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Fruit Fly
The Grape Root Borer
The grape root borer (GRB) Vitacea polistiformis (Harris)
is a major pest of grapes in south-eastern United States (Alm et al. 1989).
Adult female moths lay eggs on grape leaves or weeds along the trellis. Eggs
hatch into larvae, which drop to the ground and tunnel through the soil to feed
on grape roots. Larvae can remain active in the soil for up to 22 months. Damage
resulting from GRB is usually very difficult to diagnose because only roots are
damaged. Initially, muscadines grapes were thought to be resistant to GRB but
this has proved to be incorrect. (Wylie 1972). With increase production of
muscadine, table and wine grapes in the southeast, root borer has become a
common occurrence. In central and northern Florida we recorded several
vineyards infested with grape root borer during our 2001 field survey.
Currently, the best control for grape root borer is obtained with
insecticides. Currently (chlorpyrifos) Lorsban 4E is the only chemical
registered for control of GRB. One of the problems with Lorsban 4E is that the
soil around the base of the vines must be kept weed-free in order for it to be
effective. Also, Lorsban can only be applied once during the growing season and
there is a 35 days-to-harvest restriction. The identification of the GRB
pheromone (E, Z)-2, 13 octadecadien-l-ol acetate (EZ) and its improvement by the
addition of 1% (Z, Z)-3,13 octadecadienyl acetate (ZZA) (Snow et al 1987)
provided researchers with an alternative management tool for monitoring grape
root borer populations.
Previous work by Webb et al. (1992) investigated seasonal
flight activity of GRB in Florida. They found that in northern Florida,
Chattahoochee, Freeport and Alachua flight activity began in June or early July
and continued until October. In central Florida, at Leesburg, Kathleen, and
Alva, activity began in late July or early August and continued until December.
However, no attempt was made to examine trapping efficiency or to investigate
factors that may influence GRB orientation to vineyards. Trap positions and
placement are known to seriously impact insect captures (Liburd et al. 2000),
and the effectiveness of a pest management program is dependant upon knowledge
of pest problems within the field. Data obtained from effective monitoring
programs could aid growers in determining the exact time when insecticides or
other management options are needed. The ability to accurately time insecticide
sprays may also reduce the frequency of applications for informed growers.
Pheromone-based mating
disruption is a promising relatively new technique for managing lepidopteran
pests. Currently, the most efficacious method of pheromone based pest
management in fruit crops is the use of 'twist ties' or pheromone ropes, which
are polyethylene tubes containing the female sex attractant. These ropes are
usually attached to a branch in the upper part of the canopy at a rate of about
200 - 400 ropes per acre, which provides acceptable season-long crop protection
against Lepidopteran pests. Currently, our lab is trying to improve the
efficiency of deploying pheromones in the field. We are comparing different
techniques for deploying pheromones in grape vineyards in order to achieve
effective mating disruption, which will ultimately lead to a reduction in
pesticides (chlorpyrifos) Lorsban 4E for managing grape root borer.
Papers and Presentations
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