Ferocious-looking bugs help the garden

Mulch is available to the general public free of charge at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas. It is located outside of the orchard fence and can be picked up anytime. The mulch is recycled wood chips from trees removed from residential landscapes by local arborists. Four or 5 inches of wood mulch helps keep desert soil cooler, conserves water, reduces weeds and windblown dust, and adds organic matter back to the soil.

I received a question from a reader that was forwarded to me by the Las Vegas Review-Journal Home section. Unfortunately, I did not receive a return address so hopefully Mr. Atkins will read this particular column. I receive most of my questions via e-mail at morrisr@unce.unr.edu. If you do not have e-mail, questions can be sent to me at the University of Nevada Cooperative Extension; you can get the address by calling the master gardener help line at 257-5555.

Mr. Atkins sent me some insects that he had collected from his yard and asked me if they were bad bugs. The insects were immature ladybugs, which are also called ladybird beetles. These immature ladybugs are truly ugly and ferocious looking on a small scale but they are voracious eaters of all sorts of soft-bodied insects including aphids. So, it goes without saying, these little guys are really good little guys.

Q: I have a regular willow tree that I have had for about four years. Every year, it has put on a beautiful bunch of new leaves. This year, it looks like it is having problems getting leaves all the way out to the ends of some limbs. It has a lot of leaves near the trunk but less out farther. I give it plenty of water and treat it with Bayer borer pesticide. I see no indications of borers at this time. We are supposedly having an aphid infestation in the valley this year. Would that cause any problem for the willow?

A: Aphids will not cause this type of problem. In our climate, aphids are relatively short lived due to the heat and low humidity.

First of all, this is not the appropriate climate for regular willow trees. Many willow trees are from northern climates and get to be huge. If they were to live out their lives, they would be too large for residential landscapes. Besides, they are just really out of place in the desert. They are more appropriately planted along waterways in northern climates.

These types of willows grow fast, have weak wood that breaks in strong winds, and are just messy, dirty trees. They do get aphids and these aphids drip honeydew on anything below them. The honeydew is sweet and attracts bees and ants.

These trees frequently sunburn in our climate and always get borers. The borers cause limb damage, which is followed by diseases and limb dieback.

Just because you are using a chemical for borer control doesn't mean it's going to work. If you are applying it as a granular pesticide to the soil, it frequently gets bound up in wood mulch making it ineffective. The borer that typically gets into willows is called a clear winged moth and is usually not controlled by this chemical. On top of all this, if you don't apply it at exactly the right time, you most likely will not get any control from it.

Diseases that get into willows typically are not easy to control. They usually do not kill the tree, but they cause severe limb dieback and the tree gets so unsightly you end up removing it. Take a look around. You do not see any old willow trees in the valley. There is a good reason for this. Cut your losses now and remove the tree.

Q: We have lemon, orange and grapefruit trees. Our lemon tree is doing great but our orange tree is not doing that well. We have had these trees for 13 years and just started to get oranges and grapefruit last year.

A: The Las Vegas Valley is not citrus country. It is just too cold here unless these trees are protected. In order to get citrus to grow here, these trees need to be located in warm microclimates in residential landscapes and protected from wind. Both freezing temperatures and wind can play havoc on citrus.

You did not tell me, but I am assuming that this is a Meyer lemon, which is not a true lemon. Meyer lemon is one of the most cold-tolerant citrus trees and it would be a good one to experiment and have fun with. Grapefruit is relatively cold tolerant as well, but not quite as much as the lemon. Due to its extreme cold hardiness, another good one would be kumquat, but it is more limited in its popularity.

Oranges vary a lot in their tolerance to freezing temperatures. The more cold-tolerant orange would be satsuma mandarin orange, not the Washington or navel type. Satsuma orange can handle temperatures down to the mid-20s. Temperatures below this will mean damage to the tree. It usually will bloom sometime in March so if we get a late freeze, you would lose your crop for the year.

The bottom line is to make sure when these trees are planted into soil that has been prepared thoroughly with compost and has good drainage. Plant them in locations that are warm and not windy; do not plant them in rock mulch where the radiated heat in the summertime will just hammer them when they are young.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at extremehort@aol.com.