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Title: Effect of surfactant concentration on the spreading properties of pesticide droplets on Eucalyptus leaves

Author
item LIN, HUAN - Nanjing Forestry University
item ZHOU, HONGPING - Nanjing Forestry University
item XU, LINYUN - Nanjing Forestry University
item Zhu, Heping
item HUANG, HUANHAU - Nanjing Forestry University

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2016
Publication Date: 12/30/2016
Citation: Lin, H., Zhou, H., Xu, L., Zhu, H., Huang, H. 2016. Effect of surfactant concentration on the spreading properties of pesticide droplets on Eucalyptus leaves. Biosystems Engineering. 143: 42-49.

Interpretive Summary: The leaf surfaces attacked by pests vary with the type of insect or disease. Different insects have their favorite feeding locations on leaves. The behavior of pesticide spray droplets on plant surfaces contributes to controlling the physiological and biological processes. The leaf morphology which varies with the plant variety and species affects the formation of droplet deposition and retention on leaf surfaces. In this research, residual patterns of single droplets and their spread areas at different locations on leaf surfaces were investigated. Spray solutions contained various classes of adjuvants and pesticides at different concentrations. Test results demonstrated that the use of appropriate adjuvants and concentrations improved droplet deposition quality on waxy leaves, thereby increasing pesticide effectiveness to control insects, diseases as well as weeds. This quantitative information will help spray applicators to increase pesticide application efficiency economically with significant reduction in off-target losses.

Technical Abstract: The area wetted by 500-µm diameter droplets of pesticide and deionised water placed at different positions on Eucalyptus urophylla × E. grandis (E.u × E.g) and Eucalyptus tereticornis (E.t) leaves was determined at an air temperature of 30 °C and a relative humidity of 60%. Dimethyl dichlorovinyl phosphate (DDVP), and efficient cypermethrin (EC) were diluted 1000 times in deionised water. Solutions of pesticides were prepared with surfactant concentrations (SC) of 0.1%, 0.25%, 0.5%, and 1%. For comparison SC solutions with water and deionised water were also used. Droplet deposition positions were located in the interveinal area, midrib, and secondary vein on both adaxial and abaxial surfaces. Without surfactant, all droplets remained nearly spherical and did not spread on the leaf surfaces. With surfactant, the deionised water and pesticide droplets had distinct spreading properties. For deionised water, both the wetted area and spread effectiveness peaked at 0.1% SC, while for pesticide droplets the wetted area peaked at 1% SC. However, the optimum SC was 0.25%. Droplets spread more on E.t leaves than on E.u × E.g leaves. The adaxial surface had better wettability than the abaxial surface. For pesticide droplets, the wetted area was a minimum on the midrib and the wetted area on the secondary vein was slightly larger than that on the interveinal area.