Evaluation of Low-volume Sprayers Used in Asian Citrus Psyllid Control Applications

Abstract

<jats:p>The asian citrus psyllid [<jats:italic>Diaphorina citri</jats:italic> (Sternorrhyncha: Psyllidae)] is a detrimental pest to citrus (<jats:italic>Citrus</jats:italic> spp.) crops when it serves as a vector of the pathogen that causes greening (huanglongbing). Transmission of this disease causes mottling, chlorosis, dieback, and reductions in fruit size and quality. Citrus producers have found that many pesticides, when applied properly, are very effective at suppressing or eliminating asian citrus psyllids in groves. Due to the threat of greening, several pesticides have been granted Special Local Needs registration for use in the state of Florida if the product is sprayed with a volume median diameter of 90 μm or greater. A number of studies involving numerous citrus sprayers and a.i. were conducted to determine the droplet sizes generated by different sprayers operating under user-established settings and the adjustments required to those settings for the sprayers to meet the 90-μm requirement. In the sprayer tests, it was found that reductions in engine speed or increases in flow rate were required to increase droplet sizes to meet the product label-required droplet size. As the equipment tested here represent the most typical application equipment used in Florida for asian citrus psyllid control, these results will provide applicators, growers, and extension agents with general guidelines to ensure that spray systems are operated in a manner that complies with label restrictions.</jats:p>

Chemical control of the Asian citrus psyllid and of huanglongbing disease in citrus

“…They have a broad spectrum of activity and act by contact and/or systemic action(s). They are usually applied as a spray at high volume using conventional ground air‐blast applicators (tractor driven) or as a mist at low volume using specially designed and truck‐mounted applicators with fine‐orifice nozzles …”

“…Multiple foliar insecticide applications using conventional high‐volume air‐blast applicators increased the cost of citrus production. The search for a technology that could reduce burgeoning ACP management costs resulted in adoption of low‐volume mist applications originally developed for mosquito control, with some modifications . In Florida, abamectin, carbaryl, zeta ‐cypermethrin, diflubenzuron, dimethoate, fenpropathrin, malathion and spirotetramat have modified labels to apply them at low volumes for ACP control [Special Local Needs label 24(c)] .…”

“…The search for a technology that could reduce burgeoning ACP management costs resulted in adoption of low‐volume mist applications originally developed for mosquito control, with some modifications . In Florida, abamectin, carbaryl, zeta ‐cypermethrin, diflubenzuron, dimethoate, fenpropathrin, malathion and spirotetramat have modified labels to apply them at low volumes for ACP control [Special Local Needs label 24(c)] . As per the 24(c) label, when these products are applied at low volume, a minimum spray volume of 7570 mL acre −1 or 2 gal acre −1 and a spray droplet volume median diameter (VMD) of ≥90 µm should be maintained .…”

“…In Florida, abamectin, carbaryl, zeta ‐cypermethrin, diflubenzuron, dimethoate, fenpropathrin, malathion and spirotetramat have modified labels to apply them at low volumes for ACP control [Special Local Needs label 24(c)] . As per the 24(c) label, when these products are applied at low volume, a minimum spray volume of 7570 mL acre −1 or 2 gal acre −1 and a spray droplet volume median diameter (VMD) of ≥90 µm should be maintained . Studies conducted under Florida conditions have shown that ACP control obtained at low‐volume ground applications is as good as or better than high‐volume conventional ground applications…”

“…They are usually applied as a spray at high volume using conventional ground air-blast applicators (tractor driven) or as a mist at low volume using specially designed and truck-mounted applicators with fine-orifice nozzles. 58 Young trees need continuous protection from ACP feeding and pathogen transmission owing to their frequent flushing pattern and ACP colonization. Soil application of systemic insecticides offers continuous protection and is a widely followed practice.…”