(This Old House) -- Unless you're a perfect caretaker of your lawn (and, really, who is?), prepare for another round in the turf wars this summer. You'll have to deal with a full frontal assault from the dandelions, of course. And an attack from the crabgrass. But you'll face more stealthy opponents, too: root-chomping grubs and microscopic mildew that turn the grass from green to gray or brown.



"If a lawn is neglected, or cared for in a hit-or-miss way, it gets weak," says This Old House landscape contractor Roger Cook. "And that's when weeds, insects, or fungal diseases become a major problem." Little wonder that last year almost 50 million homeowners bought products to fight these invaders.



But as in most battles, the best defense is a strong offense: doing everything right to cultivate healthy turf. That means giving it up to an inch and a half of water per week; aerating and dethatching annually so water and nutrients can get down to the roots; mowing with a sharp blade to the right height (ask your local garden center what's best where you live); and fertilizing in spring and fall.



So promise yourself -- and your turf -- you'll do that this year. In the meantime, here's how to conquer the most common turf problems you're likely to confront this summer.



Fungal disease



Symptoms: Circular patches of yellow-to-brown grass; or blades with tiny red threads.



Culprits: Powdery mildew, brown patch, dollar spot, and fusarium patch; or red thread. These fungal diseases can take hold of stressed turf.



Solutions: Though lawns will generally recover from small areas of infection, if a fungus is progressively marching across your yard, look for a fungicide with the active ingredient thiophanate-methyl and follow the directions. For an organic fix, search out a corn-gluten mix that will cure brown patch and weaken most other fungi. Then nurse your lawn back to health by practicing good lawn-care habits: Avoid excessive shade (prune back trees and large shrubs, if necessary) and too many applications of fertilizer, herbicides, or pesticides. Carefully monitor your turf's moisture intake and never water in the evening.



Weeds



Symptoms: Fast-growing and unruly greenery that quickly overtakes surrounding grass. This Old House: What type of grass is right for your yard



Culprits: Crabgrass or broadleaf weeds such as dandelion, purslane, henbit, and chickweed that commonly pop up where soil is compacted and grass hasn't completely taken root. To check for compacted soil, stick a screwdriver into the ground; it should slide in easily.



Solutions: The first step is to eradicate any foreign invaders. The best approach is to pull them out by hand using a weeder or a hoe. This will also loosen the soil in affected areas. Or use a liquid herbicide in a hand sprayer to spot-treat an infestation. If weeds are too plentiful to be pulled, check your garden center for a "weed-and-feed" blend of granular fertilizer and herbicide that will kill weeds without harming turf types commonly grown in your area, or look for an organic fertilizer with corn gluten. Be sure to follow the directions on the box exactly, as some formulas must be applied during a dry spell or need a 24-hour breather with no foot traffic.



From here on out, mow up to twice a week during the beginning of summer when grass grows swiftly, and raise the mower blade an inch during hot or dry periods. Water well as the summer heats up, and your turf should naturally overtake the weeds. In the fall, open up compacted soil poke holes with a pitchfork over a small yard, or rent a power aerator for large yards and overseed the lawn. You may want to follow up with a pre-emergent herbicide next spring.



Insects



Symptoms: Brown turf that becomes loose enough to lift like a mat.



Culprits: White grubs, a catch-all name for root-chomping
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