Pre-Emergence Herbicides for Crabgrass Control and Their Effects on Germination of Turfgrass Species

Abstract

fURING the past several years, pre-emergence herbicides for crabDi grass control in turf have come into prominence. Some herbicides are relatively new; others, such as lead arsenate, calcium arsenate, and chlordane, have been used as herbicides for a number of years. Research workers have included the old as well as the newer herbicides in experiments under controlled conditions to determine their effectiveness as pre-emergence herbicides. However, information on the effect of these herbicides on the germination and growth of turfgrass species is limited. Application of leaa arsenate as orchard sprays over the years had a toxic effect on the soil after the orchards had been removed and the areas planted to other crops due to arsenic accumulation. The poor condition of young alfalfa and barley in the affected fields was roughly proportional to the concentration of readily soluble arsenic in the surface soil (3). Arsenic uptake by some grass plants may be injurious according to Daniel (1). In his studies, injury to Poa annua L. (annual bluegrass) was still evident 3 years after an application of 30 pounds of lead arsenate per 1,000 square feet when the phosphorus supply of the soil was low. Soils high in phosphorus required a higher arsenic accumulation before growth of annual bluegrass was inhibited. Fuchigami and Youngner (2) found that products containing approximately 5 percent water soluble arsenic were highly toxic to clover and discolored turfgrasses. There are many variables which influence the toxic effect of pre-emergence herbicides, among which may be listed pH, organic matter, phosphorus and potassium levels, thatch, and soil type. The study reported herein was designed to provide information on the following questions: 1. How long before crabgrass germinates can pre-emergence herbicides be applied and give effective control? 2. How soon can turfgrass species safely be seeded after applications of pre-emergence herbicides? 3. What is the relative susceptibility of turfgrass species to injury by pre-emergence herbicides?