Cypress growth points to borer damage


Q: Because of the wind the other night, the tops of two Italian cypress trees broke off about 11 feet from the ground. We have 18 of these trees by the back fence. We planted them in 2005 and have been watering them for nine minutes, three times a day, six days a week in summer. As they grew I didn’t increase the water until about three years ago when I found out they needed more water. So now, I use a hose and water each one about 15 minutes every three weeks in summer. I’m hoping you can see by the picture, there seems to be growth around the area where it broke off. Do you think this was caused by lack of water?

A: I can see the picture quite well, thank you. I don’t need to know the watering schedule or amounts. Other people have told me that they think they had borers in Italian cypress. I had never seen borer damage in Italian cypress in my 30 years in Las Vegas.

Well, I think you have it. I think this growth you are pointing out in the picture what we typically see after borer damage has occurred. Borers don’t typically kill a plant overnight, or even in one season, unless the plant is very young and the damage is extensive. Usually plant decline from borer damage can take several years. Plants can survive and look like nothing is wrong for several years during annual borer attacks.

Having borer damage depends on a lot of things: How healthy the plant is, how fast it begins recovery after the attack, how heavily it was attacked, etc.

In short, it is possible that your plants were more susceptible to borer attacks because of a lack of water during the summer.

There is a product for borer control but it would have to be applied once, annually, to protect the trees. It is a good product and you can find it at your local nursery.

In the meantime, if the disproportionate sizes bother you, I would go ahead and lower them all so they are the same height. They should do just fine if they all are pruned the same way; I don’t think it will be very noticeable after a season of growth.

Q: We have a weed problem in our back lawn and I think it is called spurge. The leaves are small and it’s kind of viney. When I pull it, I see this white sap coming from the broken vines. I can dig it out of the soil where I have gazanias but cannot do the lawn that way. Any advice would be welcome.

A: Yes, that does sound like spurge. Spurge is a poor competitor with other plants. It invades open spots whether you are growing gazanias or a lawn. In open areas surrounding gazanias, the best option you have is to use surface mulch. Mulches can be rock or wood. Gazanias will tolerate both so pick either one.

Actually your lawn is acting like living mulch. As long as you keep your lawn a solid covering and healthy, it will be difficult for any weed to invade. Make sure your mowing height is high enough to shade the soil surface. Weed seeds like to see light if they are to germinate and invade.

Secondly, fertilize your lawn regularly to maintain its density. Fertilizers that help to maintain its leaf density and shading of the soil will be high in nitrogen.

Thirdly, make sure your sprinkler system covers the entire lawn with water as evenly as possible. Most homeowners do not understand how to design a good sprinkler irrigation system. If you are going to design it yourself, make sure you learn how to do it correctly and don’t just assume you know what you’re doing. Any weakness in the irrigation system will

result in brown patches, dead spots in the lawn, and invasion by weeds.

Make sure your sprinklers pop up high enough so they throw water from above the top of the grass.

Do not use 2-inch pop-ups unless you have Bermuda grass. Do not trim around your 2-inch pop-ups because they are too low or you definitely will see weed invasion in the lawn.

Q: I bought a bougainvillea (Barbara Karst) last April and planted it in my front yard. After digging the hole, I added a local rose and flower food in the bottom of the hole. I then added water and then planted the bougainvillea.

This plant receives sunlight more than six hours every day and I water it as noted on the label. All went well until something started to carve big divots out of the leaves. I sprayed Ortho Bug B Gone as I was told and only sprayed it on the plant at night so it would not burn the leaves.

Well it did the trick but the edges of the plant started to turn brown and shrivel up. As soon as new fresh, unsprayed tender leaves came out, the bug came back and started to carve out holes in the leaves again. Is there something I am doing wrong?

A. This is the leafcutter bee and the female is using your bougainvillea leaves to build its nests. These bugs are good guys and help to pollinate our fruits and vegetables. By the way, these bees are very docile, only sting if they are provoked and cannot become Africanized.

I never recommend spraying to control bees of any kind. I tell people to live with them and encourage watering and fertilizing to encourage more growth.

Add more plants to lessen the damage on individual plants or plant other plants to lessen the visual damage. These include roses, many kinds of flowers, grapes and basil.

The damage will not hurt your plant if you can live with it. I put more information and pictures on my blog several months ago. In the blog search engine, type in leafcutter bee.

The University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas will have its annual bare-root fruit and nut tree sale for January 2014 delivery in the next couple of weeks. The fruit trees will all be proven varieties that have done well here in Las Vegas during the past 18 years. Watch for an announcement in an upcoming article or on my blog.

The University of Nevada, Las Vegas needs your help on a water conservation study. We need 50 people who are willing to participate with their landscapes and possibly save as much as 50 percent on their water use. The study will be carefully monitored; I will be helping by visiting each site on a regular basis. If you are interested, contact me at extremehort@aol.com.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.