. of Plant Pathology, Cornell University,
Ithaca, NY 14853
Keith Perry, a colleague in Plant Pathology, brought home some
infected potted tomato plants from the Lowes store in Ithaca, NY
(Tompkins Co.) yesterday, June 23, 2009. Plants are severely
infected with late blight (Phytophthora infestans), with the symptoms
indicative of the more virulent genotype of the pathogen. Plants at
Lowes were provided by Bonnie Plants out of Alabama. There is a good
likelihood that other LB-infected plants could be on the plant
shelves at other local sources (Home Depot, Walmart, Kmart, etc.) or
already transplanted to home gardens.
We are in the process of contacting the stores to get the infected
plants destroyed. At this point we should assume that late blight
has had the opportunity to spread throughout the county (especially
with our favorable weather on Saturday and Sunday), and we assume
that all tomatoes in the area are now at risk. Although this
immediate threat would be to home gardeners, we do have considerable
tomatoes grown commercially in the area and to our east, whether in
the open field or in high tunnels. Plants provided by Bonnie Plants
are widely distributed throughout the US, so we can assume that Late
Blight will be a threat in most areas where these plants have been
distributed.
All tomato varieties (conventional and heirloom) are susceptible, but
some varieties, not currently available (like Mountain Magic), do
carry genetic resistance for LB. If symptoms are found on any plants
in the home garden, it would be prudent to destroy the plants
immediately. Place the entire plant in a plastic bag and dispose of
them into the garbage. If plants do not show signs of infection
after thorough examination, then there still may be time to apply
protectant sprays immediately and repeating if weather conditions
warrant (warm temperature with rain or heavy dews).
Characteristic symptoms are illustrated at:
http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/TomLeaf/Late_Tom.htm
and elsewhere on the Veg MD web site. The fungicide chlorothalonil
is used commercially and is effective when used before the disease
appears. Look for the common name chlorothalonil on home garden
products from major suppliers like Bonide, Ortho and others. At this
time we do not know if the genotype will also infect potato, but
since late blight has been reported on potato in other states to the
south of us, all potato growers (homeowners and commercial concerns)
should be on a week schedule with fungicide sprays. If you are
growing either tomato or potato organically, then your options for
control are limited. Copper sprays offer some help but need to be
applied preventatively and often. In NYS, two copper products that
are listed by OMRI and are registered in NY for organic use are Basic
Copper 53 and Nu-Cop in several formulations. Homeowners may also
choose to apply these or other copper products, but control will not
be as successful as when chlorothalonil is used regularly.
_______________________________________________
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