2010 Summer Summary - September 15, 2010
Jeff Schalau, Associate Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County

June’s cool temperatures caused warm season crops such as squash and beans to get off to a slow start. Tomatoes seemed to do well in many gardens, but Curly Top Virus (CTV) impacted some growers and home gardeners. It seems we’ve had a decent fruit growing season this year too. Thankfully, this summer’s monsoon season brought ample rains to many parts of the Verde Valley. Northern Arizona ranchers are quite pleased about this unless they happened to be passed over. Conversely, many areas had intense hail storms that would have decimated an unprotected vegetable garden. Unfortunately, hail storms and CTV are not unusual for us, but the cool weather in June was definitely out of the ordinary.

Our offices had multiple calls about aggressive honeybees. I assume that most of these occurrences were Africanized bees (it is difficult to differentiate between European and Africanized honeybees). Most recently, a horse boarding and training facility near Prescott Valley experienced two horse mortalities after honeybees became aggressive and attacked several horses. Workers at this operation were aware of honeybees nesting in the walls of a structure at the facility and allowed them to stay because they were well behaved. Perhaps an Africanized bee colony moved into a historically docile bee colony and caused it to become more aggressive. Residents should be careful around all wild honeybees and remove bee colonies from their property before they become aggressive and injure people, pets, or livestock.

A rust fungus has infected many of the native catclaw (Acacia greggii) plants throughout the Verde Valley. This rust fungus is called Ravenelia pringlei. It is noticeable where it causes a distorted growth pattern commonly called a "witches broom". The witches brooms also are covered with powdery, dark brown fungal spores which is followed by death of the infected branch. There is no known treatment for this disease. It is likely a cyclic disease acting as a natural population control on its host the Acacia. If you have it in an intensely managed area of your landscape, let it run its course over the summer and prune out the affected branches next winter discarding or burning the trimmings.

Many Leyland cypress trees (Cuprocyparis leylandii) are being colonized by another fungal disease called cypress canker. This disease, caused by the fungus Seiridium unicorne, has been called the most damaging disease on Leyland cypress. Leyland cypress trees of all sizes and ages are affected. Cankers appear as sunken, dark brown or purplish patches on the bark, often accompanied by extensive resin flow. This damage causes twig, branch and stem dieback. Spores of the fungus are spread to other parts of an infected tree, from tree to tree by water splash from rain or irrigation, and can be transmitted on pruning tools. Many people and communities have planted Leyland cypress trees over the years and this disease was first noted by me about five years ago. There is no known treatment for this disease. However, the good news is that Arizona cypress (Cupressus arizonica) trees seem to be less susceptible. I was never crazy about Leyland cypress, but now I discourage its use.

The last tidbit arose from an e-mail question: What is the name of the weed/bush that grows very quickly, several inches/feet per year, and tends to be a brighter green with a very tough root and stem structure? It blooms in the fall and releases a white cotton-like seed that blows everywhere. It is very common in the Verde Valley area over the past few years. Several readers are probably thinking that it is Desert Broom (Baccharis sarothroides). Many people believe this plant to be an invader, but it is a native. It’s true that desert broom is an opportunist and often grows in disturbed sites, but it is still a native and not too difficult to control. It is also dioecious: meaning male and female flowers are borne on separate plants.

Follow the Backyard Gardener on Twitter – use the link on the BYG website (see link below). If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or e-mail us at cottonwoodmg@yahoo.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: September 9, 2010
Content Questions/Comments: jschalau@ag.arizona.edu

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