Tree growth, production and huanglongbing incidence of sweet orange varieties using different nursery tree standards

Insect-proof propagation of citrus is recommended to prevent vector-transmitted pathogens such as Candidatus Liberibacter spp. and Xylella fastidiosa. Although larger nursery trees were related to a superior post-planting performance in other perennial crops, there are few studies on citrus. This fact motivated us to evaluate the tree growth, the fruit production, and the huanglongbing (HLB) incidence of four commercial sweet orange varieties ('Valencia Late', `Hamlin', `Pera' and `Folha Murcha') using two nursery tree standards (young whip and large headed trees). Eight years after planting, the tree size was similar between the evaluated treatments, especially for more vigorous varieties. However, large headed trees anticipated and increased the cumulative production by 30 % in average, which can improve the performance of reset trees in particular. Regardless the nursery tree standard and sweet orange variety, the cumulative incidence of HLB was relatively high over eight years. Therefore, a strict control of the vector should be reinforced in the field irrespectively of these factors. (AU)