International Congress BIOLOGICAL PRODUCTS - Gruppo di ...

of the host, a relatively limited number of parasitoids is introduced on natural plants surrounding a plot. In this way the
auxiliaries can multiply without the risk of being killed by phytosanitary treatments normally carried out on the
grapevines. Once the population has reached a sufficient density level a flow of individuals begins and reaches the
culture and settles there; if there are no harmful interferences the colonisation is permanent but even if this is not so the
“reservoir” of the population on natural plants can guarantee a remarkable level of protection. The critical moments in
these cases are usually the capability of the antagonist to adapt to the new environment, in particular the overcoming of
the bad season, and its diffusion potential on a large radius starting from the introduction points. At the present moment
there are no definitive results as yet as to the success of this project.
A last example, which includes the combination of more measures, is the control of the grape berry moths Lobesia
botrana (Den & Schiff.) and Eupoecilia ambiguella (Hb.). The first solution is the progressive substitution of normal
treatments carried out with pesticides with techniques with a progressively lower impact on the environment, as the use
of growth regulators, of microbiological insecticides and lately with mating disruption. This last strategy uses, as is
known, large quantities of sexual pheromones whose aim is to “confuse” the males making them incapable of
distinguishing the traces secreted by the females, thus not allowing the coupling and as a consequence the reproduction.
This solution, optimal from the environmental point of view, has different “technical” limitations though, thus obtaining
the best results only if it is used on large and homogenous areas and in the presence of low populations. This last
constraint has led in the past different Authors to suggest to bring down the moths populations with ad hoc treatments
and this has not allowed the use of mating disruption in many areas in Italy. Together with this, and to eliminate these
limitations in part, habitat management measures are being introduced, whose aim is to improve the action of the
natural antagonists of the moths, in particular of the parasitoids. Since the majority of these species in the adult stage is
glyciphagous, it has been very important to guarantee them the presence of a suitable source of food, which is made up
of nectar plants in flower within or near the vineyard. The critical points are therefore two: on the one hand the presence
of species that produce nectar and are attractive for the parasitoids and, on the other hand, the continuous presence of
plants in flower. This can be obtained by sowing suitable species and with the alternate mowing of the rows.
These are clear examples of the holistic approach, which is typical of the most recent evolutions in cultural management
strategies. The control of a phytophagous insect is obtained by putting together different techniques both preventive and
curative, which involve different aspects of its biology and of its relations with the rest of the agroecosystem.
Furthermore, practices such as weeding and alternate mowing have a more complex meaning. They allow to maintain a
continuous presence of flowers, which are a fundamental source of food for many useful or indifferent arthropods
(figure 4), and they allow not only the increase of the number of their species but also the presence of denser and more
stable populations (Remund et al., 1989; Remund et al., 1992).
Nectar for Lepidoptera
Nectar for parasitoids
Urtica dioica X X X X
Lamium maculatum X X X X
Daucus carota X X X
Aegopodium podagraria X X X
Galium mollugo X X X X
Origanum vulgare X X
Rosa canina X X X X X
Rubus fruticosus X X X X X
Lonicera xylosteum X X
Figure 4 - Ecological meaning of the flora between the lines and in the adjoining areas of the vineyard with respect to
the antagonists of grape berry moths, their alternative hosts and other auxiliary species.
This data makes us suppose that in these environments a regulation of the harmful insects and mites at low population
levels and a stability of the whole agroecosystem is possible. Numerous species of parasitoids and predators which find
a great number of alternative hosts or preys among the insects and mites to be found on flowers and grass are
favourably hit by this presence. The pollen of anemophile species, instead, when it reaches the grapevine, is an
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Oophagous parasitoids
Larval parasitoids
Pupal parasitoids
Predatory mites
Pollen for predatory mites
Oophagous parasitoids of
leafhoppers