Protective and curative grape black rot control potential of pyraclostrobin and myclobutanil

Abstract

Strobilurin or triazole type fungicides have proven to be very effective in strategies to control grape black rot (causal agent: Guignardia bidwellii) due to their combined protective and curative activities. However, differences in their long-lasting protective capacity or in the limitation of the time frame for curative treatments have not yet been clearly described regarding this pathogen. To address these issues, trials with artificial inoculation were conducted using one representative of each group, pyraclostrobin and myclobutanil on leaves of potted vines as well as on berries of field grown vines. It could be demonstrated that pyraclostrobin possesses excellent pre-infection as well as post-infection activities on both, leaves and berries. Post-bloom, pyraclostrobin was able to completely inhibit infections on berries up to three weeks after application. Full curative control of developing black rot infections was achieved for up to 85% of the total incubation period. Myclobutanil turned out to be of limited protective activity. If applied the day prior to inoculation, the efficacy level reached around 90% but decreased continuously with increasing temporal distance between application and inoculation. However, curative applications of myclobutanil in the first half of the incubation period completely prevented symptom development on leaves as well as on berries. Due to their combined reach-back and forward activity to control black rot, both, pyraclostrobin as well as myclobutanil can be recommended in practical viticulture, especially in the most susceptible period between flowering and berries beginning to touch. Pyraclostrobin offers an exceptional protective and long-lasting curative potential, whereas myclobutanil is most effective in post-infection use.

A Cumulative Degree-Day-Based Model to Calculate the Duration of the Incubation Period of Guignardia bidwellii

“…Combined with this knowledge, the present incubation period model could present a tool for a more targeted timing of fungicides with postinfection activity, such as triazoles or strobilurines (2,4,18), because trials on leaves and clusters had shown that post-infection fungicide applications made when up to 50% (myclobutanil) or even 85% (pyraclostrobin) of the incubation period had passed were able to virtually suppress the occurrence of symptoms, regardless of the duration of the incubation period (12). However, if possible, curative applications should be placed as close as possible to observed infection events to guarantee optimal success.…”

Chemical Management of Alternaria Leaf Blight of Sunflower

“…The efficiency of the above-mentioned fungicides against ALB of sunflower, some researchers observed the effectiveness of test fungicides against other fungal pathogens of various crops. For example, Hoffman and Wilcox (2003) and Molitor et al (2011) reported that Myclobutanil gave the best effect against grapevine powdery mildew (Uncinula necator) and grapevine black rot (Guignardia bidwellii). It also gave the best control of diseases of stone fruit, cereal seeds, cucurbits sugar beet, rose and cucurbits.…”

Epidemiology, identification and disease management of grape black rot and potentially useful metabolites of black rot pathogens for industrial applications – a review

“…Several studies showed that P. ampelicida is highly susceptible towards DMIs (Spotts, 1977 a , 1979; Ellis et al ., ; Hoffman & Wilcox, ; Molitor et al ., 2011 a ) – especially if they are applied curatively. Some DMIs turned out to have limited protective activity (Molitor, ; Molitor et al ., 2011 a ). On an average of 12 field trials, different DMI based spraying regimes reached an efficiency level of 98 ± 3% (Table ).…”

“…Active ingredients belonging to the fungicide class of dithiocarbamates, such as metiram, mancozeb and propineb, showed in several trials a good and long‐lasting activity against black rot – especially if they are applied as protectants (application prior to infection) (Spotts, 1977 a ; Tomoiaga & Comsa, ; Molitor et al ., 2011 a )). However, their curative (post infection) activity is poor (Spotts, 1977 a ; Molitor, ).…”

“…Furthermore, P. ampelicida is highly susceptible to QoIs (Hoffman & Wilcox, ; Northover, ; Molitor, ;). Molitor et al . (2011 a ) demonstrated that the QoI pyraclostrobin possesses excellent pre‐infection as well as post‐infection activities on both, leaves and berries.…”