INTEGRAL FERTILIZATION IN ‘MARRS’ ORANGE TREES UNDER PRODUCTION WITH CITRUS TRISTEZA VIRUS (CTV) AND HUANGLONGBING (HLB) SYMPTOMS

Abstract

In Mexico, orange production is threatened by the incidence of diseases that affect production. Balanced nutrition is an alternative to keep trees productive and reduce damage by plant parasites. The objective of this study was to evaluate the effect of chemical, organic and combined fertilization both on the soil and foliage on the production of Marrs orange trees (C. sinensis/C. volkameriana) with incidence of citrus tristeza virus (CTV) and Huanglongbing (HLB) as confirmed by PCR. The study was conducted from August 2018 to December 2019 in Cazones, Veracruz, Mexico in a commercial plantation with six-year-old trees. Due to the irregular topography, the study was carried out in the lower and upper part of the field, in trees with three degrees of CTV and HLB symptoms. The experimental design used was randomized complete blocks in split plot arrangement with three replications. Variables evaluated were the incidence of CTV and HLB, flowering, number of fruits and yield. The highest incidence of CTV (47%) and HLB (64.7%) was found in the lower part of the field. Asymptomatic trees with mild symptoms of both diseases presented higher flowering and number of fruits in the initial phase. Chemical fertilization (100 N-22 P₂O₅-195 K₂O-30 MgO) and combined (50 % chemical plus 10 kg of compost) applied to the soil, plus foliar fertilization with zinc sulfate, iron, copper, manganese and borax increased flowering up to 96 flowers per m² of canopy in the upper part of the field, and up to 89 fruits per primary branch in the initial phase of growth. The yield per tree was very low (5 to 12 kg), due to an atypical drought in the region during fruiting. The incidence and severity of CTV and HLB, along with water stress, limit the production of the Marrs orange tree.