|Posted June 22, 2005: Flowers
and saplings may find tea refreshing. Compost tea, that is.
These teas are made from compost "brewed" for at least
24 hours with all-natural ingredients that boost growth of beneficial
microbes living in the compost. Compost teas may prove helpful in
protecting wholesale and retail nursery plants like rhododendrons,
azaleas, viburnums and oak saplings from what's known as ramorum
blight, also called ramorum die-back or sudden oak death. That's
according to Agricultural Research Service (ARS) plant pathologist
Robert G. Linderman at Corvallis, Ore.
The funguslike organism, Phytophthora ramorum, which causes these
diseases, has been found in at least 20 states. To prevent spread
of P. ramorum, more than one-half million otherwise-ready-to-sell
plants have had to be destroyed.
Some organic growers and home gardeners already apply compost teas
by either spraying them on foliage or drenching plant roots. And
although reputed to enhance plant growth and fend off disease, compost
teas have not yet been widely investigated by scientists. So Linderman
and co-investigators are studying compost teas as one of several
materials that might provide an effective, affordable, Earth-friendly
alternative to chemical pesticides for controlling P. ramorum.
In a preliminary experiment at the Horticultural Crops Research
Laboratory, where Linderman is based, he and colleagues treated
rhododendron leaves indoors with a helpful bacterium, Paenibacillus
polymyxa, taken from compost. The researchers then inoculated the
leaves with the ramorum organism. The scientists found that P. polymyxa
did not protect the foliage, but they plan to test it again--and
other potentially protective microbes--using slightly different
Discoveries by ARS scientists at Corvallis and their colleagues
at other ARS labs on both coasts will be of benefit not only to
the horticultural crops industry--the fastest growing sector of
American agriculture--but also to home gardeners, who have made
this pastime America's favorite hobby.