Vol. 15—1961 - NorthEastern Weed Science Society

71.'
TABLE 3.
RESPONSE OF VEGETABLECROP SPECIES TO 8 LBIA OF
DIPHENAMiD
--------------_ .....-----------------­
I . Moderately Toleran" t Tolerant t Susceptible
-- ..._........_...... - ..... _----- ....... -----------­
I
t
Green Peppers Turnips
Cucumbers
Red Beets
&
Lima Beans Radishes I Cabbage
Spinach
Peas Mustard Carrots t
l.
Cantaloupe
....... - - ...... _'_ - - - - - - _1-
...... • ..... • _
Forage Lesumes -- Alfalfa, red clover, crimson clover, Dutch
white clover, Ladlno clover, birdsfoot trefoil, and Korean
lespedeza were the crop plant~included in three pre-emergence
field tests of diphenamid on forage legumes. Severe damage to the
clovers occurred at rates as low as 2 lb/A. Alfalfa, birdsfoot
trefoil, and Korean lespedeza were tolerant of 4 to 6 lb/A rates.
Grass weed control was good at 4 Ib/A. Pigweed and lambsquarters
were killed at 4 to 6 lb/A. Incorporation of diphenamid into the
soil did not improve activity over surface application.
Field Crops -- Two field crop experiments were conducted in
which diphenamid was applied at 2, 4, and 8 lb/A. The field crops
were alfalfa, soybeans, snapbeans, corn, sorghum, oats, sugar beets,
and cotton. Of these, alfalfa, soybeans, snapbeans, sorghum, and
cotton werp tolerant to diphenamid at rates through 8 lb/A. Good
grass weed control was obtained at 4 lb/A. Broadleaf weed control
was satisfactory at 4 to 8 lb/A in those plots in which pigweed
and smartweed were the dominant broadleaf species.
Mode of Action
Diphenamid has no activity against non-germinating seeds. It
is highly active against susceptible germinating seedlings. However,
established plants of susceptible species can be severely
damaged or killed by post-emergent application at higher levels.
In a number of turf experiments it was found that rates of 20 lb/A
of diphenamid granules completely killed turf grasses such as
bluegrass, bentgrass, and Bermuda grass.
Diphenamid is absorbed through the roots of susceptible plants
and shows little or no contact foliar activity. In instances ~re
susceptible plants have not been completely killed by the compounD,
t.he roo t sy st.em is usually severely stunt.ed.