The impact of organic fertilization on the incidence of thrips (Thrips tabaci Lind.) on onion was evaluated at Ituporanga Experimental Station in Santa Catarina State, Brazil, from August to December, 1998. The treatments using organic fertilization were based on the N needs determined by previous soil analysis. Using different organic sources were 75.0 Kg/ha of N (swine manure; Barriga Verde® poultry manure; compost; turkey manure; humus); 37.5 Kg/ha of N (swine manure half regular rate); two chemically fertilized controls with 30-120-60 Kg/ha of N-P2O5-K2O and double rate (60-240-120 Kg/ha of N-P2O5-K2O); and finally the unfertilized control. The incidence of thrips was similar between treatments with fertilized and no fertilized check. Treatments with mineral fertilization presented the same incidence of thrips when compared to organic fertilization. During severe infestation period, the correlation between the use of mineral nutrients and the T. tabaci incidence was positive and was described by a model involving the levels of K/Zn, B and N. The correlation of nutrient in the leaves and the infestation of thrips on onion was not linear. The organic fertilization can substitute the mineral one on onion crops, without reducing yield.
Allium cepa; Thrips tabaci; insect; nutrient; agroecology
