Behavior of dithiopyr in soil and its effects on establishment, growth and development of turfgrass

Abstract

Dithiopyr, a pyridine class of herbicide, is used for selective control of weeds in established cool-season and warm-season turfgrasses. It enters to the plant system through developing roots or shoots, and can be absorbed by the plants any time between germination and seedling emergence. Dithiopyr stops plant cells from dividing and elongating in the meristematic regions. Its activity is most visible at the root tips of the susceptible plants. Dithiopyr is strongly absorbed to soil colloids and has low tendency for leaching. The potential movement in runoff water is also low due to low water solubility (1.38 mg/kg) and adsorption (Kd = 3.97 to 5.78 in alluvial soil) of dithiopyr to soil colloids and turfgrass. Dithiopyr has a short to moderate persistence (4 to 49 days half lives in turfgrasses, and 11.9 to 12.9 days in alluvial soil), and is degraded primarily by soil microorganisms. Chemical degradation of dithiopyr is also common in natural systems. Other losses can occur through volatility and to a lesser extent by photodegradation (UV light). Dithiopyr may cause initial shoot injury to turfgrass in the form of thinning, yellowing of leaf tip, leaf die-back, and stunting of growth. It can reduce initial rooting of newly seeded turfgrass or installed sod of both cool-season and warm-season turfgrass species. Proper timing and rate of dithiopyr application helps in better establishment of turfgrass from seed by reducing weed competition, particularly from Digitaria species. Dithiopyr can safely be used for weed control in established turfgrass environments.