Melon Research Paper

Diseases of melon ( Cucumis melo ) in Arizona
Alternaria leaf spot
Alternaria leaf spot is caused by the fungus Alternaria. The fungus produces dark, multicelled spores on host tissue only when there is substantial moisture, usually during summer rains. The spores are easily carried in wind and splashing water and infect only the leaves. Brown necrotic spots appear on the leaves wherever spores germinate and infect leaf tissue (photo 1). Spots are small at first then may enlarge and coalesce to form circular lesions with visible concentric rings (photo 2).
Disease severity is dependent on varietal susceptibility and environmental conditions. Extended periods of moisture and warm temperatures favor disease development. It is rarely a problem
Plants may be infected when they are young, but symptoms usually do not appear until vines are mature and fruit are developing (photo 1). Foliage may have necrotic areas in the leaves and a progressive decline in the entire crown (photo 2). Tan lesions are often observed on roots, and, in the later stages of disease only, small black specks appear (photo 3). These specks are the sexual reproductive stage of the fungus that contain large black spores - thus the species name cannonballus (photo 4). These spores are commonly found in many different soils, and the fungus seems to be indigenous to certain semiarid
These are listed with their host range, symptoms, vector and available control strategies:
Papaya ringspot virus (Potyviridae, Potyvirus, ssRNA) (Watermelon mosaic virus 1) infects cucurbits only. It causes mottled and mosaic leaves, blisters and distortion. It is sap transmissible and is carried non-persistently in aphids; it is not seed borne. There is tolerance in some varieties.
Watermelon mosaic virus (Potyviridae, Potyvirus, ssRNA) (Watermelon mosaic virus 2) infects cucurbits, many weed species and especially legumes; it causes variable symptoms including mottled and mosaic leaves and stunting (photos 1 and 2). It is sap transmissible and is carried non-persistently in aphids; it is not seed borne. There is tolerance in some varieties. It occurs throughout Arizona wherever cucurbits are grown.
1 2
Zucchini yellows mosaic virus (Potyviridae, Potyvirus, ssRNA) infects cucurbits but little is known of other off-season hosts. It causes severe mosaic, shoe-stringing, stunting, and blisters (photo 1). It is sap transmissible and is carried non-persistently by aphids; it is not seed borne. There is tolerance in some