MS-level assistantship available in the Tree Ecophysiology Lab

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Manipulating the light environment in the field using shading and particle films

We are looking for a graduate student to contribute to the current knowledge about tree physiological responses to light intensity. This is a last-minute opportunity, so we are looking for someone who can start in August.

Our lab has been working using shading and particle films to improve tree physiological performance. We have shown that we can mitigate the effects of disease and improve tree growth by manipulating light intensity and distribution in the canopy. The new student will help us refine the efforts and develop recommendations for growers while gaining a deeper understanding of citrus tree water relations and photosynthetic performance. This project is ideal for a student interested in either sustainable agriculture, horticulture, or plant environmental physiology.

The selected candidates will be perform experiments to quantify these underlying tradeoffs between irradiance (light intensity) and temperature and the degree to which they affect growth. Experiments will include the impact of temperature and water use on photoprotective vs. photosynthetic tradeoffs. The selected candidate will have the opportunity to use unique methodologies at the UF Tree Ecophysiology Lab, including a range of methods to assess photosynthesis, growth and water relations. This project will focus on the woody subtropical genus, Citrus. The work focuses on field work and would include some laboratory work.

The work environment is highly collaborative, and demonstration of the ability to work in diverse teams will be valued in the selection process. Critical thinking, independent judgment, and interest in the subject matter are essential. Other valued skills include:

  • Quantitative analysis
  • Written communication
  • Experience with gas exchange methods
  • Knowledge of plant carbohydrate allocation processes or phloem function

The ecophysiology lab (website here) at the Citrus Research and Education Center in Lake Alfred, Florida, uses whole-plant physiological approaches to address challenges in horticultural productivity in perennial plants. The Citrus Research and Education Center offers ample opportunities for collaboration with 25 labs working in areas as varied as genetics, plant pathology, and entomology. The PI of the Tree Ecophysiology lab places a high importance on mentorship and the development of skills of and opportunities for students and post-doctoral scholars. If you are interested, please send your questions or a resume to Christopher Vincent at civince@ufl.edu.

Welcome to the Hurricane Recovery Project!

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This project from the Citrus Research and Education Center (CREC) will survey citrus groves across the state to assess Hurricane Ian’s impact and how quickly the trees recover from it. We hope the results of these surveys will help you better understand the medium-term impacts of hurricanes based on windspeeds. Other goals for the project include equipping you with knowledge to develop plantings that are more resilient against storms. We hope this information can help with recovery, both now and in the future. Overall, we hope this knowledge will be applicable and useful for growers to protect their groves from storm damage. To do this we will be surveying your groves monthly to measure over time the impact of Hurricane Ian.

A hurricane damaged tree and a tree involved in the study. 

This is the first update that will summarize the results of the surveys and share their potential application for grower practices. Results will eventually be published in Citrus Industry Magazine as well. An EDIS document for grower use will also be published in late 2023 outlining how to make plantings more resilient, recover from wind damage, and predict the severity of the damage on their groves based on the storm.
 
For questions or more information, please contact project leader Christopher Vincent at civince@ufl.edu.
 
We are excited to share our results with you over the next year. Please share this blog with anyone who also might find this information pertinent!

Kaolin Particle Growth

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In our study kaolin particle films helped manage pests, and also improved tree growth. Kaolin particle films are a type of mineral that can be sprayed on plants to create a protective layer. Asian citrus psyllids, the pest that transmits citrus greening disease (HLB), are attracted to the natural color of leaves and the particle films cover this. White and red colored particle films were used in this study. Trees with white and red dye had a greater growth rate of trunk girth than controls, regardless of infection. This study found that particle films helped reduce the number of psyllids on leaves, as well as increased tree growth under HLB pressure.

HLB is the current largest threat to the Florida citrus industry; citrus production has declined, and citrus trees are nearly all infected. HLB stunts tree growth and limits yield, especially if infection occurs when the trees are still small. We studied for three years whether kaolin particle films on newly planted trees could help manage psyllids. We also tracked tree growth response to particle films and HLB. 

HLB reduces the growth rate of trees and negatively affects fruit yield and other quality characteristics. HLB cannot be cured once trees are infected so pest control is the usual course of action when it comes to preventing infection. HLB is spread when adult psyllids carry the bacterium from infected trees to uninfected trees. Kaolin particle films are a potential alternative to insecticides as a way to manage psyllids and the reduction in tree growth caused by HLB.

Increased growth in treated trees happened in spite of HLB infection. The positive impact of particle films on growth is likely due to shading, reducing photoinhibition, and light redistribution to lower canopy layers. Kaolin treatments increased growth enough that they made up for the loss in growth from infection. This is promising because it helps relieve pest pressure, while increasing growth of HLB affected trees.

Kaolin Particle Pest Management

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Huanglongbing (HLB; “citrus greening disease”) is currently the biggest threat to the Florida citrus industry. HLB has caused declines in citrus production and has infected trees at a rate of 100%. Insecticides reduce Asian citrus psyllid, the pest that transmits HLB, but they don’t prevent more psyllids from moving into the planting, and they often kill the pest after transmission. This is why growers need non-insecticidal prevention options. One of these options is to apply kaolin particle films on trees to help manage psyllids.

Kaolin particle films cover the natural color of the plants, which is what ACP are attracted to. White kaolin was already known to reduce ACP, but this study tested whether red kaolin may also help mitigate ACP. ACP are attracted to the blue and ultraviolet light in the leaves and red was thought to further reduce this. We made the kaolin red by taking naturally white kaolin and mixing in a dye and a binding agent, resulting in a pinkish color.  

This field study tested the effect red and white kaolin particles had on ACP pressure over the course of two years. The particles were added to the leaves of young non-bearing Hamlin trees. Another set of trees were treated with foliar insecticide and one control set received no treatments.

Overall, trees with red kaolin had the lowest number of ACP. Trees with white kaolin had less than the trees with foliar insecticide. The control trees had the most ACP. Important to note, none of the kaolin treatments completely prevented ACP from infecting trees but merely slowed the infection down. The onset was slower in red trees than white. These findings indicate that kaolin particle films may be an alternative pest management to foliar insecticides when it comes to reducing ACP and slowing HLB infection.