Eficiência de fungicidas sistêmicos no controle da ferrugem do Eucalyptus

Abstract

Avaliaram-se os efeitos curativo e protetor e o tempo de absorção de fungicidas sistêmicos no controle da ferrugem do eucalipto. Azoxyztrobin, triadimenol, tetraconazole, tebuconazole e epoxiconazole + pyraclostrobin apresentaram 100% de ação curativa quando aplicados até quatro dias após a inoculação. Aplicados após sete dias, apenas azoxystrobin, tebuconazole e epoxiconazole + pyraclostrobin mantiveram o efeito curativo. Aos 10 dias depois da inoculação, os fungicidas reduziram a infecção, mas não controlaram totalmente a doença. Além do efeito curativo, azoxystrobin e triadimenol proporcionaram efeito protetor quando aplicados até 21 dias antes da inoculação de P. psidii. Avaliou-se o tempo mínimo de absorção de azoxystrobin, tebuconazole, triadimenol e trifloxystrobin. Esses quatro fungicidas foram absorvidos pela planta em todos os intervalos testados – 30, 60, 90 e 120 min – e inibiram a infecção de P. psidii em mudas de eucalipto.

Curative and protective effects of systemic fungicides (azoxystrobin, triadmenol, tetraconazole, tebuconazole and the mixture epoxiconazole + pyraclostrobin) against eucalyptus rust were evaluated. To evaluate the curative effect, eucalyptus plants were sprayed with an inoculum suspension (2 x 10 4 urediniospores /mL) and with each fungicide after 0, 4, 7, or 10 days. For the protective effect, the plants were sprayed with each fungicide and with the inoculum suspension after 0, 7, 14, 21, or 28 days. The number of pustules/ leaf, sori/foliar area, and urediniospores/sorus was determined on the first two apical leaves. The best curative effect was achieved with azoxystrobin, tebuconazole, epoxiconazole + pyraclostrobin, and triadimenol, since the number of sori/foliar area and urediniospores/sorus was reduced when applied up to 7 days after inoculation. Regarding protective effect, azoxystrobin and triadimenol were the most effective fungicides, as no pustules formed on the leaves up to 21 days after spray. Azoxystrobin, tebuconazole, triadmenol and trifloxystrobin were absorbed within 30 min after application and no P. psidii infection was detected.