Mesquite

Q: I live in the Rita Ranch area, and someone planted a mesquite in my front yard about 15 feet away from the house? Is that too close to my home? Will the roots of the tree get into my water or sewage pipes?

A: Fifteen feet is probably far enough away from your home to avoid any problems with roots invading your plumbing. One way to keep the roots of the tree from spreading out to find new water sources is to be sure to water frequently and deeply. If you do that, you probably won’t have any problems.

If you’re worried about the location of a tree, you can also have a tree or landscape company install a root barrier between your tree and the hardscape elements or plumbing that you want to protect. Then, as the tree grows and its roots spread out, they will be deflected away from your sidewalk, fence or building. These barriers can be installed when you plant a tree or even afterward.

Tree companies tell us that tree roots don’t really “look” for plumbing lines underground; what they do is exploit existing leaks. Roots in the soil keep growing and if they detect a water source, like moisture from leak, they then follow it to the break in the pipe and breach it. Then you can have plumbing problems due to roots inside pipes.

For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert for 25 years, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program, heard locally from 8-11 a.m. on KNST-AM (790) in Tucson and KGVY-AM (1080) and -FM (100.7) in Green Valley. Call 888-767-4348.

I found these seedpods on a landscape tree and need info on what type of tree this is and how does the seedpod behave? For example, does the seedpod explode or open up? There are approximately 21-25 closed spiral pods per stem. I am making jewelry out of them and need this information.

A.: Those are fruits of the screwbean mesquite tree (Prosopis pubescens Benth). The tree is native to the Sonoran Desert, as are the honey mesquite and the velvet mesquite. The seedpods look like a tightly wound spring or a screw, hence the common name. Animals that ingest them may disperse the seeds or the seeds may lie dormant in the environment for years in their protective coat. The pods don’t explode or open up and may be well suited for your purpose. Also, these are tasty and have been a traditional food in the Southwest for many years. You can usually find the flour milled from the beans at local stores. If you harvest your own pods you might be interested in the milling events provided by local nonprofit organizations.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to

tucsongardensage@gmail.com

Yesterday evening we noticed a large number of giant mesquite beetles in a couple of branches on the seedpods obviously mating. 1. Will the females disperse to lay their eggs on other food sources? 2. Will my tree lizards eat most of the young? 3. Why the large number in one place? I consider myself quite observant and have not seen these before.

A: These insects are actually called giant mesquite bugs (Thasus neocalifornicus) and differ from beetles in that they have piercing-sucking mouthparts and front wings that overlap, among other characteristics. They are fairly common in the foothills of Tucson but not always in the same places. They are not numerous every year it seems but someone always sees them and asks about them. They are only found on mesquite trees so your other plants are safe. Since they are sap feeders and not usually found in large numbers, even the mesquite trees are safe. The young are in danger from predators but because of their warning colors (red and yellow) they have some protection. Some of them will always survive.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to

tucsongardensage@gmail.com

Q: I just moved to the Tucson area and in the front yard is a very large mesquite tree that has not been trimmed much over the years.

It appears that a couple large branches may have broken in the past and subsequently the branches were cut off with a saw. They are leaking a blackish tar substance on the ground that made me think its slime flux. However there is no odor to it.

Any thoughts what this might be and if anything can be done to stop it from leaking? Otherwise the tree looks healthy.

A: You are correct. Wetwood or slime flux is caused by the infection of sapwood by several types of bacteria and is a problem with mature mesquites.

The disease-causing microorganisms are found in the soil and probably gain entry through above or below the soil line wounds or pruning cuts. After several years, affected areas will exhibit a water-soaked appearance (wetwood). Although some wounds produce no odor, the wound may produce gas resulting from the bacteria (and possibly yeasts) that force out a foul smelling liquid from cracks and wounds. The liquid is dark brown to black in color. Infected trees live many years and slime flux is more of a nuisance that requires periodically a strong, hard stream of water to prevent staining of patios and cars. There is no cure for this disease. Seriously infected branches may need removal if they present a safety hazard. The old remedy of placing drainage tubes into the infected areas is not recommended and may in fact, present more entry sites for the disease.

Peter L. Warren is the urban horticulture agent for the University of Arizona Pima County Cooperative Extension. Send questions to plwarren@cals.arizona.edu

Q: I got a half cord of mesquite firewood last fall. Now I am seeing a lot of holes and sawdust around the woodpile. The wood is outside away from the house, but I am wondering if these insects will attack live trees in my yard.

A: Borers that you find in firewood are usually attracted to dead and dying trees. They are the decomposers and insects are very important in nature to help break down these trees along with help from fungi and bacteria. It is unlikely they will attack live trees in your yard although I wouldn’t recommend stacking the wood next your trees if you can avoid it. One of the potential and likely causes of the recent bark beetle infestations of Aleppo pines in our area is the transportation of infested firewood from the ponderosa pine forests in the mountains to our low desert environment where the Aleppo pines grow.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@cals.arizona.edu

Q: I have a Chilean mesquite that’s about 6½ years old. The branches are getting so low that they touch the ground. Is it OK to prune off those lower branches? Somebody told me that you should not prune them very much.

A: It’s all right to prune them in order to correct the shape a little bit, and you can take off those lower branches. You probably also want to open up the canopy a little so that the monsoon winds don’t do a lot of damage.

For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert for 25 years, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program, heard locally from 8-11 a.m. on KNST-AM (790) in Tucson and KGVY-AM (1080) and -FM (100.7) in Green Valley. Call 888-767-4348.

Q: We have some old mesquite trees and palo verde trees near our walking lanes. There are old clay unsealed sewer pipes nearby at a depth of about 4 feet. Are we at risk for sewer problems? How far should any tree be from a lane with old sewers? As for new trees, we were thinking of planting more of the above but not near the walk lanes. Desert willows were also suggested, but they may need more water. Do you have any other suggestions?

A: Your sewer pipes are at risk with tree roots nearby. Typically, mature tree roots extend 2 to 3 times the width of the crown so it is wise to give any potential obstructions such as sewer pipes, sidewalks and houses enough room. Since the trees are old and so are the pipes, you might wait and see if a problem presents. It is certainly a good idea to have the pipes inspected or monitor the water use rate if you suspect a leak. There are quite a few choices for low water use trees. The decision usually begins by measuring the space you have available both below ground and above ground. The mature size of a tree should be accounted for in any plan to plant. Desert willows are a low water use tree and a good one if your space isn’t large enough for a mesquite tree. Other species to consider include white thorn acacia, ironwood and Texas ebony. Your plan should also include irrigation even though you are planning to go with a low water use tree. Even native desert species need some water.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to

tucsongardensage@gmail.com

Q: A large mesquite in my backyard has grown to the point where its roots are lifting up the concrete paving all over the yard. What can I do to stop this from happening?

A: The problem is probably going to get worse as time goes on. You need to dig down all around the tree and cut off some sections of the roots. But don’t get too close to the tree if you want to keep that tree alive and growing. Cutting too close to the trunk can kill the tree. You only want to cut roots that are less than a third of the diameter of the trunk in their thickness.

For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert for 25 years, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program, heard locally from 8-11 a.m. on KNST-AM (790) in Tucson and KGVY-AM (1080) and -FM (100.7) in Green Valley. Call 888-767-4348.

Q: I have been buying firewood (mesquite and eucalyptus) to burn some and use some for woodcrafts like lathe-turned vases. It is common for the wood to be full of large round and oblong holes that are caused by some type of insect. Recently I was able to extract two almost whole grubs of some sort from a piece of mesquite. One “grub” is essentially round, and the other has a large head, sort of triangular, and a smaller round body. Can you tell me what these are and if they pose any danger to my house? Is there anything I can do to get rid of them?

Also, I cut some fresh mesquite last spring and left it in my garage to dry over the summer. It became riddled with small circular holes, apparently caused by some different insect. In this case the damage is pretty much limited to the early, or sap wood. Can you also give me some information about the insect that causes this other type of damage?

A: The two grubs are representatives of common wood-boring beetles from the Buprestidae and Cerambycidae families of insects. The round one is a larva of a long-horned beetle and the one with the large head is a larva of a metallic wood-boring beetle. Both of these insects are associated with dying or dead trees. Their galleries can be seen on sapwood, as you described, and the adult beetles are commonly seen emerging from firewood. They are not known to infest or reinfest dry wood so your home is safe. The small circular holes are from bark beetles, another species commonly associated with dying and dead trees in our area. In the forest, these three are examples of insects helping decompose trees into soil. Without them and the associated fungi and bacteria, we would be up to our eyeballs in timber and our soils would have even less organic matter than usual.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email him at csongardensage@gmail.com

Question: I occasionally run across a dead branch on some of my mesquite trees. The dead branch sticks out like a sore thumb, and on closer inspection, there is a ring around the branch etched into the bark. The foliage in front of the ring is dead, but behind everything appears fine. First, do you know what causes this? Second, should I be concerned. And third, should I be preventing this and how? Right now, all I do is prune the branch out.

Answer: The ring etched in the bark is the work of the mesquite twig girdler (Oncideres rhodosticta). This beetle is in the family Cerambycidae that are commonly referred to as long-horned beetles due to their long antennae. The adults aren’t commonly seen on the trees although they are attracted to lights at night if you want to find them. The female chews a ring in the stem and deposits her eggs further out on the stem. The eggs hatch in the stem and the larvae feed on the dying wood in the stem caused by the girdle cutting off nutrients to the end of the branch. The larvae will overwinter in the wood and adults will emerge in the spring. Research has shown the damage has no affect on the health of mesquite trees and it is simply nature’s way of pruning. So the good news is you don’t have to do anything to prevent these beetles from chewing on your trees.

Peter L. Warren is the urban horticulture agent for Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com

Q: I found a very strange looking caterpillar crawling across my patio. I would like to know where it came from and if it is a problem.

A: The caterpillar you found is Sphingicampa hubbardi and is also known as Hubbard’s small silk moth or the mesquite moth. It is a Southwestern species in the Saturniidae family of silkworm moths found from extreme eastern California, southern Nevada, and southern Arizona into west Texas. They feed on honey mesquite and some species of acacia and related legumes. They are not common enough to be considered a pest. The adult moths have gray front wings covering bright red hind wings that they likely use to shock and awe predators while they make their escape.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@ cals.arizona.edu

Q: We have tons of mesquite pods and they are a huge pain. A yard guy we met said he could spray the tree next April and that would take care of it. Then I read that spraying doesn’t work well on Mesquites because the timing has to be accurate and the pods mature over too broad a time period. Also, our tree is huge and I worry about the spray harming nearby plants. What do you say?

A: The spraying doesn’t work well on most trees, it is costly and time consuming, and it could harm surrounding plants and other organisms, depending on the chemical used and if not done correctly.

There are many factors at play including timing, environmental conditions, and making thorough applications. Due to the gradual development you mentioned, it might take repeat sprays to do a sufficient job. It would likely be more environmentally sound and cheaper to hire someone to rake the pods. Another alternative is to harvest the pods before the monsoon begins and have them milled into mesquite flour. Mesquite flour is a popular alternative to wheat flour among local and heritage foodies and a nice gluten free alternative for those that require one in their diets. Milling events are available in various locations during the harvest season and they charge a nominal fee to grind them for you.Check out DesertHarvesters.org for one group that does this and instructions on how to harvest.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@cals.arizona.edu.

Q : Recently I noticed, on two mesquite trees, a tarry-looking seepage coming out, and in some cases dripping onto the ground. What is it, and what if anything should be done about it? The only thing I can think of regarding care of the trees that might have some bearing on the matter is that they were not watered this spring, and in fact have been without significant (added) water for several months, and have looked a bit less robust than usual this spring in terms of leaf output.

A: What you are seeing is called bacterial wetwood or slime flux. Slime flux is caused by the infection of sapwood by several bacteria and is a problem with mature mesquites. The disease-causing microorganisms are found in the soil and probably gain entry above or below the soil line through wounds or pruning cuts. After several years, affected areas will exhibit a water-soaked appearance (wet wood). Gas is produced by the bacteria (and possibly yeasts) that force out a foul smelling liquid from cracks and wounds. The liquid is dark brown to black in color.

Infected trees live many years and slime flux is more of a nuisance that requires periodically a strong, hard stream of water to prevent staining of patios and cars. Seriously infected branches may need removal if they present a safety hazard. The old remedy of placing drainage tubes into the infected areas is not recommended, and may in fact, present more entry sites for the disease.

Regarding the water schedule, I recommend a good soak of the root zone out near the edge of the crown of the tree every three weeks during the growing season down to about 36 inches. Of course you can hold off during the monsoon season if you get good rains and during the winter as well.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@cals.arizona.edu.

Q: Can you identify this insect? It’s beautiful, gentle and somehow makes me think of an acoustic guitar. There are perhaps 30 of them in the main crook of a tree at my home.

Ar: These giant mesquite bugs (Thasus neocalifornicus) are a common sight in desert southwest landscapes, particularly on mesquite trees during May-August. These large bugs commonly aggregate in family groups and look impressive that way with their brightly colored nymphs. Despite their name, they may also be found on other garden and landscape plants.

They cause no significant plant damage, are harmless to humans, and do not have a venomous bite or sting so enjoy these bright highlights on our mesquite trees.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@cals.arizona.edu