Upper left: Botrytis blight in a tulip leaf; large blight lesions generally develop gray mold spores. Upper right: White streak in gladiolus leaves, a virus disease. Lower left: Botrytis sclerotic on the dry tulip bulb carry the fungus into old and new fields. Lower right: Iris bulbs attacked by the bulb and stem nematode.

ASTER YELLOWS, a common virus disease well known in a wide range of plants, also affects gladiolus. Diseased gladiolus develop green flowers and uniformly straw-yellow leaves in Eastern States. The plants usually shrivel and die down rapidly after the symptoms appear. We proved in 1948 that aster yellows causes these effects. The disease is damaging but usually is infrequent in gladiolus, even in areas of high intensity of aster yellows. The reason for this low prevalence in gladiolus is unexplained, for the six-spotted leafhopper, the vector of the virus, feeds readily on gladiolus.

A DISEASE called grassy-top developed in up to 50 percent of the plants of some commercial fields of gladiolus in Florida and Alabama in 1952. The corms that gave rise to the disease were all grown the previous season in one locality in Oregon. Affected plants developed several weak yellow shoots instead of the single vigorous shoots of normal plants. Roots also were thin and weak. Corms had rough, hard bases, small warts at the nodes, and enlarged and irregular cores. From such grassy-top gladiolus the six-spotted leafhopper transmitted western aster yellows to China aster, celery, and zinnia. When the virus was returned to gladiolus in early stages of growth, the plants were killed. Gladiolus infected in later stages of growth, after new corms were well developed, survived to the next season. Such gladiolus, infected after flowering, apparently give rise to grassy-top symptoms when planted again. This outbreak is the only one known in which aster yellows has assumed commercial importance in the gladiolus crop.

OTHER GLADIOLUS DISEASES possibly caused by virus are mentioned briefly in gladiolus publications. They have symptoms similar to known virus diseases. Visible pathogens are lacking and proof is lacking that virus is the cause.

R. O. Magie, of the Gulf Coast Experiment Station, Bradenton, Fla., mentioned green petal stunt in the varieties Spic and Span and Golden Arrow, in which stunted petals show green veins, florets often fail to open, and plants are stunted or killed.

The disease called white pitting, known in Florida and sent to workers at Beltsville, has been found to persist from year to year in the corms. White pitting, characterized by short, stiff brittle leaves, white pitting of petals, and white or brown streaking in leaves and stems, is known only in Florida thus far.

GLADIOLUS STUNT, distinguished by plants and spikes much shorter than normal, with no mottling, streaking, or distortion, may prove to be a virus disease. Stunt is difficult to recognize until the symptoms are fully expressed. It is said to be widely distributed and responsible for much of the decline in vigor of old varieties, and, therefore, is feared more by growers than the other known or suspected virus diseases.

The gladiolus thus is known to be subject to four well-known viruses of wide host range bean yellow mosaic, cucumber mosaic, tobacco ring spot, and aster yellows viruses and to several suspected virus diseases. But we do not have all the information we should have about the agents that transmit them, their host range, and varietal reactions. Until more detailed knowledge is available there is little basis for suggesting a sound program of control.