Fruit Production in a Southwest Florida Citrus Grove Using the Boyd Nutrient/SAR Foliar Spray

Fruit production in Mr. Boyd's Orange Hammock citrus grove in Felda has maintained its level since being confirmed with citrus greening disease known as Huanglongbing (HLB) in 2006. The trees have been receiving the Boyd foliar cocktail mix of nutrients and SARs (Systemic Acquired Resistance) since HLB was confirmed. The grove is now 95% infected with HLB. The grove consists of 'Valencia' and 'Hamlin' sweet oranges [Citrus sinensis (L.) Osb.] on Swingle citrumelo [C. sinensis x P. trifoliate (L.) Raf.] and Carrizo citrange (C. paradise Macf. x P. trifoliate) rootstocks. The mean yield of the 6 years before HLB was detected for 'Hamlin' was 569 boxes, and after finding HLB was 576 boxes per acre. Mean yield for 'Valencia' the 6 years before HLB was 460 boxes, and after HLB was 454 boxes per acre. Plots of 'Valencia' on Swingle citrumelo rootstock containing 100 trees (10 rows of 10 trees per row) each were PCR tested in 2008, 2010, and 2012. One sample plot contained mature 'Valencia' trees planted in 1992 and another plot of younger `Valencia' trees planted in 1999. All trees in both plots were visually rated in 2010 and 2012 for symptoms of HLB using a 0 to 5 scale where 0 = vigorous tree with no symptoms of HLB to 5 = severely declined tree. Leaf samples were collected from each tree and processed by real-time PCR for detection of HLB bacteria at the U.S. Sugar HLB diagnostic lab. The mature trees tested 40% positive in 2008, 92% positive in 2010, and 95% positive in 2012. The percentage of HLB positive trees in the young trees increased from 81% in 2008, to 100% in 2010 and 2012. In 2012, the disease severity of all trees was rated less severe than in previous years. Thus, the citrus management practice of combined psyllid management and foliar nutrition/SAR sprays are maintaining tree health and production in the presence of HLB.