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Peach scab, also known as peach freckles, is a disease of
The disease affect most stone plants including peaches, apricots and plums. The symptoms can generally be found in three major parts of plant: fruits, twigs, and leaves. The symptoms on leaves and twigs are often considered as the least notable. Infected leaves initially show small and green colored lesions on under the leaves. They progress into yellowish brown and eventually appear as dark brown or black spots.
Twig lesions start to form on green young stems. The lesions are about 3 up to 6.5 mm in diameter size. They usually first have reddish brown colors then which will turn into darker colors as they enlarge to an oval shape of 3 x 6mm approximately.
About six weeks after petals are fallen, the first and most notable and serious symptoms appear on fruits. Spots, which generally range from 1 to 2 mm in diameter size, are formed on the end of stem. They gradually change its color into dark green or black and grow about a few millimeters in diameter. As they enlarge, yellow circles will form around the velvety dark green spots. The spots have raised appearance on fruits instead of sunken figures which can be found most prevalently in other fungal infections. In some severe cases, fruits may be stunted or opened and exposed to further infection by airborne microorganisms.
stone fruit
In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part ( exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kernel ...
s caused by the fungi '' Cladosporium carpophilum''. The disease is most prevalent in wet and warm areas especially southern part of the U.S. as the fungi require rain and wind for dispersal. The fungus causes scabbing, lesions, and defoliating on twig, fruit, and leaf resulting in downgrade of peach quality or loss of fruits due to rotting in severe cases.
Symptoms
The disease affect most stone plants including peaches, apricots and plums. The symptoms can generally be found in three major parts of plant: fruits, twigs, and leaves. The symptoms on leaves and twigs are often considered as the least notable. Infected leaves initially show small and green colored lesions on under the leaves. They progress into yellowish brown and eventually appear as dark brown or black spots.
Twig lesions start to form on green young stems. The lesions are about 3 up to 6.5 mm in diameter size. They usually first have reddish brown colors then which will turn into darker colors as they enlarge to an oval shape of 3 x 6mm approximately.
About six weeks after petals are fallen, the first and most notable and serious symptoms appear on fruits. Spots, which generally range from 1 to 2 mm in diameter size, are formed on the end of stem. They gradually change its color into dark green or black and grow about a few millimeters in diameter. As they enlarge, yellow circles will form around the velvety dark green spots. The spots have raised appearance on fruits instead of sunken figures which can be found most prevalently in other fungal infections. In some severe cases, fruits may be stunted or opened and exposed to further infection by airborne microorganisms.
Disease cycle
As a part of asexual fungi groupFungi imperfecti
The fungi imperfecti or imperfect fungi, are fungi which do not fit into the commonly established taxonomic classifications of fungi that are based on biological species concepts or morphological characteristics of sexual structures because th ...
, ''Cladosporium carpophilum'' does not produce sexual spores but produce conidia, mycelium, and chlamydospsores for its dispersal and survival structures. Conidia produced during spring and summer are the major source for primary inoculum. Another possible source for primary inoculum could be infected leaves fallen on the ground however the importance of this mechanism is unknown.
Conidia produced under the favorable conditions are spread from primary source by wind or rain to infect developing young susceptible twigs, fruits, or leaves of peach plant. Fruit infections take place during early development since conidia begin to produce and peak around calyx split and bloom. Once conidia are successfully landed on susceptible hosts, they form germ tubes which will become spore-bearing conidiophores. This step requires three sequential stages: sporophore
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