Q: I am writing to inquire about recommendations for a nontoxic approach to controlling citrus leafminer on a young lime tree I am growing in a large pot. I do not recall having this pest in the past and have had limes, grapefruit and lemons for many years. This new lime tree I planted about a year ago is now infested on all the new leaves and I am wondering if there might be a nontoxic method to reduce or eliminate them. I have looked up information on the web but the recommendations seem to be relatively toxic and I would prefer to avoid those if possible.
A: Because your lime tree is young, insecticides are generally recommended to prevent these insects from slowing the growth of the tree. That said, you could let your tree tough it out since there are natural enemies that prey on the citrus leafminer and the leaves they damage are still effective food producers for the tree.
Other things you can do to manage the situation include avoiding pruning except for water sprouts and branches broken by wind, et cetera, and only fertilizing outside of the normal flights of the adults. The adults are most often seen in the summer and fall months. Both pruning and fertilizing promote the new growth that is most attractive to these insects.
Q: When is the correct time to prune roses in the Tucson area? And do you prune them like we do in the Midwest, i.e. cut back near the ground?
Answer: The pruning of roses is recommended twice per year in Tucson. The first pruning can be done in late January to a height of 15 inches or so. This time remove all dead wood, crossing branches, and small leaves. Seal the fresh pruning cuts with Elmer’s glue to prevent insects from invading the newly cut branches, fertilize, and then water.
In mid-September a lighter pruning is recommended. This time remove one third of the plant along with any diseased or dead wood but leave any leaflets. Seal fresh cuts with Elmer’s Glue, fertilize, and water.
The Pima County Master Gardeners teach classes on roses and other things at some of the public libraries in case you’re interested. Check your library schedules or call the Extension Office for more information,626-5161.
Q: We are snowbirds here November through March. Much of our landscape was redone the last week of March and we departed April 3. Now we have just returned and I see our 5-gallon emus (red valentine shrubs) have bit the dust and a couple red barrels are dying. These plants should have been sturdy enough for their western exposure site. Our new sprinkler system is one year old and works fine. Would you guess that these plants should not have been planted so late in the spring before we left right away? Perhaps they needed two to three daily waterings on hot summer days but no one was here? Our gardener/landscaper didn’t indicate that there should be any problems and he knew we are here just part time and he set the sprinklers.
We both chose the plants together and he knew we were leaving immediately after he installed the landscape. He wasn’t able to schedule our work sooner and I think maybe the job shouldn’t have been done after late January to allow the plants to settle in before the heat hit.
A: The last week of March and into April we were seeing temperatures in the high 80s and low 90s. If your irrigation was working properly and delivering the right amount of water then you might have been OK, although western sun exposure is a tough place to get started when it gets hot.
Drip irrigation is the preferred method rather than a sprinkler and the recommended amount for the summer season is once every 14 days to a depth of 12 to 18 inches for the barrel cacti and 24 to 36 inches for the emu shrubs. The barrels (Ferocactus species) are certainly desert plants and the emu (Eremophila maculata) is from Australia and a good desert adapted plant so their chance of survival in your area is good.
You are asking the right questions and if you are planning to try again, I recommend planting earlier, maybe now, so they can get established before the summer and make sure to adjust your irrigation to fit the needs of the plants.
