There has been much discussion here in the past about how to treat turf and turf pests. Your turf can be cool season (C3) or warm season (C4) types, or a combination of the two. Pests can be weed plants, insects, diseases or other undesireable incursions like animals. To understand the proper timing and application rates of all turf chemicals, it is first necessary to understand the biology of the target species. If you do not know the life cycle of the organism you are dealing with, your program is just a wild guess. As a cool season turf manager, I will use C3 turf environment examples, but the same basic ideas, probably with different timing, will apply to C4 turf. The new account in spring will expect to see you making a lawn look good for the season. I have always told new spring clients that they will not see any improvements for a year. This is because they are asking me to come in at the end of the C3 turf life cycle, and how can I promise results if I'm starting way past the beginning. Cool season turf life cycle is Sept to mid-June in our area; summer is just a survival mode for C3 grasses. As temps cool in Sept, the plants are able to metabolize better, producing food and growing new stems and roots. This is the best time to feed your C3 turf, and that is why university researchers recommend heavy fall fertilization. This is also prime time to control weeds, so the turf fills in spots occupied by weeds. An aside on THE weeds, dandelion & crabgrass. Dandelion is a winter perennial - it germinates most heavily when temps drop (= fall), and it flowers most heavily in the spring. Since most germination is fall, it is easiest to control then (younger, actively growing); very difficult to get control in spring before flowering. Crabgrass is a summer annual - germinates as ground warms in late spring, goes to seed and dies in fall. Best control is then spring, by interrupting germination with pre-ems, or using post-ems quickly on juvenile plants. While most consider C3 grasses to be dormant by Thanksgiving, in reality they do not stop growth until the ground freezes. They are continuing underground development to grow well next spring and survive next summer. Bluegrass rhizomes really start to grow in Nov, and I have seen some grow over a foot, up to 18 inches, in mild winters. Also C3 turf stores energy in roots for spring growth. A good late season fert app will provide food for this growth & storage, and if we get a good freeze, the fert is frozen there for use in early spring; no need to guess when to make a spring app. In the spring C3 turf is in late middle age. Stored energy and residual nutrients in soil will be used to grow well and reproduce (go to seed). My basic plan is to not fertilize our turf until after bluegrass goes to seed - NO FERTILIZER UNTIL MEMORIAL DAY. Research has shown that spring fert apps just enhance leaf growth and seedhead production; there is no benefit to the real health of the plants. Spring mowing in C3 turf is hard enough, why add to the leaf growth? Early spring C3 turf fertilization is just a knee-jerk attempt to "have a really nice lawn this year", or a fertilizer or lawn care salesman's attempt to churn $$$$ right away. A good fert after turf goes to seed will help the plants to produce food and grow roots to survive heat (and drought) of summer. In hotter temps, C3 grasses are very inefficient in making their food, and can in fact die from extended heat because it runs out of food, even when there is plenty of nutrient in the soil. Anyone ever had raccoon damages on lawn? Raccoons instinctively know that there is food in the ground, but it is hard work to get it. (Exception is grubs. These are a delicacy to many animals, and even to some human cultures.) So digging for food is the last choice for the raccoon. You will generally see raccoon damage to turf starting in mid summer (when there are no grubs in soil). This occurs because that is when young are starting to forage on their own, and they haven't found easier ways. (Yeah, they know the grabage cans, momma showed them, but other coons own that territory.) So, if you're seeing a lot of coon roadkill in early summer, population is high this year, youngsters are gonna be rooting in lawns soon, and might be good to keep a couple of traps on the truck ready for setting. Same understanding of life cycles of turf pests like grubs, dollar spot, and anything else will help you to do your job correctly. You can read the label 50 times, but if you don't know life cycle of your target, your application can be as effective as a fart in the wind. Know the general life cycles, and observe the specific activity of the plants or pests in your area, in order to design your own program to get the results you want.