Gummy stem blight can be distinguished from cucurbit anthracnose by the larger leaf spots, larger lesions that encircle petioles, and crown cankers. Water-soaking may also be visible on the leaf underside on main veins that pass through lesions.Ĭonstricting lesions at the apex or the base of a petiole or on the midrib of a leaf may cause the entire leaf to collapse (Fig. Actively expanding lesions on leaves, petioles, and pedicels often are water-soaked, as the pathogen produces cell wall-degrading enzymes, in particular polygalacturonase (27) (Fig. 1).Īs leaf spots expand, they coalesce, which results in leaf blighting (Fig. On most hosts, more than half of the spots start at the margins of leaves or extend to the margins (Fig. Leaf spots generally are the symptom noticed first and are the symptom most often used to diagnose the disease. Gummy stem blight symptoms affect all above-ground vegetative and reproductive parts of cucurbits, including leaves, petioles, vines, stems, tendrils, pedicels, flowers, peduncles, fruit, and seed (5,11). recently was renamed Stagonosporopsis cucurbitacearum (Fr.) Aveskamp, Gruyter & Verkley based on DNA sequence data that divided Phoma species into a number of genetically distinct clades (1).Ĭurrent taxonomic information is available at Fungal Databases at the Systematic Mycology and Microbiology Laboratory, USDA-ARS () and Mycobank ( The taxonomic treatment of the genus Didymella by Corlett includes a useful summary of primary literature (6).

However, it is clear from Rehm’s original note that he based his name on Auerswald’s species name, published in 1869, and considered Fuckel’s identical species name for this fungus, published in 1870, a synonym (19). bryoniae (Fuckel) Rehm, since this is the author citation published by Saccardo in 1882. Note that some taxonomists use the author citation D. bryoniae (Auersw.) Rehm published in 1881 is (Mycobank, As of 1 January 2013, changes to the International Code of Botanical Nomenclature specify that each fungus is to be known by only one name, even if it has teleomorphic (sexually reproducing) and anamorphic (asexual) states.ĭ. were used for the teleomorph and anamorph names, respectively.ĭomain Eukaryota, Kingdom Fungi, Phylum Ascomycota, Subphylum Pezizomycotina, Class Dothideomycetes, Subclass Pleosporomycetidae, Order Pleosporales, Family Didymellaceae, Genus Didymella, Species D. Walker and Ascochyta cucumis Fautrey & Roum. In the older literature, Mycosphaerella melonis

Stagonosporopsis cucurbitacearum (Fr.) Aveskamp, Gruyter & Verkley Phoma cucurbitacearum (Fr.:Fr.) Sacc. Gummy stem blight and black rot are caused by the ascomycete fungus Didymella bryoniae (Auersw.) Rehm (19), which is the name of the teleomorph. Black rot also affects watermelon when foliar blight is severe (27). The fruit of butternut squash, jack-o-lantern pumpkin, ornamental gourds, muskmelon, and greenhouse cucumber are the most susceptible (3,23,26,27). There is considerable variation in fruit susceptibility to black rot within C.

Susceptibility of cucurbit crops to black rot differs from susceptibility to foliar blight and crown cankers. pepo, jack-o-lantern pumpkin and ornamental gourds tend to be more susceptible to foliar blight than squashes. C. The following list is arranged in an approximate order of susceptibility to both the foliar blight and canker phases of gummy stem blight, starting with the species that are the most susceptible: muskmelon, honeydew melon, and other melons (Cucumis melo subsp. melo) watermelon (Citrullus lanatus var. lanatus) cucumber, slicing and pickling (Cucumis sativus) Hubbard squash, giant pumpkin, buttercup squash, turban squash (Cucurbita maxima) jack-o-lantern pumpkin, ornamental gourds, acorn squash, summer squash, and zucchini (Cucurbita pepo) and butternut squash and tropical pumpkin (Cucurbita moschata) (14). Rankings of hosts also differ depending on whether susceptibility to foliar blight, crown, stem and vine cankers, or fruit rot is considered. The fruit rot phase is often called black rot.Īll commonly cultivated cucurbits (members of the botanical family Cucurbitaceae) are susceptible to gummy stem blight, although the degree of susceptibility differs among species and horticultural types. Diagnostic guide for gummy stem blight and black rot on cucurbits. Keinath, Clemson University, Coastal Research and Education Center, Charleston, SC 29414-5239Ĭorresponding author: Anthony P. Diagnostic Guide for Gummy Stem Blight and Black Rot on CucurbitsĪnthony P.

Gummy stem blight cucumber treatment