CHARACTERIZING INDEXES OF DAMAGE TO TOMATO BY THE 2-SPOTTED SPIDER-MITE, TETRANYCHUS-URTICAE KOCH (ACARI, TETRANYCHIDAE) TO ACHIEVE BIOLOGICAL-CONTROL

Indices of damage caused by the two-spotted spider mite (Tetranychus urticae) on tomato are described to provide information for biological control using the predator mite Phytoseiulus persimilis. Degrees of a scale of 1-5 for damage to leaflet and leaf, which when integrated to the plant can distinguish fifty classes of damage (0.0-5.0), are characterized by a number of mites and by a population structure. Scores of 3 for leaflet and leaf damage reveal 99-95% adult females and eggs, marking the end of the colonization phase. The further development of foliage damage to a score of 4 corresponds to the activity of new migrating forms (27-21%) emerging from the important egg sub-population. A plant with a damage degree of 2.0 and 2.5 has 14% and 50% respectively of its ten upper leaves presenting a damage degree of 3 and supporting 6,500 and 15,500 spider mites respectively. These scores seem to be the maximum tolerable levels. Leaves damaged at score 4 appear on plants classified at a mean leaf damage index of 2.8 and supporting 23,100 spider mites.