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Ask Dr. Hort: Alternate pesticides to battle chinch bugs

Try to alternate pesticides in battle against chinch bugs

Q: My lawn is in bad shape, but I have seen no bugs. What is going on?

Steve Silverson, Seminole

A: I see a little "just sprayed" sign in the photo of your lawn. What were they spraying for? The damage looks like characteristic chinch bug! These tiny critters (1/5 of an inch) are in full swing sucking the life out of St. Augustine grass. Frequent applications of soluble nitrogen fertilizer and over-watering cause excessive thatch build-up, which in turn increases chinch bug populations, which in turn causes more frequent pesticide application, which in turn results in chinch bugs becoming more resistant to chemicals. Chinch bugs are becoming resistant to Talstar (bifenthrin), a pyrethroid, so alternate with Sevin (carbaryl), a carbamate, or Merit (imidacloprid), a neonicotinoid. This way you change the mode of action of the pesticide, resulting in more effective management, plus an overall reduction in the use of pesticides. Always apply pesticides according to label directions!

Divide African iris clumps to aid blooms

Q: I bought this plant many years ago and this year was the first time it bloomed. It is stunning but I don't recall what it is and can't find it in my gardening books. Would you be able to enlighten me?

Paula Maurer, Seminole

A: What you have is African iris, Dietes bicolor. It is in the iris family, Iridaceae, has yellow or white flowers with purple ink spots and grows as a rhizome (underground stem) forming clumps. Planted from seed it takes several years to bloom, as yours did. It is very drought-tolerant after establishment but has more blooms if irrigated. It is a good idea to divide the clumps every three to five years to continue maximum bloom. Dietes iridioides, also called African iris, has larger white flowers with yellow and violet markings.

Looking for shade and sidewalk appeal

Q: We lost a gorgeous oak tree in our front yard, and it has definitely taken away some significant curb appeal from our property. This oak tree was about 14 to 16 feet around and essentially provided shade to our entire front yard. We are 60 years old, so I don't want to wait for a tree to grow over the next 30 years! What kind of tree has some strength and will grow to some decent height relatively quickly? And, of course, provide some shade!

Vern Barclay, Lutz

A: Fast and large are scary terms when choosing a front yard specimen tree. Having said that, my first choice would be winged elm, Ulmus alata, a much-underused native deciduous shade tree with small leaves and an interesting corky, fluted bark. It attains a height of 50 feet and a spread of 30 feet. A close second is Drake elm, Ulmus parvifolia 'Drake.' Though not native, it is about the same height with a wider spread of 50 feet and a gorgeous reddish-gray bark.

A total change of thought would be grouping palms. Queen palm, Syagrus romanzoffianum; Washington palm, Washingtonia robusta; or our state tree, Sabal palmetto, could be purchased with many feet of clear trunk, giving you instant shade with three to five in a group.

Hire an arborist certified through the International Society of Arboriculture to train your new tree so it doesn't turn into a hazard halfway through its life span.

Need help?

Enter Greg "Dr. Hort" Charles, who for more than 30 years educated gardeners through the Pinellas Technical Education Centers. He answers questions about landscape and garden pests. E-mail your questions to drhort@tampabay.rr.com or to features@sptimes.com (put Dr. Hort in the subject line). Mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe your problem in full, and include your name, city and contact information. If possible, include a photo. We will print his advice on Saturdays in HomeLink.

Ask Dr. Hort: Alternate pesticides to battle chinch bugs 07/23/10 [Last modified: Thursday, July 22, 2010 6:17pm]

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