|Abstract or Summary
- HOE 23408 [ 4-(2' , 4'-dichlorophenoxy)-phenoxy-u-propionic
methylester.1 is a promising new compound for control of wild oats
and other grass weeds in small grains. Several factors influencing
its use for this purpose were investigated.
Greenhouse bioassay studies were conducted in 1975 to determine
relative persistence of HOE 23408 in four western Oregon soils
following application in the fall and winter. -Wild oats (Avena fatua L.)
were used as a test plant. Soil from each of three application
timings at all four locations contained measurable amounts of
Generally, residue levels in soil treated at the same herbicide
rate approximately 1, 2, and 4 months before sampling were similar.
Possibly less herbicide reached the soil from postemergence treatments, compensating for the longer degradation time of the preemergence
treatments. Variation in residue levels among locations
occurred. This may be explained by differences in smoothness of
seedbeds and amounts of plant residue at the various locations.
A study was conducted to determine persistence of HOE 23408
applied to bare soil on April 29, 1975. Wild oats and corn (Zea mays
L.) were used as bioassay plants. Evaluation of plants seeded into
the plots at intervals showed a gradual reduction in levels of herbicide
through the season. At 1 lb/A, neither species planted 9 weeks after
application was injured, indicating that no significant carry-over can
be expected from this rate applied in spring wheat. Two and 4 lb/A
persisted longer, causing injury to test plants seeded 9 weeks after
A field experiment was established to evaluate the effect of
combining each of four commercially used broadleaf herbicides with
1 and 2 lb/A of HOE 23408 on control of wild oats and barnyardgrass
(Echinochloa crus-galli (L.) Beauv. ) and on yield of Fielder spring
wheat. The addition of bromoxynil improved the effect of HOE 23408
on wild oats but reduced its effectiveness on barnyardgrass. Addition
of 2,4-D LV ester, MCPA LV ester, or dicamba amine reduced
its activity on both wild oats and barnyardgrass. Delaying the
application of 2,4-D for 3 or 7 days eliminated the antagonistic effect
but a delay of only 1 day was not sufficient. No detrimental effect on
yield was observed from any treatment.
A tolerance study was conducted in three commercially used
spring wheat cultivars (Waldron, Twin, and WS-1). Excellent tolerance
to HOE 23408 was observed in all cultivars, even when the
rate was increased from 1 lb/A (proposed use rate) to 4 lb/A.