� Previously our model for the appearance of symptoms was based on the assumption that inoculum accumulates at a rate proportional to the number of infected nymphs present in the citrus trees. Comparisons of these simulations with data from Southern Gardens showed that this model was not accurate. We have now implemented a model where the rate at which symptoms develop is proportional to the amount of inoculum in the tree. Furthermore the inoculum in the tree decays at some rate. � We are continuing to refine this model for the appearance of symptoms and need to investigate what the carrying capacity for inoculum is. We will investigate the impact of a local carrying capacity at the flush level as well as a carrying capacity for the whole tree. This model will continue to be refined using data from Southern Gardens and through discussions with plant pathologists to understand the phloem system and its function in symptom development. � We have had discussions with statisticians on the design of field trials to answer questions regarding how many constructs can be used in the field trial while still differentiating between constructs. Based on initial simulations from the previous model, it seems that at least four constructs can be used while still differentiating between constructs. As changes are made to the model for symptom appearance, we will need to run more simulations to determine how many constructs can be used.