Lowly Ring Nematode Suppressed with
Biological Control By
A beneficial bacterium and soil solarization are an effective
biological control combination against a ring nematode species wreaking havoc
on peach trees in the southeastern United States, an
Agricultural Research Service plant
The beneficial bacterium, Pseudomonas sp (BG33R), was
isolated in the early 1990s from soil that was known to suppress the ring
nematode (Mesocriconema xenoplax) in South Carolina, according to Andrew
Nyczepir of the ARS
Fruit and Tree Nut Research Laboratory in Byron, Ga. The bacterium was
isolated by Daniel Kluepfel and Jane Lawrence of
Clemson University, Nyczepirs
colleagues in this research. BG33R was first shown to inhibit M.
xenoplax reproduction under laboratory and greenhouse conditions.
Soil solarization is a special mulching method that uses a
transparent plastic covering to trap the sun's heat, according to Nyczepir.
After months of sunny weather, many soil microorganisms are suppressed. This
disinfestation method gives beneficial bacteria, such as BG33R, a competitive
edge by lowering the native population of bacteria and killing harmful pests
like the ring nematode. Soil that has been solarized also allows plants to draw
on nutrients more readily.
Introducing BG33R after solarization treatment will help reduce
the dependence on nematicides--pesticides used specifically to manage or
prevent damage caused by nematodes, according to Nyczepir. He has searched for
alternatives to chemical control of the ring nematode in the past, and has used
other biological controls such as crop rotation or ground covers to suppress
Nyczepir and Kluepfel found that combining BG33R and soil
solarization in peach orchard field plots resulted in ring nematode populations
at or below nematicide treatment thresholds for about 18 months, unlike
Nyczepir first demonstrated that this species of nematode was a
key component to peach tree short-life disease (PTSL), which causes peach tree
losses estimated at over $6 million a year in South Carolina alone. The PTSL
disease complex occurs when ring nematodes cause trees to weaken, leaving them
vulnerable to such factors as cold injury, bacterial canker or both.
ARS is the U.S. Department of
Agricultures chief scientific research agency.