Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Phytosanitary protection of pear: four years of tests and observations also with the use of a pyrethroid alternative to D.N.O.C.

Abstract

Psylla pyri [Cacopsylla pyri] on pear in Italy has developed resistance to so many traditional insecticides that only DNOC (which left undesirable toxic residues in the environment) and amitraz were known to remain effective against this pest. The possibility of using synthetic pyrethroids as alternatives to these compounds was investigated near Modena in 1983-86, deltamethrin being substituted for DNOC each year during the first stages of plant growth. From the results, which are given in detail for each year against the various pests present, it is concluded that DNOC and deltamethrin gave basically similar effects, both in controlling the psyllid and in not killing its predators (which were still in their winter shelters at the time of application) or causing outbreaks of Panonychus ulmi (which was not as abundant as would have been expected on trees treated with a pyrethroid). Deltamethrin also gave some control of the cecidomyiid Dasineura pyri when applied just before or just after flowering. Attention is drawn to the lower concentration of insecticide (50-75 g/hl as compared with 300 g/hl for DNOC) applied during the treatments with deltamethrin, as well as the low mammalian toxicity of this compound, which thus presented less risk both to the workers applying it and to the environment. Low doses of fertilizer, and of other insecticides applied against other pests in the pear orchard, also contributed to the results, especially to the non-proliferation of initially small tetranychid populations.