Nozzle and Carrier Application Effects on Control of Soybean Leaf Spot Diseases

Abstract

Increased soybean foliar disease potential has heightened grower interest in fungicide application techniques. Application field trials comparing application rate [187 vs. 112 L/ha (20 vs. 12 gal/acre)], nozzle style (twin-orifice; single-orifice) and spray quality (fine vs. medium and coarse spray quality), and application technique (with and without air-assist) along with an unsprayed check were done at two locations over two years. Fungicide deposition (coverage and droplet size) and disease severity in the bottom, middle, and top parts of the plant canopy, and soybean yield were measured. Fungicide deposition coverage reduced from the top (8%-18%) to the middle (4%-8%) to the bottom (1%-4%) of the canopy. Coverage was less affected by application treatment, however in wider rows [76-cm (30-in.)] coverage increased with the high-rate and air-assist treatments when spray quality was near the border between fine and medium. Conversely, in narrow rows [38-cm (15-in.)], least coverage was obtained with fine droplets produced by hollow-cone tips on an air-assisted sprayer. Size of droplets deposited generally followed predictions suggested by spray quality. Few disease severity differences were observed. Yield was unaffected by treatments sprayed during late reproductive stages (late R3-R5) of the soybean plant.

News Soybean Sowing Arrangements on Spray and Control of Asian Rust

“…The addition of the soybean oil methyl-ester adjuvant to the spray may reduce the volumetric median diameter of the spray droplets relative (Sasaki et al, 2015). The reduction of the diameter of the droplets in turn provides greater penetration of the spray droplets in the canopy of the soybean crop (Hanna, Robertson, Carlton, & Wolf, 2009).…”

Journal of Plant Protection Research

“…WSP is a specific type of paper coated with bromoethyl blue, a dye that appears yellow, but turns blue when hydrated by water-containing droplets impacting the coated paper collectors (Turner and Huntington 1970). The use of WSP for characterization of sprays in the field has been on-going for 45 years (Turner and Huntington 1970) and is the most widely used collector type for canopy penetration studies (Knoche 1994;Derksen et al 2008;Wolf and Daggupati 2009;Hanna et al 2009;Derksen et al 2014).…”

“…Canopy penetration is the ability of sprayed droplets to move through a canopy to provide adequate control of pests. Previous studies have examined canopy penetration in several cropping systems to identify which application techniques and technologies maximize canopy penetration (Knoche 1994;Zhu et al 2004;Derksen et al 2008;Hanna et al 2009;Derksen et al 2014;Creech 2015;Ferguson et al 2016). These studies observed that coarser sprays improved canopy penetration within several crop canopy types.…”

“…Only the trends from these studies have been compared since different methods to analyze droplet deposition were used. WSP collectors were used in most of these studies (Knoche 1994;Zhu et al 2004;Derksen et al 2008;Wolf and Daggupati 2009;Hanna et al 2009;Derksen et al 2014). One study used a fluorescent tracer dye and Mylar collectors and rinsed them, obtaining droplet deposition results based on the fluorescence of each collector (Creech 2015).…”

Construction and Practical Application of a Canopy Opener Device

“…Among the pesticides that are used to protect crops of economic interest, fungicides and insecticides have greater difficulty reaching their targets than herbicides because insects and fungi are often present in regions of the plant where the spray droplets cannot readily penetrate the barriers created by the top leaves. The penetration of droplets through the leaf canopy is more difficult as the leaf area indices increase HANNA et al, 2009). …”