Fluorescent Dye Paper-Based Method for Assessment of Pesticide Coverage on Leaves and Trees: A Citrus Grove Case Study

Abstract

Crop disease management depends on efficient and adequate pesticide distribution to reduce pest population. Instrument-based methods to evaluate the spatial distribution of pesticides are available, but they are not field-compatible because of instrument size, cost, and extensive sample preparation. The current gold standard of water-sensitive papers is field-compatible; however, these papers often produce false positives due to reaction with water from sources other than the pesticide mixture. Thus, we developed a novel method in which a fluorescent dye is sprayed over a crop with circles of filter paper (samplers) attached to the leaves. After collection, a lightbox is used to take pictures of the samplers, and an algorithm analyzes each image for percent coverage to visualize the pesticide distribution within the crop. Our method produces results quickly and inexpensively compared to current methods and can be applied to any crop to inform best pesticide application strategies.

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

“…Water-sensitive papers and dyes allow growers to visually see the sprayed droplets on a leaf. 18 This presence of dye or color change is assumed to translate to the presence of insecticide. 14,[19][20][21] Citrus trees have large total foliar surface areas 20 and leaves are often wet in humid environments, like Florida's conditions.…”

“…Therefore, distributing large water-sensitive papers throughout a wet citrus tree often results in misrepresentations of insecticide presence. 18 Some studies investigated spatial distribution in more depth, exploring canopy penetration to a variety of crops including wheat, peppers, onion, tomatoes, oat, and bay laurel. These spatial distribution results of insecticides may be especially inadequate for citrus trees due to their larger canopies and total foliar surface area.…”

“…Currently, the most common ways to assess insecticide coverage to crops in the field is to implement fluorescent dyes or water‐sensitive papers that change color when contacted with water. Water‐sensitive papers and dyes allow growers to visually see the sprayed droplets on a leaf 18 . This presence of dye or color change is assumed to translate to the presence of insecticide 14, 19–21 .…”

“…Citrus trees have large total foliar surface areas 20 and leaves are often wet in humid environments, like Florida's conditions. Therefore, distributing large water‐sensitive papers throughout a wet citrus tree often results in misrepresentations of insecticide presence 18 . Some studies investigated spatial distribution in more depth, exploring canopy penetration to a variety of crops including wheat, peppers, onion, tomatoes, oat, and bay laurel.…”

Microfluidic Paper-Based Analytical Devices: From Design to Applications

“…(B) Paper-based sensor for detecting pesticides in crop samples: (i) water-sensitive paper, (ii) Lightbox with Raspberry Pi, and (iii) illustration of the method. Adapted with permission from ref . Copyright 2020 American Chemical Society.…”