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A hydraulic sprayer distributes the insecticide in a stream of liquid onto the foliage
of trees and shrubs. Foliage is usually sprayed until run-off is visible. Although limited
by the maximum reach of the spray, hydraulic sprayers can be quite effective at delivering
Btk into the crowns of trees. This method is a viable treatment option for eradication of
gypsy moth if the populations are small and isolated in known areas. In addition, ground
spraying can target only potential host vegetation and avoid treating other objects
(houses, fences, etc.) and non-host. Effectiveness decreases when tree crowns are very high or are
dense and access to the trees themselves is difficult. Other disadvantages of this method
of treatment (compared to aerial spraying) are:
- comparable efficacy to aerial spraying is
only achieved when coverage is complete provided by good access to all
host vegetation;
- it is labour intensive (therefore can be more expensive
for larger areas);
- there is greater exposure to the insecticide to both the homeowner and the applicator
(although Btk formulations pose minimal health risk);
- intrusive (requires entry onto private land; trucks and sprayers are set up in the
streets for several days);
- it must be conducted throughout the day during the daylight hours when the public is out
and about versus being conducted rapidly (less than 2 hours) in the early morning if
sprayed aerially;
- very slow (takes several weeks to cover a fraction of the area treated from the air vs.
less than two hours for aerial treatment); and,
- there may be high localized drift during daylight hours since the wind tends to increase
through the day although the spray is focused on host vegetation.
Under the recently enacted
Integrated Pest Management Act, ground spraying of Btk
formulations does not require a Pesticide Use Permit.
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