Impact of Nutrient Applications on Asian Citrus Psyllid Populations and Tree Physiology

The Citrus Greening Disease otherwise known as Huanglongbing (HLB) has devastated the Florida citrus industry and has emerged as a threat to citrus groves in the Lower Rio Grande Valley (LRGV).   The Asian citrus psyllid (Diaphorina citri Kuwayama) is believed to be the main insect vector of citrus greening disease, which was first discovered in Florida in 1998 and was discovered in southern Texas in 2012.  In response to this threat, growers and researchers have developed management programs to control the vector in order to control the spread of the disease.  While this program has been highly successful, we must still prepare to manage trees infected with HLB. There is evidence that nutritional programs and management strategies are able to maintain tree health and keep infected citrus fields in production. The development of plant disease symptoms and tree responses to pest infestations can be linked to the nutrients that are important for plant growth. Recent field and laboratory experiments conducted at Texas A&M University - Kingsville Citrus Center have shown that applications of different nutrients applied at different rates on citrus trees have the potential to reduce psyllid populations and limit their development.  Our current research project is being conducted using applications of recommended rates and high rates of calcium and potassium silicate foliar nutrient sprays. Although not often thought of as an essential nutrient, silica (Si) is a cell structure component and is known to trigger natural defense mechanisms in plants against insects and possibly fungal disease. Calcium (Ca) is an essential macronutrient, it is important in cell wall and membrane structure as well as coordinating cellular responses to environmental stresses. Our objectives for this concurrent field and greenhouse trial is to determine the impact of multiple nutrients at variable rates on psyllid development and reproduction, as well as on tree physiology. We hypothesize that higher rates and combinations of calcium and potassium silicate will increase the leaf hardness and therefore limit the ability of psyllids to feed and reproduce.