A Review of Corynespora cassiicola and Its Increasing Relevance to Tomato in Florida

Abstract

Corynespora cassiicola is a highly diverse fungal pathogen that can infect more than 500 species of plants, including many economically important crops such as cotton, soybean, tomato, and cucumber. In Florida, the number one vegetable crop by market value are fresh-market tomatoes, which generate nearly half a billion dollars annually. Florida’s subtropical to tropical climate is conducive to infection and development of the target spot pathogen on tomato caused by C. cassiicola. There is no varietal resistance available for target spot of tomato, and preventative fungicide treatments are the primary method for control. In the last decade, C. cassiicola has been more frequently reported by Florida tomato growers, appearing not only more aggressive but also increasingly insensitive to various fungicides. This review brings together the most recent C. cassiicola literature, providing a history and understanding of the immense pathogen diversity and its relevance to tomato. It also provides insight into fungicide resistance development and pathogen survivability, which are important factors in providing effective control recommendations and in understanding the epidemiology of this disease, respectively.

The fungal pathogen Corynespora cassiicola: A review and insights for target spot management on cotton and Soya bean

“…Target spot is a polycyclic disease, and the pathogen has a short reproduction cycle, completing many generations in a season (Agrios, 2005;MacKenzie et al, 2018).…”

“…These fungicides are recommended to be used in combination with fungicides with different modes of action, usually a systemic fungicide, to reduce the selection pressure of one fungicide and inhibit the rise of resistant populations (Brent & Hollomon, 2007;FAO, 2012;Ghini & Kimati, 2000). Multisite or protectant fungicides have been employed to control C. cassiicola on tomato fields in Florida, avoiding $3.5 million USD loss (MacKenzie et al, 2018 Molina et al, 2019). From 2014/2015/2017 in Argentina, one and two applications of epoxiconazole + fluxapyroxad + pyraclostrobin were the best treatments to control target spot on Soya bean, with an average control of 59% and 54% compared with the untreated control.…”

“…Morphologically, colonies of C. cassiicola initially exhibit whitish grey mycelium, turning dark grey with age on PDA (Lopez et al., 2018). Spore morphology varies with the substrate where the spores are collected (MacKenzie et al., 2018). Conidiophores are erect, branched, brown‐colored, single or in clusters with swollen basal cells, 1–20 pseudosepta, 4–11 x 44–135 µm.…”

“…Survival on plant debris is the source of primary inoculum (Almeida et al., 2001). Target spot is a polycyclic disease, and the pathogen has a short reproduction cycle, completing many generations in a season (Agrios, 2005; MacKenzie et al., 2018).…”

“…Soya bean leaves with free moisture and/or relative humidity (RH) of 80% or above favoured foliar infection by C. cassiicola (Godoy, 2015). Corynespora cassiicola from tomato required 16–44 hr of leaf wetness for spore germination and disease development (MacKenzie et al., 2018). Disease severity was positively correlated with 20–30°C and 90% RH (Ortega‐Acosta et al., 2020), while 25–30°C and 95% RH were optimum for spore germination of C. cassiicola isolates from tomato (Dutta et al., 2020).…”