Q. About a year ago you helped us diagnose a spider mite problem on our creosote bush. We took care of that as you directed. The results were encouraging and seemed to get the problem under control. However, we think the mites have come back with a vengeance and considering a severe pruning to revive it. Creosotebush cut down probably with a grader in the front and unpruned creosote bushes in the back. A.  Creosotebush can be cut back to a few inches above the ground and it will grow back after a few occasional waterings. Look at the creosotebushes mowed off near desert roads probably by a road grader from the DOT. Because they were cut down and got some extra water from the road when it rained, they came back like gangbusters; dense and green. Predator/Prey             What concerns me more is why the spider mites got out of control in the first place. Creosotebush has its share of spider mites naturally, but they are frequently controlled by predators such as other insects and mites. However, in your case, the balance between “good guys” and “bad guys” got out of hand with the “bad guys” winning.             The problem with spraying a pesticide is killing off the “good guys”, then the “bad guys” get out of control because few or no predators are left. So, we usually avoid spraying pesticides unless we don’t have any choice. Cutting Back Creosote             I like your idea of cutting it back and letting it regrow. But I think you also must do something different or the spider mites will just be back again. Weed Control             Control weeds in the area. Spider mites like to feed on many kinds of plants including weeds, and these can play host to a growing population of “bad guys”. Secondly, be careful of watering too often. Creosote bush should never be on an automatic irrigation system because it just doesn’t like to be watered that often. Water it no often than four times a year with three of those irrigations during the hot months.

Q. Is it common for the Chitalpa tree to partially defoliate in the summer? What would be the optimum amount of water for 15-foot Chitalpa tree growing in Kingman, Arizona? Not the readers chitalpa but s picture I had. A. Chitalpa, like some African sumac, is notorious for leaf drop in the middle of summer. According to several authorities from New Mexico and Arizona this is common with this tree. Bacterial Disease             According to the plant pathologist from New Mexico State University, this tree has a bacterial issue that causes some of its water tubes to get plugged. This causes the leaves on the tree to get scorched like it’s not getting enough water and in severe leaf scorching, the leaves drop.             It’s similar, if not the same, disease we see on grapes called Pierce’s Disease. You can try giving it more water all under its canopy and see if that helps. If it’s a lack of water because it’s not getting any you will see the tree improve. Anyway, apply enough water to wet the soil under the canopy a depth of 2 feet. Spread to Grapes             From what I understand there is no cure for this disease and  ach plant has it because of how it’s propagated. Some scientists think this disease may be transmitted by a small insect similar to a leafhopper. So, get rid of any weeds growing nearby to the tree. It is possible this disease could be spread from your Chitalpa to nearby grapes. The symptoms are similar; leaf scorch and leaf drop but in grapes its eventual plant death.