Grassy weeds may reduce cool-season turfgrass establishment after seeding and herbicide use is often warranted. Field experiments were conducted to evaluate the tolerance of creeping bentgrass (Agrostis stolonifera L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) to fenoxaprop and metamifop applications at 1, 2, 3, or 4 weeks after seeding (WAS). Creeping bentgrass groundcover was reduced from 34% to 71% at 8 WAS from the nontreated by fenoxaprop at 50 g a.i./ha and metamifop at 400 and 800 g a.i./ha at all application timings. Metamifop at 200 g·ha−1 reduced creeping bentgrass cover 10% to 18% from the nontreated at 8 WAS when applied 1, 2, or 3 WAS, but treatments at 4 WAS did not reduce cover. Perennial ryegrass treated with fenoxaprop and metamifop at 800 g·ha−1 at 1 WAS had cover reduced from the nontreated on two and one dates, respectively, whereas tall fescue cover was never reduced greater than 5% from the nontreated. Results suggest applications to creeping bentgrass should be delayed greater than 4 WAS for fenoxaprop at 50 g·ha−1, greater than 4 WAS for metamifop at 400 and 800 g·ha−1, and 3 WAS for metamifop at 200 g·ha−1. Additionally, fenoxaprop applications should be delayed 2 WAS for perennial ryegrass and tall fescue, whereas metamifop could be safely applied at all rates at 1 WAS.
Diego Gómez de Barreda, Jialin Yu and Patrick E. McCullough
Verónica De Luca, Diego Gómez de Barreda, Antonio Lidón and Cristina Lull
Due to restrictions on pesticide and nitrogen use in high-input European agricultural systems, many of the biostimulants used in horticulture are being incorporated into turfgrass management programs—although often with little understanding. A set of experiments was carried out on perennial ryegrass (Lolium perenne) cultivated in pots in a greenhouse in 2013 and 2014 to test the effect of three biostimulants: two composed of nitrifying bacteria (B1 and B2), and the other a mixture of amino acids, polysaccharides, nitrogen, and micronutrients (B3). Apart from the biostimulant treatment, nutritional stress was incorporated into the study to demonstrate if biostimulants could temporarily replace the fertilization role and so lessen the environmental impact. Turfgrass treated with B1 resulted in an increase in quality compared with untreated turf, and the positive effect lasted 2 and 3 months in 2013 and 2014, respectively. Additionally, an extended benefit was observed when the B1 interval application was longer, even temporarily replacing fertilization when applied on stressed turfgrass. The B2 produced similar results to B1, the effect was longer, and the turf exhibited a darker color—although it caused phytotoxicity at the tip of the leaves. The B3 led to a beneficial effect on turfgrass, especially under nutritional stress; it showed a better quality, darker green color, and more growth and yield than untreated turf (despite adding less nitrogen than during either mineral fertilizer treatment). Overall results show that the tested biostimulants increase turfgrass quality even when inducing a nutritional stress.