Submitted to: Scanning
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2008
Publication Date: 1/26/2009
Citation: Krause, C.R., Derksen, R.C., Horst, L., Zhu, H., Zondag, R. 2009. Effects of Sprayer Configuration of Efficacy for the Control of Scab on Crabapple Using Electron Beam Analysis. Scanning. 31:24-27. Interpretive Summary: Fungus diseases like apple scab result in millions of dollars of nursery crop losses each year. Effective fungicides must be applied to produce aesthetically pleasing plants. Effective delivery of fungicides is crucial to apple scab control. Assessment in past studies involved only macroscopic disease ratings with the unaided eye. A research plot was established by planting 4 replications of 2 susceptible crabapple varieties in a production nursery. The plot was sprayed with 3 different sprayer/nozzle configurations. A high-powered microscope with chemical analytical abilities (electron beam analysis, EBA) was used to actually visualize fungicide residue and fungal structures on leaves sprayed with 3 different sprayers or nozzle types. Freshly treated leaf samples were mounted on sticky dots onto microscope stubs and analyzed with EBA. Direct observation of fungicide treatments verified fungicide spray patterns and presence or absence of fungi based on application methods. More complete knowledge of the fate and behavior of fungicide will lead to reduced pesticide use, better control with less off-target contamination.
Technical Abstract: Foliar diseases like apple scab result in significant economic losses to growers each year. Assessment in past studies involved only macroscopic disease ratings. More complete knowledge of the fate and behavior of fungicide have been needed to reduce pesticide use with less off-target contamination. Field studies were conducted in a production nursery for over 4 years. Two susceptible cultivars of ornamental crab apples, Malus spp. cv. ‘Candied Apple’ and cv. ‘Red Jade’, were sprayed with fungicide using 3 sprayer/nozzle configurations. The fungicide used in this study was a combination of Cu(OH)2 and mancozeb that permitted EBA identification based on the presence of Cu , MN and Zn in the molecule. EBA consisted of cold-field emission scanning electron microscopy and energy dispersive x-ray microanalyzer. Fresh leaf samples were placed on sticky stubs after each fungicide treatment. The presence or absence of fungal structures or fungicide residue was measured. Electron beam analysis permitted direct visualization and identification of the pathogens, morphologically, and chemical characterization of fungicide present. EBA was a viable method to quantify disease control related to fungicide coverage and sprayer configuration.