Sensitivity of the Colletotrichum acutatum Species Complex From Apple Trees in Brazil to Dithiocarbamates, Methyl Benzimidazole Carbamates, and Quinone Outside Inhibitor Fungicides

Abstract

Glomerella leaf spot (GLS) and bitter rot (BR) on apples are often caused by Colletotrichum acutatum in Paraná State, Brazil. GLS control is difficult because of its rapid development, with an incubation period of only 2 days under favorable conditions. Therefore, producers use successive fungicide applications every season; however, failure to control GLS has been commonly reported. The objectives of this study were to determine the sensitivity of isolates of the C. acutatum species complex obtained from apple orchards in Brazil to mancozeb, thiophanate-methyl, and azoxystrobin fungicides. Isolates from the different parts of the plant (leaves, flowers, buds, and twigs) and cultivars (Gala and Eva) showed different levels of sensitivity to mancozeb, thiophanate-methyl, and azoxystrobin. For mancozeb, the frequencies of isolates were 25% highly resistant, 50% low-resistance, and 25% sensitive. For thiophanate-methyl, the frequencies of isolates were 72.2% highly resistant, 11.1% resistant, and 16.7% moderately resistant. For azoxystrobin, the frequencies of isolates were 11.1% highly resistant, 5.6% resistant, and 83.3% sensitive. Interestingly, no mutations in the β-tubulin and cytochrome b genes were observed in any of the isolates resistant to thiophanate-methyl and azoxystrobin fungicides.

Use of Essential Oils for the Control of Anthracnose Disease Caused by Colletotrichum acutatum on Post-Harvest Mangoes of Cat Hoa Loc Variety

“…It has been known to be especially destructive on fruits such as papaya and capsicum, strawberry, citrus, apple, olive, cranberry, blueberry, and mango. This fungal species has been demonstrated to be the most infectious, because it is resistant to a wide range of fungicides, namely, carbendazim [ 57 ], benomyl and copper oxide [ 59 ], quinone outside inhibitors [ 61 ], and mancozeb and thiophanate-methyl [ 62 ].…”

Etiology and epidemiology of diseases caused by Colletotrichum spp. in persimmon, apple, peach, and grapevine

“…For apple trees, chemical control in many Brazilian regions is s� ll dependent on the use of mul� site fungicides such as dithiocarbamates, and for site-specifi c fungicides, such as those from the MBC and QoI groups, isolates with low sensi� vity have already been found (Moreira et al 2019a). In Brazil, 15 ac� ve ingredients are registered for the control of Colletotrichum spp.…”

“…Diseases caused by Colletotrichum species cause damage to several crops. The fungus can cause diff erent symptoms depending on the crop, such as intense defolia� on, blossom blight, branch lesions, fruit rot and premature fruit drop, leading to significant reduc� ons in yield over the years (Dowling et al 2020;Moreira et al 2019a;.…”

“…Research has shown that Colletotrichum species belonging to the same complex or not may present diff erent interac� ons with the host, diff erences in life cycle (da Silva et al 2020) and occurrence of cross-pathogenicity between species from diff erent hosts (Bragança et al 2016;Eaton et al 2021). Furthermore, diff erent levels of sensi� vity to fungicides have been reported among Colletotrichum species (Dowling et al 2020;Moreira et al 2019a;.…”

Sensibilidad y resistencia a fungicidas de <i>Cercospora kikuchii</i>, agente causal del tizón de la hoja y mancha púrpura de la semilla de la soja

“…Durante los últimos diez años, su uso ha aumentado significativamente en Brasil para el control de la RAS (Carmona et al, 2017a). Aunque el riesgo de desarrollar resistencia al mancozeb se considera bajo (Carmona et al, 2018b), se ha reportado la aparición de varias especies de hongos tolerantes o resistentes en varios cultivos (Aguilar et al, 2014;Moreira et al, 2019;Yang et al, 2019). Por lo tanto, no se puede confirmar si las especies de Cercospora aquí evaluadas se consideran resistentes o naturalmente insensibles al mancozeb, ya que en Argentina este fungicida nunca se ha utilizado en el cultivo de soja para el control de ninguna enfermedad.…”