Foliar application of macro- and micronutrients for pest-mites control in citrus crops

Panonychus citri McGregor (Citrus red mite) and Phyllocoptruta oleivora Ashmead (Citrus rust mite) are key pests of citrus crops in the Chancay valley, Peru, causing dramatical losses in yield and fruit quality. These pest-mites affect food security in the area, where the small farming prevails, as the citrus crop is the main generating income source for most of households. Small farmers fight against these pest-mites by spraying nutritional elements on leaves, as it is cheaper and less harmful than using a chemical miticide. Thus, the aim of this work was determining the influence of the foliar application of elements currently used by farmers (Calcium, Magnesium, Zinc, Copper, Iron, Manganese, and Boron) and a mix of all of them at two dosage levels on the population dynamic of these two key citrus pests on tangerine cv. Clemenules, along a whole crop season in the Chancay Valley. Panonychus citri was detected on leaves during the whole crop cycle, while Phyllocoptruta oleivora was visible during the third leaf and bloom shooting period. There were not statistical differences between dosages, but statistical differences were observed between treatments and the control, the latter registering the highest population level of both mites during the whole crop cycle. Application of Cu, Mn, Mg, and Zn did show the lowest P.citri population rates, while Fe, Mix, Cu, Mg, and Zn did show the lowest population levels of P.oleivora. The foliage analysis revealed that the nutritional content of leaves of tangerine trees under study during the crop cycle was mostly at optimal levels, according to the standards for the crop. These results support the current practice of farmers and confirm that the foliar application of microelements represents a potential pesticide alternative method for management/control of citrus mites, lowering production costs, avoiding excessive pesticide applications, and increasing yield and fruit quality.