Influence of droplet spectra on the efficiency of contact fungicides and mixtures of contact and systemic fungicides

Abstract

The effects of droplet spectra, spray volume, and the addition of an adjuvant to the spray solution against Phytophthora infestans were evaluated using contact fungicides, mixtures of contact and systemic fungicides, and a contact fungicide + an adjuvant. Six droplet spectra, ranging from VMD = 183 µm to VMD = 939 µm, were used. The spray volumes were 300, 450 and 600 l/ha for the contact fungicides, and 300 l/ha was used for the mix of contact with systemic fungicides. No significant differences in efficiency were observed between different droplet spectra when used for the mix of contact with systemic fungicide treatments. However, the efficiency of treatments with a contact fungicide significantly increased with smaller droplet spectra. The larger droplet spectra required larger spray volumes for greater efficiency. The addition of the adjuvant (pinolene, 96%) to the spray solution of the contact fungicide caused the efficiency to be similar for all droplet spectra. The effect of droplet spectra is more pronounced in contact compounds. The translocation of the systemic compounds and the ability of the surfactant to improve the coverage with contact compounds may be the main mechanisms that counteract the effects of larger droplet spectra and lower leaf coverage.

Field evaluation of an unmanned aerial vehicle (UAV) sprayer: effect of spray volume on deposition and the control of pests and disease in wheat

“…Unfortunately, previous studies suggest that such a relationship between fungicidal and droplet size is only found with contact fungicides. Prokop and Veverka examined the droplet spectra on the efficacy of contact fungicides, and mixtures of contact and systemic fungicides. They discovered that the efficiency of treatments with a contact fungicide significantly increased with the number of spray deposits.…”

Development of a rapid methodology for biological efficacy assessment in banana plantations: application to reduced dosages of contact fungicide for Black Leaf Streak Disease (BLSD) control

“…In addition, spray efficacy through physical deposition can be determined more easily and rapidly immediately after spray application, compared with the biological efficacy assessment during the whole cropping cycle. These aspects become more important considering that contact fungicides are more sensitive to spray deposition than the systemic mode of action …”

“…In many cases, the biological efficacy of the active substance or dosage of the fungicide is tested despite the influence of the spray quality . Studies from Washington on BLSD and by Prokop and Veverka on potato Phytophtora infestans are notable exceptions.…”

“…These aspects become more important considering that contact fungicides are more sensitive to spray deposition than the systemic mode of action. 23 Other authors have studied biological efficacy in the field by measuring the evolution of pest populations or plant tissue damage. 24 Measurements of the effectiveness of fungicide applications for disease control are often carried out in the field with natural infestations.…”

Effect of the spray volume adjustment model on the efficiency of fungicides and residues in processing tomato

“…On the contrary systemics are less influenced than contact plant protection products (Wise et al, 2010). Increased coverage of plant surface is considered to be the factor responsible for higher effectiveness of mixes of contact fungicides with surfactants against PLB (Prokop & Veverka, 2006). Organosilicone surfactants seem to be one of the most effective wetting agents (Nikolov et al, 1998).…”