Watermelon Plant Diseases and Their Control 
WILT—Entire plant wilts (at first only during 
hot part of day), and finally dies. Water vessels 
in wilted stems appear discolored. 
PREVENTIVE—Plant on new land whenever pos- 
sible. At least do not plant on same land oftener 
than once in 4 or 5 years. Gather and burn old 
vines after harvest. Plant resistant varieties such 
as Hawksbury No. 8, Blacklee No. 45, Wilt Proof 
Kleckley Sweet No. 6, Variety No. 19, Missouri 
Queen No. 52, Miles Melon No. 54 and the New 
Melon Ironsides No. 56. 
ANTHRACNOSE—Black spots on leaves and 
stems. Young fruit becomes dark colored and 
shrivels when the stem is attacked. Spots on 
sue are numerous, large and often of pinkish 
color. 
LEAF SPOT—Small, round, black spots on older 
leaves near base of stem. These leaves die and 
drop off. 
DOWNY MILDEW-—Irregular black areas on 
leaves. Under moist weather conditions the entire 
foliage may be killed. Sometimes a faint, purplish, 
downy growth may be seen on the under side 
of the infected spots. 
TREAT ALL THE ABOVE DISEASES AS FOL- 
LOWS: 
A combination of crop rotation, destruction of 
plant refuse, seed treatment and spraying or 
dusting are necessary to keep in check these 
diseases of watermelon. 
PARZATE controls Downy Mildew, Leaf Spot, 
Anthracnose and Leaf Molds. 
PARZATE is a powerful fungicide and yet it is 
mild on plant leaves, so mild in fact that it will not 
burn or stunt even the most sensitive plants. It 
comes in liquid or dry form, is a Du Pont product. 
See your local dealer; if he does not have it write 
Du Pont, Grasselli Chemicals Dept., Wilmington, 
Delaware. 
BLOSSOM-END ROT—Discoloration and shrivel- 
ing of the blossom end of melon. Decay progresses 
inwards. No control methods are known, although 
the affected melons should be removed from the 
field to prevent the development of parasitic organ- 
isms on them which may possibly infect other 
fruits and portions of the vine. 
COLD, WIND and SAND INJURY 
When young plants are exposed to very low 
temperatures, which do not kill but cause severe 
damage by stunting to such an extent further 
growth is slow. Growth is almost entirely stopped, 
and when further growth occurs it is often in an 
irregular manner, causing curling of the leaves 
making them more susceptible to attacks of various 
44 WILLHITE MELON SEED FARMS, Poolville, Texas 
fungi than those in a more normal condition of 
growth, and are often killed by such fungi. 
Strong winds, in March, often whip and tear 
the leaves severely, drying them out and the torn 
edges become hard and brittle again making them 
susceptible to the attacks of fungi. The most 
serious type of wind injury, however, occurs dur- 
ing fruit setting by whipping off blossoms and in- 
juring young melons until they turn dark and drop 
off. 
BLOSSOMS BUT NO MELONS 
The setting of melons is dependent on pollina- 
tion by insects, usually bees or the striped cucum- 
ber beetle, however, temperature and moisture 
conditions must also be right for satisfactory pol- 
lination. High temperatures and extreme dry 
weather prevailing through much of the growing 
period may result in poor set of melons, even 
where plants are grown under irrigation high tem- 
peratures might interfere with pollination. “With 
most plants the proper pollination of blossoms is 
dependent on a set of conditions, all of which must 
be just right at blossoming time.” All cucurbits, 
which include melons, squashes, pumpkins and 
cucumbers, produce separate male and female 
blossoms, with the former which carry the pollen 
predominating over the female or fruit-forming 
blossoms by ten or more to one. A large number 
of blossoms, therefore, does not necessarily mean 
a heavy set of fruit. Generally, during the grow- 
ing season, periods occur when all necessary con- 
ditions are right and a normal crop of melons is 
produced. 
ROOT KNOT—Elongated swellings or small, 
round galls on the roots of plants are common 
symptoms of the root-knot disease. The causal 
agent is a small worm, called a nematode, which 
is scarcely visible to the unaided eye. Plants 
affected with rootknot are lacking in vigor, 
stunted, and pale in color. Root-knot galls are 
ordinarily much smaller and more numerous than 
the large, more spherical swellings of crown gall. 
One might confuse root-knots with the nodules on 
leguminous plants which are produced by the 
beneficial nitrogen-fixing bacteria. These nodules 
are easily broken off from the side of the root, 
whereas nematode galls are swellings of the 
root itself and cannot be separated from the 
root. Another eel-worm, the meadow nematode, 
injures some plants by causing tufts or rootlets 
without causing galls. The eradication, or even 
satisfactory control, of root-knot nematodes is not 
easily obtained. Fields infested with root-knot 
nematodes should be planted with grasses, 
cereals, or CROTALARIA spectabilis for several 
years. At the same time, all weeds should be 
controlled since many of them are hosts for the 
nematodes. Clean fallow of the soil with frequent 
cultivation during dry weather tends to reduce the 
nematode population through drying of the soil 
and starvation. 
Weatherford, Texas 
