By
ecoRI.org News staff
KINGSTON
— If it seems that every year you are battling a new pest or disease in your
garden, you’re not alone. According to Heather Faubert, who runs the
Plant Protection Clinic at the University of Rhode Island, that trend is
primarily due to the rapid transportation of plants around the country and the
increasing frequency of extreme weather events.
To
help local gardeners, landscapers and farmers become aware of what to be on the
lookout for this year, here is a list of Faubert’s top three plant pests and
diseases for 2013, along with a few honorable mentions:
Impatiens downy mildew. Impatiens are the top-selling annual bedding plant in the
United States, because of their colorful flowers that bloom all summer and for
their ability to fill in large spaces in the landscape. But this is not the
year to plant them — few garden centers even have them available — due to
a fungus called impatiens downy mildew.
“Early
symptoms are mottled, down-curled leaves and, later, white spores on the
underside of the leaves,” Faubert said. “Then they just die. There may be a few
leaves at the top, but the rest of the plant defoliates and dies.”
Little
can be done to protect impatiens from downy mildew, so Faubert suggests
gardeners avoid buying the plants while the nursery industry searches for a
variety that is resistant to the fungus. New Guinea impatiens, begonias and
salvias are good alternatives, she said.
 |
| Crypt Gall Wasp |
Crypt gall wasp. Red and black oak trees with sagging leaves and a thin canopy
may be struggling to combat this new invasive insect pest that appeared on Cape
Cod last year and has been found in southern Rhode Island. The crypt gall wasp
lays its eggs in the new growth of oaks and stunts their further growth.
In
the 1990s, the pests built up a large population on Long Island, but didn’t
cause many trees to die, and the wasps declined sharply after about a decade.
But landscapers on Cape Cod are concerned the infestation there is severe and
many trees will be lost.
Faubert
said affected trees can be injected with an insecticide to kill the insects,
but it is an expensive process and may not be worthwhile except on particularly
treasured trees.
Viburnum leaf beetle. This invasive European insect was found in New York in 1996
and was discovered in Warwick, Kingston, Charlestown and Glocester last week.
Faubert believes that the viburnum leaf beetle is probably in every community
in Rhode Island, where it defoliates the leaves of many species of viburnum
shrubs.
The
beetle’s eggs hatch in early May, whereupon they feed on viburnum leaves until
early June, and the adults feed on the leaves from July until the first frost.
“Unlike
most pest insects that feed on a plant either as larva or as an adult, this one
feeds on viburnum during both stages, so it could shorten the plant’s life all
the more quickly,” Faubert said.
Shrubs
shouldn’t die after one year, but two or three years of defoliation could kill
them. Faubert suggests waiting until the fall or winter when egg masses are
easily visible on branches and pruning those branches.
In
addition to these pests and diseases, Faubert encourages Rhode Islanders to be
watchful for a fungal disease that is killing mature Colorado blue spruce
trees; a scale insect whose excrement on oak trees becomes covered in black
sooty mold; boxwood blight, a fungal disease that defoliates boxwood trees; and
a Japanese fruit fly that lays its eggs in small wild and cultivated berries.
For additional information, call 401-874-2900.
