   Spring Turf Care - April 10, 2002 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Start preparing your lawn for summer now. Cool season turf species (Kentucky bluegrass, tall fescue, fine fescue, and ryegrass) will soon go dormant and they need your help to make it through the hot summer months. During April, these cool season grasses need fertilizer, ample irrigation, and close monitoring for pests. Warm season turf species (bermudagrass and buffalograss) will soon become active and need little if any care this month. How do you know if your turf is cool or warm season? If it stays green through the winter, assuming it is under irrigation, then it is a cool season species. If it turns brown after the first hard frost and remains that way until late spring, it is a warm season species. If it is somewhere in between, it is either an unhealthy (stressed) cool season or a weedy warm season lawn. Some people also overseed bermudagrass with a cool grass such as ryegrass. This may work in Phoenix, but it is not recommended for our higher elevations. Cool season species are most active in the fall and spring. Growth slows during the colder winter months and during the hot summer months. The real attraction of the cool season grasses is their ability to remain green year-round. Of the cool season species suitable for our area, tall fescue is the toughest and most durable. Tall fescue is used for softball fields and parks. Kentucky bluegrass is a more brilliant green, but not as tough. It is often planted in combination with ryegrass and/or fine fescue. Another advantage of Kentucky bluegrass is its ability to slowly spread and fill in bare patches through tiller growth. To prepare cool season species for summer, fertilize them with ½ lb of nitrogen per 1,000 sq. ft. This would be equivalent to 2.5 lbs ammonium sulfate (21% nitrogen)/ 1,000 sq. ft. or 1.1 lb urea (46% nitrogen)/1,000 sq. ft. This rate of fertilization should occur once in early April and a month later in early May. If you are handy with math, then you can calculate the rate per 1,000 ft by multiplying 0.5 times 100 and dividing it by the percent nitrogen on the package. Warm season turf species should not be fertilized until May. Some fertilizer manufacturers will print rates on the package. This can be handy for calculating application rates. However, don't rely on the fertilizer bag to specify when to apply the fertilizer. Timing of application varies widely with climate and turf species. Remember: there is no quicker way to stress (and potentially kill) a cool season grass than to fertilize it in summer. Calculating the fertilization rate is the easy step. The real challenge comes in spreading the recommended amount of fertilizer evenly over the lawn. Drop-type spreaders are nearly impossible to achieve an even application. On these devices, the fertilizer simply falls through the bottom of a trough on wheels. Rotary spreaders "broadcast" material in a circle around the spreader. With a quality rotary spreader, distribution will be "feathered" near the outer edge of the circle. By overlapping the edge on the next pass, the concentration of material evens out and the lawn gets an even feeding. This is an art as well as a science and it takes some practice. Irrigate the turf immediately after fertilization. Check the system for damaged or broken heads. Replace/repair the heads as needed. You can also check the distribution of water by randomly placing tuna fish or cat food cans across the lawn, running the system for 15 minutes, then measuring the amount of water in each can. During April, Kentucky bluegrass should be getting between ½ to ¾ inch of water per week and tall fescue and bermudagrass should be getting about 3/8 inch of water per week. A major cool season turf pest in our area is the white grub that feed on the grass roots. These grubs are larvae of the chafer beetle. The adult insects are the small brown beetles that are attracted to lights during summer. White grubs cause the greatest amount of damage to Kentucky bluegrass. Damage appears as small dead patches. If grubs are suspected, carefully dig up the infested area and look for one-inch long, "C" shaped grubs with six legs behind the head. A similar grub, the fig beetle larva, is larger and typically feeds on decaying organic matter rather than live roots. Various control strategies are available to control white grubs. Ravens, skunks, raccoons, and coyotes will dig and feed on grubs. Commercially available parasitic nematodes (Heterorhabditis bacteriophora) can also effectively control chafers. If you see more than six grubs per square foot of turf, chemical controls may be justified. Some products that are labeled for control of white grubs in residential turfgrass are Imidacloprid (Merit), Carbaryl (Sevin), and Trichlorphon (Dylox). I would only recommend using these products if the infestation is causing significant economic damage. The University of Arizona Cooperative Extension has turf maintenance calendars for the major grass species. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://ag.arizona.edu/yavapai/anr/hort/byg/. |