Diagnosis Of Nutrient Imbalance In HLB Infected Citrus Trees Using Dris and Cnd Approaches.

Citrus Huanglongbing, or HLB, is a most destructive citrus disease. Nutrient imbalance caused by HLB was investigated based on field survey data using three diagnosis procedure: Sufficiency Range Approach (SRA), DRIS and center-log transferred CND (CND-clr). The local CND-clr and DRIS norms were established and nutrient indices were computed based on two field N experiments. The results of survey group showed good correlation between fruit yields and leaf N concentration, DRIS N index and CND N index, with R² as 0.9946, 0.9804, and 0.9957 respectively. DRIS N index with incorporation of dry matter (DM) was linearly correlated well with that without DM (R²=0.9779).  The validation N trial showed the same trend for relationship between yield and N concentration and N index. The CND nutrient imbalance index, or CND r², and nutrient imbalance index (NII) showed negative correlation with yields, but the indexes could not be used to predict yields. The field survey data for HLB trees will be available soon. The three diagnosis methods will be used to find out the most limiting nutrients as well as possible nutrient interactions in HLB infected citrus trees.