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Reducing Asian citrus psyllid Infestation and disease incidence with reflective mulches

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Research by Drs. Phil Stansly and Scott Croxton, University of Florida
Article written by Phil Stansly, Scott Croxton, Elizabeth Grafton-Cardwell, Peggy G. Lemaux, & Lukasz Stelinski.
Revised August 3, 2017.

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What is the technique?

Reflective mulches are used by vegetable growers to repel plant-sucking insects such as aphids, whiteflies, and thrips that often colonize young crop plants and cause serious yield reductions due to direct feeding injury and disease transmission. These metalized mulches reflect UV light and are thus thought to disorient day flying insects that use the positioning of the sun as an orientation cue for navigation. Simple use of aluminum foil as a repellent for aphids was tested in vegetable crops as early as the 1950s. Since these early days of testing, much more weather resistant reflective mulches have been applied as a means of pest control in many crops, particularly vegetables, and have targeted several pests, often improving yields as a result of reduced pest densities. Such mulches are sometimes used in concert with targeted application of systemic insecticides, and can protect plants from infection by insect-transmitted viruses.

The Asian citrus psyllid (ACP) vector of the bacteria that cause citrus greening disease also known as huanglongbing (HLB), appeared to be an ideal candidate for susceptibility to management with reflective mulches. ACP is a day flying insect and primarily relies on vision to orient to their host plants for feeding and egg laying. As a crop, citrus is also a good candidate for treatment with ground cover mulches, since the crop often requires careful management of weed and irrigation for optimal growth. Therefore, researchers investigated the effects of applying ground cover reflective mulches in young citrus trees on the level of ACP infestation, HLB infection, tree growth, and weed incidence.

How does it improve HLB management?

Metalized mulches were found to reduce densities of ACP flying into treated plots over a 7-month sampling period as compared with control plots with bare ground or those that were treated with white-painted mulch covers. Furthermore, repelling ACP with the metalized mulch reduced the incidence of HLB infection by 45 % in the first year of the investigation and by 20% the following year. Furthermore, metalized mulch treatment in concert with drip irrigation approximately doubled growth of young trees as compared with those grown in bare ground with the standard microsprinkler irrigation practices used by growers. Weed growth was significantly reduced, as well as, water use for irrigation as compared with the grower standard treatments and bare ground controls. This initial proof of concept experiment consisted of 10 tree small plots of newly planted citrus seedlings replicated four times. In follow-up experiments with 100 tree plots replicated 5 times, protection of trees from HLB infection with metalized mulch was even more effective, particularly when incorporating a well-timed soil drench of a neonicotinoid insecticide. Furthermore, fruit yield and juice volume were both increased by using metalized reflective mulch treatment for ACP and HLB management as compared with bare ground controls at 143 weeks after treatments were applied. The researchers suggest that scaling up treatment acreage may further improve protection of young trees from HLB, as well as, further improve growth of citrus and fruit yield in areas where HLB is endemic.

Who is working on the Project?

Phil Stansly and Scott Croxton conceived, designed, and carried out this research. Stansly is with the University of Florida’s Institute of Food and Agricultural Sciences. He is a professor of entomology and is located at the Southwest Florida Research and Education Center in Immokalee, FL. Croxton is a former University of Florida graduate student and currently with Nichino America.

What are the challenges and opportunities?

Use of metalized reflective mulches requires an initial investment in mulch, bedding equipment, and drip irrigation, which has not been standard practice in large-scale citriculture in Florida. Also, it is not a stand alone treatment that will completely eliminate psyllid population without integration with other pest management tools. However, the integration of reflective mulch and drip irrigation with use of well-timed systemic insecticide treatment has been shown to deter ACP infestation, reduce HLB incidence and severity, and increase tree growth and early yield. Initial economic analysis of the small-plot trials suggest a profit benefit of the approaches given the significant improvement in yield as compared with planting citrus seedlings with bare ground. Current opportunities being investigated include improving the shape of citrus beds planted with mulch, bedding equipment, irrigation plans, and mulch longevity. Further economic analysis of larger scale applications is also underway.

Croxton SD, Stansly PA. 2013. Metalized polyethylene mulch to repel Asian citrus psyllid, slow the spread of huanglongbing and improve growth of new citrus plantings. Pest Management Science. 70: 318-323. http://onlinelibrary.wiley.com/doi/10.1002/ps.3566/full

Funding source: This project is funded by the Citrus Research and Development Foundation.