Florida Agricultural Experiment Station


conditions. Consequently, work has been in progress for the
last five years to develop a resistant melon that will meet the
market requirements for Florida-grown melons.

 SUMMARY OF WORK AT LEESBURG LABORATORY
 The fact that the watermelon was one of the crops in which
disease resistance was first observed and that workers in other
states have succeeded in developing watermelon strains resist-
ant to wilt encouraged the belief that it was possible to develop
wilt-resistant watermelons suitable for Florida conditions.
 The first step in carrying out such a program was to test
under Florida conditions and in heavily wilt-infested soil as
many strains and varieties of watermelons as it was possible to
secure in the short time before the planting season of 1930.
In that year, 104 varieties and strains of watermelons, includ-
ing a few citron varieties, were tested for resistance.
 The land selected for the experimental trials had been used
for growing watermelons four different seasons during the pre-
ceding 10 or 12 years, and in 1929 only one carload of melons
was harvested from the entire 40 acres. This low yield was
attributed to wilt, but it is possible that other diseases may have
been partly responsible. It was not possible to determine the
degree of wilt infestation in the soil before the first year's trials
or to build it up through the application of highly infective
material, such as cultures of the wilt fungus or with soil known
to be heavily infested with the fungus. As a result, it was found
that the field was not uniformly infested with the organism.
In all subsequent plantings, however, one or more applications
of a handful of heavily infested soil was added to each hill.
Furthermore, all of the plants dying from the disease were
chopped into the soil. The effects of this treatment may be
seen in Figure 6, which shows the general killing in a portion
of the field during 1931.
 Fertilization and cultivation in the experimental field have
closely approximated the common practices in the Leesburg
area. The plants were counted frequently each season to check
on the amount of killing in the various strains. A final check
was made at the end of the season by cutting all surviving vines
and examining them for evidences of wilt infection.
 Each year many strains were discarded because they showed
no conspicuous resistance to the disease or other especially de-
sirable characters. On this basis almost half of the 104 strains