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John Fulton


John Fulton
Former County Extension Director



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In The Backyard

Horticulture columns and tips done on a timely basis
crabgrass

Lawn Care as we approach August

Posted by John Fulton -

Crabgrass and other annuals grass weeds can be seen about everywhere. Annual grasses which are common include the different crabgrasses, foxtails, and barnyard grass. They have been the most asked about items this past week. They will die with the first frost, so treatment is not available, or recommended, in the fall. The only exception to available treatments is the use of glyphosate (Roundup is one trade name) in areas where there are no desirable plants. Make a note of where these grasses are, and an overseeding to thicken up the grasses you want there may help crowd out the annuals. Preventative treatments may also be applied in the spring (around April 1 depending on soil temperatures) to kill the germinating seeds. As many have found out, a second treatment about June 1 is also necessary since the products only last six to eight weeks. The short life of preemergence treatments actually gets shorter in extremely wet years. These grasses are extremely troublesome this time of year as they stay wet and tend to clump on the bottom of mower decks, but there isn't a cure at this time – other than the continued mowing.

Keep mowing when the grass or weeds dictate mowing. The rule of thumb is to remove no more than a third of the leaf blade at any one time. This means that if your desired mowing height is 2 inches, you should be mowing when the grass gets 3 inches tall. No summer slump this year, due to all the rain. We have been on the program of mowing every three days since we began in the spring. It's amazing what rain will do.

With relatively few adult beetles to lay eggs, which then hatch into grubs, there will probably be very light grub pressure over all. This would be especially true considering the excellent growing conditions for grass this year. Grub problems are normally found first along walks, driveways, or patios. The insecticide must get to where the grubs are, so make sure to water the liquid formulations in as soon as they are applied. The two widely available products are GrubX (halofenozide) and Merit (imidacloprid). Remember the active grubs now are from the June bug, and we'll want to wait another two to three weeks on trying to apply grub treatments for the Japanese beetle grub. Carbaryl (Sevin) granules are an option for Japanese beetle grubs, but they don't work on the other species.

Yellow grass tops are visible in many areas. This tends to happen in very wet years when nitrogen is taken from the root area, and trees and shrubs grab available nutrients. There is also a lack of oxygen in the soil due to all the small pore spaces being filled with water in years such as this one, where heavy rains have been frequent. In the past, treatments haven't had much effect in the current growing season. Next year you won't see the same problem, at least to start the season.

Fall seeding of grass should be done between August 15 and September 10. This is a tried and true date, but the end of the world won't come about if you are a week later. The goal is to give the seed enough time to germinate and become established before bad weather arrives. Seed at the rate of 4 pounds of seed per 1000 square feet on bare spots, or half that rate on overseedings.

If you have a compacted yard, or have a deep thatch layer, these seeding dates also define ideal times to dethatch or aerate. Thatch layers should not be over 1/2 inch deep for optimum growing conditions. When aerating, make sure you use a core type aerator.

 



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