Arboriculture & Urban Forestry 43(4): July 2017 Arboriculture & Urban Forestry 2017. 43(4):133–143 133 Uptake, Movement, and Persistence of Fungi- cides in Mature Coconut Palms in Florida, U.S. Monica L. Elliott and Timothy K. Broschat Abstract. Palms are arborescent monocotyledons, with a vascular system different from eudicotyledonous trees. Compared to broad- leaf trees, very little is known about the uptake, movement and persistence of systemic fungicides into the palm canopy. In this study, conducted in 2010 and 2012, four systemic fungicides were examined in coconut palms (Cocos nucifera) in Florida, U.S., using three different application methods. A bioassay method was used to detect the fungicides every four to five weeks in palm rachises located throughout the canopy. Thiophanate methyl, which can only be applied as a soil drench, was never detected. The same was true when propiconazole and thiabendazole were applied as soil drenches. Tebuconazole, applied via infusion, was also never detected, but this appeared to be due to formulation issues. Propiconazole was detected in only two of four palms in 2010, when applied via infusion. The labeled rate had increased by 2012, and when this new rate was applied via pressure injection, the fungicide was detected in all four replicate palms. Thiabendazole, when applied via infusion or pressure injection, was detected in all four replicate palms in both years. Propiconazole and thiabendazole persisted uniformly in the canopy for at least eight weeks aſter application, but amounts tapered off aſter that time. Neither fungicide was detected in any portion of the canopy aſter 28 weeks. Both fungicides were detected in leaves that emerged aſter their application. This suggests that these fungicides may be useful for controlling some canopy diseases. Key Words. Coconut Palm; Cocos nucifera; Fungicide; Infusion; Palms; Pressure Injection; Propiconazole; Systemic Fungicides; Tebu- conazole; Thiabendazole; Thiophanate Methyl. Palms are an important landscape element through- out the state of Florida, in the United States. Unfor- tunately, they are increasingly affected by known pathogens and new or previously unrecognized fungal and fastidious bacterial pathogens (Downer et al. 2009; Elliott 2009). For two groups of lethal pathogens, phytoplasmas and Phytophthora spp., preventive disease management with trunk-injected chemicals is well-documented, and informa- tion about the chemical uptake, movement, and persistence has been determined (McCoy 1974; McCoy 1976; DeFranqueville and Renard 1989; Thévenin et al. 1995; Pohe et al. 2003; Yu et al. 2015). This is not the case with the true fungal pathogens, such as the Fusarium wilt patho- gens, or the rachis and petiole blight pathogens. The phytoplasma diseases of palms in the United States and Caribbean Basin, lethal yellowing and Texas Phoenix palm decline, are preventively man- aged by injecting the trunks of susceptible palms with the antibiotic oxytetracycline HCl. The amount, method, and timing was developed in the 1970s in response to a coconut palm (Cocos nucifera) lethal- yellowing epidemic in southern Florida and the Caribbean Basin (McCoy 1974; McCoy 1976). This research determined that a trunk injection was the most effective method for uptake of the antibiotic, which was moved throughout the palm canopy (leaf tissue), but antibiotic concentrations slowly declined to levels too low to be efficacious against the phytoplasma. Thus, the injection needed to be repeated every three to four months. Persistence in leaf tissue was determined via a biological assay. Likewise, it has been determined that Phytoph- thora bud rot can be prevented by trunk injec- tion of phosphite compounds (DeFranqueville and Renard 1989; Thévenin et al. 1995; Pohe et al. 2003), but uptake, movement, and persistence of phosphite in palms had not been examined until recently. Yu et al. (2015) determined that the likely reason phosphite injections are effective against Phytophthora bud rot is because the phosphite level ©2017 International Society of Arboriculture
July 2017
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
