Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu and Karen Rane, Plant Diagnostician, University of Maryland rane@umd.edu
There have been some strange happenings in vegetable/fruit fields this season. The latest one is with cantaloupe fruit. The fruit looks good when examining it from the outside, but cutting it open reveals an interior that has a dark, wet appearance in the fruit’s wall between the outer rind and the seed cavity (Figure 1). I first thought this was possibly a disease such as charcoal rot or black rot, but Karen Rane could find no disease-causing organisms in the damaged areas of the fruit or anywhere else in the fruit. She then came up with something called glaze or glassy fruit.
Glaze fruit is an abiotic problem that is characterized by the glassy appearance of part of the cantaloupe flesh. This spot then quickly takes on a wet appearance and over time begins to break down becoming soft and watery. This damaged area then gives off an alcoholic fermentation odor. Often times, the outside of the fruit will remain clean, with no symptoms (Figure 2), but inside the fruit the watery rot is spreading. However sometimes a dark, greasy looking spot can become visible on the surface of the fruit at a very advanced stage of decline (Figure 3).
I would like to say that there is a good understanding as to what causes this decline in the fruit, but there is little definitive information out there about it. Among the factors likely to promote the appearance of this condition are, an excessive fruit load, cool weather that quickly turns hot, very dry soil conditions which promote poor root development, a deficiency in calcium and potassium and cultivar sensitivity. Bottom line, the causes are stressful weather conditions that affect some varieties more than others. Fortunately, this malady disappeared from this field after this harvest.
Fig. 1 Dark greasy or wet-looking areas of cantaloupe flesh
Fig. 2 Fruit with damaged flesh, but outside looks good
Fig. 3 Fruit with outside surface with dark areas
