Tech Notes Issue 2

Nutgrass is obvious at this time

Nutgrass (puarple nutsedge) is in the family Cyperaceae (Sedge family) and is  identifiable by its triangular shaped stem, purple colouring in the top few layers of leaves, and its flowering heads are a darker red/purplish colour help identify it from other Cyperus spp. Nutgrass grows well in every soil type, over a wide range of soil moisture, pH and elevation. It can survive the highest temperatures encountered in any turfgrass system. However, it does not tolerate shaded areas.

Culturally, there are really no effective means of controlling nutgrass. Frequent and close mowing can help reduce the competitive nature of nutgrass. Handpicking of nutgrass is not very effective because the tubers remain in the soil. Herbicide treatments are the most effective, but often require repeated applications.

Couchgrass Scale: An affliction that looks like drought stress

Unfortunately there are several turf maladies that produce symptoms similar to drought stress. One of those maladies that is often misdiagnosed is couchgrass scale (Odonaspis ruthae Kotinsky). Couchgrass scale causes the warm season turf to grow slowly and begin to turn yellow during the summer. Symptoms are similar to drought stress. Heavy infestations may dramatically thin and kill couchgrass in a patch-like pattern. This type of damage is more evident during periods of hot, dry weather.

There are four stages in the life cycle of the couchgrass scale termed egg, crawler, settled nymph, and adult. The nymph and adult are the damaging stage. Crawlers begin to settle producing an oval, waxy test (shell) which is first straw yellow and then covered with white waxy secretions (settled nymph). Adult females have shells, or tests, which are egg-shaped or oval in outline and 1.0-1.75mm long. The male shells or tests are smaller. Populations can be so large at stolon nodes and crowns that the scales seem to be stacked on top of each other.

Couchgrass that is well fertilized and watered can generally outgrow this pest.  However, damage can begin to appear if irrigation must be discontinued in the summer. No insecticide is labeled specifically for this pest.