Effects of 2,4-Dichlorophenoxyacetic Acid on the Growth of Grass Plants

Abstract

Potted soil in which Kentucky bluegrass (Poa pratensis), redtop (Agrostis alba), and creeping red fescue grass (Festuca rubra) seeds had been planted was sprayed with water mixture containing 0.1% 2,4-D and 0.5% Carbowax 1500 at rates equiv. to 3/4, 11/2, 21/4 and 3 lbs. of the acid per acre. Treatments reduced the number of redtop seedlings that appeared by 28, 83, 83 and 95%, respectively. Fescue emergence was reduced 10 and 17%, respectively, by the 21/4- and 3-lb. rates, but no reduction occurred at the lower, 3/4- and 11/2-lb. rates. More bluegrass seedlings (14%) appeared in the 3/4 lb. per acre treatment than in unsprayed soil. Heavier applications reduced the emergence of bluegrass 32%. Weights of clippings taken at weekly intervals were less for all 3 spp. in treated soil than in untreated soil early in the expt., but each showed a tendency to recover. The grass in soil treated with 3/4 and 11/2 lbs. per acre had recovered after 5-11 weeks but at rates of 21/4 and 3 lbs. it was still retarded in growth after 14 weeks. Detrimental effects of 2,4-D in soil were only temporary, since 5 weeks after treatment redtop, fescue and bluegrass seeds germinated and grew well in treated soil. Well-established creeping bentgrass was depressed in growth by application of 2,4-D at each of the spray rates used. Plants sprayed with the acid at the 3/4-11/2 lbs. rates recovered within 3-4 months. Kentucky bluegrass, creeping red fescue and redtop turf growing out-of-doors was unchanged in appearance by water sprays at rates of 3/4, 11/2, 21/4 and 3 lbs. of acid per acre. However, the weight of clippings was reduced for 1-2 months by treatment, but later there was no reduction.