Aphids and Citrus responses to excessive nitrogen fertilization

Abstract

The aim of this study was to assess the effect of an excessive nitrogen mineral fertilizer on the vegetative growth of Citrus as well as on the densities and population dynamics of the main aphid species Aphis spiraecola Patch (Hemiptera, Aphididae). Two trials were conducted on clementine trees, Citrus clementine Hort. ex Tan. in 2016 and 2017. The quantities of nitrogen delivered varied from no nitrogen (control) to the triple recommended dose of nitrogen (3ARD) in a complete randomized block design. Results showed that all vegetative growth parameters evaluated for the clementine trees responded positively to the amount of nitrogen supplied. The highest values were obtained with the highest N doses in both years. A positive response also was observed for aphids for all doses of N even the lowest, with densities increasing proportionally to N inputs. The highest dose (3ARD) increased aphid populations by 3 times compared to the control. The aphid dynamics differed between the two years, probably under the influence of other factors such as rainfall. Thus, too much nitrogen should be avoided in Citrus orchards. Aphid management cannot be separated from the management of fertilization, as this agronomic practice would maintain aphid densities at acceptable levels without the need for repeated insecticide applications.