Quantification of insecticide spatial distribution within individual citrus trees and efficacy through Asian citrus psyllid reductions under different application methods

Abstract

BACKGROUND Citrus greening disease (Huanglongbing, HLB) has infected >90% of Florida's oranges and thus growers are desperate to improve pest management strategies. In this field study, insecticide application efficacy was investigated with liquid chromatography mass spectrometry to determine if insecticide concentration and distribution were effective at killing the target pest Asian citrus psyllids (ACP). Sample discs attached to leaves were sprayed with imidacloprid and malathion at a field site in Florida. Application method, canopy height and depth, cardinal side of tree, and leaf side were considered to assess the spatial distribution of insecticides throughout citrus trees. Furthermore, ACP were inspected before and after insecticide applications to quantify psyllid population response. RESULTS Our findings show that although insecticide concentrations were high enough to kill ACP, the spatial distribution of insecticides throughout individual trees was highly variable and live ACP were detected after insecticide application. The top side of leaves received significantly more insecticide than the underside of leaves. Additionally, inadequate distribution to different areas of the tree canopy was observed for all application methods tested (aerial, ground speed‐sprayer, and ground side‐sprayer). Inspections of ACP populations before and after insecticide applications resulted in reductions of 85% (malathion) and 48–80% (imidacloprid). CONCLUSIONS The variability in insecticide spatial distribution due to application method allows remaining ACP to continue spreading citrus greening disease to unprotected trees. Further research is needed to improve insecticide application methods and technology for citrus trees in order to implement effective pest management strategies and fully target ACP to eliminate HLB. © 2020 Society of Chemical Industry

Dissipation Rates and Effectiveness of Malathion, Imidacloprid, And Dimethoate at Controlling Asian Citrus Psyllids under Field Conditions

“…Observed differences in reported half-lives and rate constants may be due to various factors including application method, insecticide physiochemical properties and type (contact or systemic), tree canopy size (older vs younger trees), or meteorological conditions like temperature, humidity, or rainfall. The spray application method impacts coverage, − and thus the insecticide concentration measured in leaf samples which could affect the rate constant when concentration-dependent (Table ). Greater tree canopy size and foliage can affect light exposure to leaf samples. ,, Thus, smaller trees, like our younger-aged trees sampled, are more likely to have less shade and moisture on leaves, and higher temperatures due to increased light exposure.…”

“…ACP data was obtained by a professional ACP inspector in the grove before and after foliar spray to compare insecticide treatments with ACP population reductions. , For each insecticide treatment, 30 rows of trees were sprayed with insecticide and inspected for ACP. ACP were counted in 3 trees in each row (the north border, middle, and south border) totaling n = 90 trees inspected for each treatment (Figure S5).…”

“…These application methods were used in our study simply because they are the methods currently used in the commercial grove based on tree age and the insecticide product label recommendations. We have previously shown how application method can impact insecticide distribution and concentration 40−42 and thus efficacy; 40,41 however, here we investigate the impact of application method on dissipation kinetics.…”

Management‐induced shifts in rhizosphere bacterial communities contribute to the control of pathogen causing citrus greening disease

“…Disease management currently depends on the efficient application and adequate distribution of insecticides to reduce the density of ACP. However, recent studies have shown that even advanced insecticide management programs fail to control the spread of HLB (Rehberg et al, 2021). The outlook for the global citrus industry is thus precarious, especially for Florida's citrus industry, which risks losing relevance and economic importance if crop yields continue to fall and trees keep dying.…”

Stereoscopic plant-protection system integrating UAVs and autonomous ground sprayers for orchards

“…Plant protection is important in the orchard production process to promote fruit production ( Zhao et al., 2017 ; Jiang et al., 2021 ), while the current means still relies on chemical spray ( Zhai et al., 2018 ; Rehberg et al., 2020 ; Zheng et al., 2020a ). It is ideal for the entire canopy of fruit trees to be uniformly covered by droplets.…”