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Pyrenophora tritici-repentis and Drechslera tritici-repentis is a necrotrophic plant pathogen of fungal origin, phylum Ascomycota. [1] The pathogen causes a disease originally named yellow spot but now commonly called tan spot, yellow leaf spot, yellow leaf blotch or helminthosporiosis.
Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves. [2]
A raspberry leaf spot infection initially causes dark green circular spots on the upper side of young leaves, which will eventually turn tan or gray. [3] These spots are typically 1–2 millimetres (0.039–0.079 in) in diameter, but can get as big as 4–6 millimetres (0.16–0.24 in). [4]
The spots merge, eventually forming irregular necrotic patches on the leaves. Leaf spots may be surrounded by a zone of yellow leaf tissue of varying width. Spot may also appear on the leaf sheaths, necks and heads of the plant. Heavily infected leaves dry up completely, and infections on the flag leaf during kernel filling are the most serious.
The lesions found in Northern corn leaf blight are more acute if the leaves above the ear are infected during or soon after flowering of the plant. [4] In susceptible corn hybrids, lesions are also found on the husk of ears or leaf sheaths. In partially resistant hybrids, these lesions tend to be smaller due to reduced spore formation.
Leaf scorch (also called leaf burn, leaf wilt, and sun scorch) is a browning of plant tissues, including leaf margins and tips, and yellowing or darkening of veins which may lead to eventual wilting and abscission of the leaf.
According to Chiquita, Yelloway One is the first edible banana to have a combined resistance to these two diseases. "The success of Yelloway's breeding program in producing a banana variety with ...
Prevention is the best option for management of gray leaf spot as hyphae on plant debris is the primary source of inoculum. [1] There are various cultivars of St. Augustine grass, perennial ryegrass and tall fescue on the market that have variable resistance to gray leaf spot but none are confirmed as completely resistant.