/ ,o HUME LIBRARY
1- APR 7 1971
AGRICULTURAL RESEARCH CENTER, MONTICELLO
Monticello, Florida I.F.A.S. Univ. of Florida
Mimeo Report 71-5 6 fR February 8, 1971
CONTROL OF PECAN SCAB WITH DUTER AND BENLATE:
A RATE AND SCHEDULE EVALUATION
William J. French1
An effective scab control program can be one of the most expensive items
in the pecan growers operation. Under the present control recommendations
scab susceptible varieties require from 7-9 applications of fungicide and in-
secticide per season, not to mention occasional unscheduled applications of
insecticides in emergency situations. Obviously, any program which would re-
duce the number of applications required without sacrificing nut quality or
yield would reduce the cost of production. This study was designed to evaluate
the effect of fungicide rates and frequency of applications on scab control
based on scab index, and nut quality as based on % kernel weight.
The efficacy of Duter 46.5W and Benlate 50 for scab control was compared
at .08 lb. and 0.16 lb. per tree in the standard 3 week schedule and in 4 and
5 week schedules. Sprays were applied to 35 year-old Mahan pecan trees with an
airblast sprayer circling each tree. Approximately 12 gallons were applied
per tree. Treatments were applied to single tree plots replicated 6 times.
All treatments started with the prepollination application April 8. Scab
ratings were made in September and kernel percent at harvest. Rainfall from
April 1 to September 30 was 31.14 inches, and scab pressure was high.
The results of the 1970 rate-schedule evaluations are presented in Table
1. The low rate of Benlate applied at 4-week intervals gave good control and
was comparable to high and low rates of Duter applied at 3-week intervals and
superior to all other 4- and 5-week treatments. Nuts from the high rate 5-week
treatments had higher scab indices than the standard but kernel weights were
not significantly reduced. Nut yields varied greatly within treatments due to
limb breakage which occurred throughout the growing season.
Asst. Ptait Pathologist
Results of 1970 Fungicide Rate-Schedule Evaluation.
lb. per tree
% Nuts in
Class 1 & 2
1Scab index % of shuck area scabbed 1 scab free, 2 = 1 25%, 3 = 26 50%,
4 = 51 75%, 5 = 76-- 100%.
2Benlate is not registered by the U.S.D.A. for use on pecan and cannot be
recommended at this time.
We wish to acknowledge the Monticello Nursery Company, DuPont Chemical Corp-
oration, and the Thompson-Hayward Chemical Company for their cooperation in
I --~c- r
200 cc 2/8/71