[Edited_by_A._Ciancio,_C.N.R.,_Bari,_Italy_and_K.(Bookos.org)

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P.F. ROVERSI ET AL.
3. AERIAL CONTROL
In the last decades, the increasing need to carry out direct monitoring interventions
as a consequence of diffused infestations of urticating species, showed the limit of
control means deployed only after damages was already assessed. It is important to
underline that the use of biocides to reduce large phytophagous populations cannot
solve, in the short term, public health and hygiene problems. In fact, the mass of
urticating hairs can remain for a long time in the environment rendering the areas hit
by infestations unfit for any use, even for many years.
From this overall picture of serious issues raised by lepidopteran infestations
and given that, in general, the interventions are set up in forest ecosystems in which
wide range pesticides are not allowed because of their negative environmental
fallout, new adequate strategies must be promoted. Among them, it is necessary to
combine the set up and maintaining of efficient monitoring task forces, to forecast
the beginning of new attacks, with the improvement of methods and means for the
timely deploy of biopesticides with a low environment impact.
Formulations of B. thuringiensis var. kurstaki (Btk), a naturally sporulating soil
bacteria, have been used for years in North America and Europe against lepidopteran
defoliators, in coniferous and broad-leaved woods (Martin & Bonneau, 2006; Van
Frankenhuyzen & Payne, 1993; Van Frankenhuyzen, 2000; Roversi, 2008). The
formulations are chosen on account of their effectiveness and specificity, as well as
of the rapidity with which the spores are killed by the UV radiation (Wilson &
Benoit, 1993; Leong, Cabo, & Kubinski, 1980).
In Canada and USA, most of the treatments are applied with airplanes. In Italy,
as well in other European countries like France and Germany, helicopters are
preferred for control of defoliator lepidopterans, because of their small size and the
more or less irregular borders of the areas to be treated. Further reasons are the close
association of the treated surfaces with cultivated areas or the general morphology of
their environments, which rarely present uniform landscapes over large surfaces
(Lentini & Luciano, 1995; Luciano & Lentini, 1999; Martin & Bonneau, 2006).
For aerial spreading of Btk formulations, helicopters have proved more useful
when wind speed is less than 16 kmh, to reduce drift. The best equipment is the
electrically operated rotary nozzle, mounted on bars to wet at ultra-low swath
intervals of about 30 m at each flight. GPS equipments proved also useful to record
both the flight and the complete treatment coverage.
Btk spraying experiments carried out in New Zealand against the Tussock Moth
Uraba lugens Walker, proved the reliability of an ULVA-8 spinning disc operating at
12,500 rpm and mounted above a track conveyor belt to obtain very small droplets,
with a median volume diameter of 150 μm, varying the dosis applied by changing the
belt speed and the flow rates (Mansfield et al., 2006). In Spain, Pascual, Robredo, and
Galante (1990) showed that aerial treatments using a plane distributing soluble
powders of Btk at the dose of 5 l/ha 1 (1,500 cc of commercial product with 8,500
u.i./mg 1 and 3.5 l of water), resulted in high mortality of OPM larvae, in colonies
artificially transferred to areas that were then experimentally treated.
Unlike standard protocols today available for other harmful defoliators of
mesophilous forests, i.e. Lymantria dispar (L.), noxious also to cork oak in North