18 
Leaves of young shoot of healthy plant at left and mosaic 
plant at right. Leaves of healthy plant have a uniform flower solid pink. 
dark green color; leaves of diseased plant are light green 
and mottled. 
SYSTEMIC DISEASES—Cont. 
VIRUS MOSAIC, STREAK AND YELLOWS 
SYMPTOMS: Mosaic and streak have been present in carnation plantings for many years. Mosaic is 
very common but seldom causes extensive damage whereas streak is less common and is more in- 
jurious. Mosaic is evident as a mottling in young, actively growing leaves. When these leaves be- 
come older this pattern is no longer evident. Flower breaks that occur in King Cardinal and in some 
Fisher varieties are due to mosaic and they are severe enough occasionally to produce cull bloom. 
Mosaic can be spread either by aphids feeding on infected plants or by rubbing the sap of a 
diseased plant into the leaves of a healthy plant. The virus can be transmitted to a number of 
garden pinks by these methods also, and in some of them the mosaic symptoms are more distinct 
than in the carnation plants themselves. Sweet william can serve as a good test plant for deter- 
mining which carnations are affected with mosaic. Briefly, using the sweet william test, has failed 
to find a plant free of mosaic among a number of commercial varieties tested. Mosaic is not seed- 
borne and seedlings will remain free unless contaminated. 
Streak is marked by broken lines or streaks in the leaves. These short streaks may be white, yellow- 
ish brown, or purplish. These symptoms are plainly expressed in older leaves of established plants 
in spring, especially during March to May. Post reports (1947) that he found only slight expression 
of streak in St, Louis and Los Angeles plantings, but it was widespread in San Francisco and Denver 
greenhouses. Evidently low temperature intensifies the expression of the disease. Streak is not trans- 
missible by grafting. It does spread among plants grown out-of-doors and so some insect carrier of 
the disease is suspected, although none as yet has been found. Yellows is merely a combination of 
mosaic and streak. 
CONTROL: Since all known standard varieties of carnation have mosaic it is impossible to control this 
disease unless we start the stock from seedlings. Such is the case with the new Yoder Brother varie- 
ties. These seedlings have been kept in isolation and away from all existing named varieties plus 
the control of all aphids. 
Streak may be eliminated by careful rogueing and selection of propagating stock and by keeping 
the plants in screened greenhouses throughout the year. Some workers in Colorado believe that 
streak is no more than an expression of aster yellows which is spread only by aster leaf hoppers, 
so once a streak-free clone is established, it could be maintained in a healthy condition by screen- 
ing and occasional rogueing. 
All Photographs of Carnation Diseases in this Manual provided through 
the courtesy of the Illinois State Natural History Survey, Urbana, Illinois. 
White streaking in flower due to mosaic Natural color of 
