Grant Information
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|---|---|---|
| 211 - Insects, Mites, and Other Arthropods Affecting Plants | 999 - Citrus, general/other | 1170 - Epidemiology | 25% |
| 212 - Pathogens and Nematodes Affecting Plants | 999 - Citrus, general/other | 1170 - Epidemiology | 25% |
| 215 - Biological Control of Pests Affecting Plants | 999 - Citrus, general/other | 1170 - Epidemiology | 25% |
| 216 - Integrated Pest Management Systems | 999 - Citrus, general/other | 1170 - Epidemiology | 25% |
HLB has dominated the pest management efforts in Florida for a number of years because infected trees become less tolerant of major stresses due to root loss caused by systemic bacterial infection. As growers seek ways to increase tolerance in their trees, it is critical to understand the challenges in order to prioritize existing management efforts. Objective 1 aims to identify rootstocks with improved root health in the presence of HLB and to develop management practices to maintain root health in existing HLB affected trees. The goal is to prolong harvest of marketable fruit from HLB affected trees, including improving tree longevity and reducing fruit drop by identifying possible markers of disease in asymptomatic plants and testing rootstock and management methods for citrus production in groves with endemic HLB. Objective 2 addresses one of the potential strategies to maintain citrus production and profitability despite increased tree loss due to HLB, i.e., advanced citrus production systems (ACPS) wherein grove design and cultural practices are altered to produce higher density groves of smaller trees that achieve earlier, more sustained, and higher yields than conventional groves. ACPS alters soils in ways that reduces naturally occurring biological control of root damaging Diaprepes abbreviatus larvae (DRW) and increases the numbers of root weevils and the associated plant pathogenic oomycetes Phytophthora spp. It is critical to identify the factors that interfere with biological control in ACPS systems. Providing the cause(s) are chemical in nature, they may be remedied when understood.
Objective 1. Subobjective 1) Description of seasonal root loss and physiological changes in roots. To develop HLB root health management plans and to test rootstocks for HLB tolerance we need to know when root dieback is occurring and the relationship with the direction of phloem flow (carbohydrate transport and Las movement) and other stresses. It is also important to know the spatial pattern of root loss around the tree. Multiple field sites with ~20% HLB infection will be identified and seasonal and spatial sampling of root loss, carbohydrate content of the roots, and Las distribution will be performed on symptomatic, presymptomatic and presumed healthy trees. Subobjective 2)Determine specific root responses to HLB in potted plants and to identify Las induced responses compared to phloem disruption as markers for rapid screening of rootstock germplasm. Because the early root loss does not appear to be caused by phloem plugging, these marker phenotypes need to be HLB specific and, to be useful, not associated with carbohydrate starvation due to loss of phloem function. We will study the effects of Las on carbohydrate, root growth, root phytohormone status in HLB affected, girdled, and healthy plants in the greenhouse as trees are transplanted into larger volume pots to allow root growth. Subobjective 3)Identify rootstocks and develop measures to mitigate root loss in the presence of HLB.To improve the root health of citrus trees in Florida groves in the presence of endemic HLB, we will screen existing and new rootstock germplasm for improved root health compared to Swingle and Carrizo, which are currently most widely used. Objective 2. Subobjective 1)Identify changes in soil chemical properties under ACPS that affect natural enemies of DRW. Initially, we shall conduct laboratory experiments that focus on the nutrient elements and chemical properties such as pH and electrical conductivity that varied significantly in the field experiment comparing conventional and ACPS cultural practices. The experimental methods and design will vary based on the information we develop. Subobjective 2)Characterize the mechanism(s) by which soil chemistry affects natural enemies. Based on experiments such as that described above, we will establish experimental plots in three citrus groves to obtain different soil chemical properties. Two sites are on the central ridge and one is in the interior Flatwoods. Subobjective 3) Modify the chemistry of soils under ACPS in ways that mitigate harmful effects on natural biological control of DRW. We will use species specific primers TaqMan probes to determine the effects of various soil chemical properties on 5 species of EPNs endemic in Florida and many of their most common natural enemies.soil chemical properties
Target Audience
HLB researchers; nematologists, and Florida citrus growers
Changes / Problems
Nothing Reported
Training & Professional Development
Nothing Reported
Dissemination Streams
Nothing Reported
Next Reporting Steps
Nothing Reported