LAUSR

The aim of this study was to evaluate the population of Tetranychus urticae Koch (Tetranychidae – twospotted spider mite - TSSM) submitted to mineral fertilizer or crescent doses of organic compost (OC) and find its correlation with nitrogen, potassium and phenolic compounds in strawberry leaves. Production were also evaluated. Plants were cultivated in pots, in a greenhouse, for two strawberry crop cycles. Treatments were: mineral fertilization; 0.5, 1.0, 1.5, 2.0 kg of OC plant−1, and control (no fertilization). Mobile TSSM forms on young leaves were evaluated. Production were evaluated by weighting ¾ red (mature) pseudofruits. Levels of nitrogen (N), potassium (K) and total phenolic content were also measured. Plants cultivated with mineral fertilization had higher TSSM populations and foliar nutrients and lower level of phenols. In the first experiment, a higher incidence of TSSM was observed on mineral fertilized plants and plants fertilized with higher dose of OC, compared to other treatments. In the second experiment, higher TSSM incidence was observed on mineral fertilizer plants compared to 1.0, 1.5 and 2.0 kg of OC plant−1. Positive correlation between foliar nitrogen and TSSM populations and negative correlation between phenolic compounds and TSSM populations were found. Mineral fertilized plants presented higher TSSM population than OC fertilized plants despite of similar levels of N in the leaves. Pseudofruits production were higher with 1.5 OC plant−1 fertilization on both cycles.