Effect of Timing of Fungicide Applications on Development of Rusts on Daylily, Geranium, and Sunflower

Abstract

Integrated disease management should provide the most effective means of controlling rusts on ornamental crops over time, and fungicides are an important component of an integrated rust management program. Proper timing of fungicide applications is critical for effective disease management; however, information about application timing is lacking for rusts on ornamental crops. The objective of this study was to determine how fungicides affected rust development on daylily, geranium, and sunflower plants when applied several days before or after inoculation. Five fungicides registered for use against rusts on ornamental crops were evaluated: the strobilurin azoxystrobin; three sterol biosynthesis inhibiting fungicides—myclobutanil, propiconazole, and triadimefon; and the broad spectrum protectant chlorothalonil. All five fungicides significantly reduced lesion development by rust pathogens on daylily, geranium, and sunflower plants when these compounds were applied preventatively up to 15 days before inoculation and infection with a few exceptions (e.g., propiconazole on geranium and triadimefon on sunflower). Curative activity, which resulted from fungicide application after inoculation, was observed for the three rusts with some products (azoxystrobin on all three plants and myclobutanil, propiconazole, and triadimefon on geranium) when applied up to 7 days postinoculation. In general, fungicide efficacy with several of the products decreased as the time from application to inoculation (preventative activity) or inoculation to application (curative activity) increased.

Curative and Eradicative Effects of Fungicides

“…Triadimefon significantly reduced lesions caused by Puccinia pelagonii-zonalis on geranium plants when applied up to seven days after inoculation of plants with the fungus (Mueller et al, 2004). The same fungicide significantly reduced lesions of another rust, Puccinia hemerocallidis on daylily, when applied up to five days after inoculation, while significant effect of this triazole fungicide on sunflower rust, Puccinia helianthi, was observed only up to one day after inoculation of plants with the fungus (Mueller et al, 2004). Applied one day after inoculation of tomato with Alternaria solani, difenconazole showed more than 90 % of disease control, while control level decreased to 60 % when the same fungicide was applied two days after inoculation of plants (Dahmen & Staub, 1992).…”

“…The highest reduction of Rhizoctonia solani foliar blight on inoculated soybean plants was achieved with pyraclostrobin, followed by azoxystrobin, trifloxystrobin, difenconazole, bromuconazole, tebuconazole, benomyl, thiabendazole, fluazinam and carbendazim (Meyer et al, 2006). Propiconazole and triadimefon significantly reduced Puccinia hemerocallidis severity on daylilies when applied up to five days after inoculation, myclobutanil only up to three days after inoculation, while azoxystrobin significantly reduced disease severity when applied even up to seven days after inoculation of plants with the fungus (Mueller et al, 2004). Superior performance of azoxistrobin compared to myclobutanil, propiconazole and triadimefon was also recorded in postinfection treatments of sunflower plants inoculated with Puccinia helianthi (Mueller et al, 2004).…”

“…Propiconazole and triadimefon significantly reduced Puccinia hemerocallidis severity on daylilies when applied up to five days after inoculation, myclobutanil only up to three days after inoculation, while azoxystrobin significantly reduced disease severity when applied even up to seven days after inoculation of plants with the fungus (Mueller et al, 2004). Superior performance of azoxistrobin compared to myclobutanil, propiconazole and triadimefon was also recorded in postinfection treatments of sunflower plants inoculated with Puccinia helianthi (Mueller et al, 2004). An influence of different pathogens on curative effects of fungicides can be showed in examples with the same fungicides applied as curative treatments on plants affected with different diseases.…”

“…None of the fungicides was effective in postinoculation treatments on melanose, another disease of citrus, caused by the fungus Diaporthe citri (Bushong & Timmer, 2000). Triadimefon significantly reduced lesions caused by Puccinia pelagonii-zonalis on geranium plants when applied up to seven days after inoculation of plants with the fungus (Mueller et al, 2004). The same fungicide significantly reduced lesions of another rust, Puccinia hemerocallidis on daylily, when applied up to five days after inoculation, while significant effect of this triazole fungicide on sunflower rust, Puccinia helianthi, was observed only up to one day after inoculation of plants with the fungus (Mueller et al, 2004).…”

Eficiência de fungicidas sistêmicos no controle da ferrugem do Eucalyptus

“…No mercado há vários fungicidas eficientes para o controle de ferrugens, como as estrobilurinas e os triazóis (NARUZAWA et al, 2006;GODOY e CANTERI, 2004;MUELLER et al, 2004;CHALFOUN e CARVALHO, 1999). As estrobilurinas têm atividade biológica variada e potencial de controle de ampla gama de fungos.…”