Vattenkvaliténs påverkan på bladmögelsfungicider : bekämpningseffekt i laboratoriemiljö

Abstract: The majority of pesticides used in agriculture is mixed with water prior to application and the rate of water widely exceeds the rate of pesticides. Water from different sources has different characters such as pH, water hardness (°dH) and iron content. That these different characters affect some sensitive pesticides is well known. Especially the glyphosate herbicide is known to have reduced performance when mixed with water containing high levels of positively charged cations such as Ca²⁺, Mg²⁺ and Fe²⁺ resulting in less effectiveness on weeds. Also the group of insecticides called pyrethroides are known to be sensitive to high pH-values causing rapid degradation and reduced effect on the target. Reduced pesticidal effect is negative for both farmers and environment since it may lead to higher pesticide rates to a higher cost. To find out if fungicides effect on Phytophthora infestans is affected by different water quality aspects this study was made. The three common fungicides Infinito, Ranman Top and Revus Top were tested with seven different water types, all based on distilled water, in laboratory conditions. The study showed that there is a difference in infection between the different water types. The biggest reduction of infections appeared when acidic distilled water or alkaline water with 2mg Fe/L was used. This reduction was probably not an effect of improved fungicide performance but rather an effect of the water being toxic to P. infestans. The other types of water showed some differences between the fungicides. It’s hard to tell how water quality affected fungicide performance in this study due to the strong effects that probably was caused by water toxicity to the pathogen. The results from this study may not easily be transferred to field conditions because of the way different methods used in laboratory conditions.