BULLETIN 1288, U. S. DEPARTMENT OF AGRICULTURE 
Virginia, and the adjoining 
same temperature belt. 
coast States than in inland parts of the 
NATURAL METHODS OF OVERWINTERING 
The tomato leaf-spot fungus (Septoria lycopersici) lives over win- 
ter on dead tomato vines and leaves lying on the surface of the 
ground. During the fall and spring it multiplies in the epidermal 
and subepidermal tissues of these stems and leaves and in summer 
produces numerous fruiting bodies (pycnidia) and spores. The fresh 
spores are carried by insects and other agents to young tomato plants, 
which become infected and serve as starting points for the seasonal 
distribution of the disease. 
As the tomato leaf-spot fungus infects a number of other hosts, 
it is doubtless capable of living over winter on them in much the 
same way as on tomato vines. Aside from the tomato its most 
common hosts in the 
Middle Atlantic and 
Middle Western 
States are probably 
horsenettle (Solarium 
carolineme) and jim- 
sonweed (Datura stra- 
monium). It not only 
infects these hosts 
readily but produces 
spores on them. Da- 
tura tatula was listed 
as a host of this fun- 
gus by Xorton (5) but 
the writers have found 
that it infects D. stra- 
monium quite as read- 
ily. Since Safford (13, 
lJf) has shown that D. 
tatula is in reality only 
a form of D. stramo- 
nium instead of a distinct species, this is not surprising. D. 
tatula differs from D. stramonium by having purple stems and violet 
flowers instead of green stems ancl white flowers. Safford found 
that both violet and white flowered forms come from seed of the 
same D. tatula plant, and the writers have since obtained similar 
results. 
Fig. 1. — Sun scald of tomato fruit, 
found on the side of the fruit facin 
plants are defoliated by leaf-spot 
This commonly is 
the sun after the 
POSSIBILITIES OF OVERWINTERING ON DEAD WEEDS, GRASSES, 
AND REMAINS OF VARIOUS CROPS 
There is a paucity of information on the growth and overwintering 
of parasitic fungi on dead material other than that of the host. 
Much stress is often laid on the destruction of living wild host plants, 
but little attention is given to the possibility that the parasites may 
live and multiply on dead organic matter of various kinds. Many 
dead weeds and pieces of crop plants frequently lie on the surface of 
the ground where they are not subject to the chemical effects of the 
