Plantation Field Laboratory Mimeo Report 59-1
SUGGESTED MEASURES FOR CONTROLLING THE ROOT ROT COMPLEX
AND LATE BLIGHT DISEASE ON PEPPERS
W. D. Moore* and R. E. Stall**
Root Rot Complex
Root rots, caused by Rhizoctonia solani and Pythium spp., have annually
caused many losses to peppers raised on the sandy soils oT he lower east
coast of Florida. This root rot complex has long been one of the most diffi-
cult diseases to control. However, a combination of practices has been success-
ful in reducing the losses. It is fortunate that these practices are usually
ones that are needed to produce a vigorously growing crop year after year even
if root rots are not a problem.
The following measures comprise the best information available on control
of pepper root rots at the present time:
1. All cover crops should be allowed to dry completely before plowing
under. In all cases plow under cover as far ahead of planting as possible,
preferably six to eight weeks.
2. Level land so that there are no low areas that become too wet. A
uniform soil moisture content is important.
3. Be sure that all ditches and canals are free of weeds and grass that
may impede the flow of water. Make certain that pumps are adequate for pumping
off excess water in a short time.
4. The best chemical combination found so far is a 50-50 mixture of
Captan and PCNB. This mixture should be applied at the rate of eight pounds
per acre. Apply as a very low pressure (20 30 Ibs.) spray or drench over
the furrow immediately following seeding. Do not cover whole plant bed. If
heavy rains fall before seeds germinate, make second application similar to
first. Disease prevention must come during and immediately after seed germi-
nation. Little can be done after the plants are 3-4 inches high.
Formerly Plant Pathologist, Plantation Field Laboratory, and cooperative
with Crops Research Division, ARS,USDA.
** Assistant Plant Pathologist, Indian River Field Laboratory, Fort Pierce,
July 30, 1958
5. The value of soil fumigants for pepper root rot control has not been
proven by experiments thus far. Those wishing to try them should do so on a
small scale at first.
Any one of the above measures will not insure a disease free crop.
best results will be obtained by using all of these procedures.
Late blight, caused by Pytophthora capeici, occurs during warm moist
weather. The causal organism, which inhabits the soil, causes a wilting of
the plants following a girdling of the stem at the soil line as well as a
blight on the stems, leaves and fruits. These two stages of the disease may
require different control procedures.
The wilting stage usually starts in low poorly drained areas. In these
areas the organism builds up and then spreads to foliage on higher ground.
Leveling the land as well as possible and providing for rapid drainage will
in most cases be adequate to control the wilting stage.
The blight stage can occur in all portions of the field during warm moist
conditions. Spraying regularly with effective fungicides will control the
blight stage even under very severe weather conditions.
For late blight control the following are suggested:
1. Level land and provide for rapid drainage in periods of prolonged
2. Spray every five days with two pounds of metallic copper per 100
gallons of water beginning when the first true leaves form. (Add 100 ppm
streptomycin during periods favorable for bacterial spot.) If rainfall be-
comes heavy and prolonged, spray with maneb (1 lbs. per 100 gals.) or
Zineb (2 lbs. per 100 gals.) between copper sprays. Do not mix copper with
maneb or zineb. When weather clears, continue using copper only in sprays
every fifth day.