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Ask the Experts – January 2018

By Kelly Young

A neighbor recently speculated that our oleanders were infected with a blight and should be removed. Although some of the leaves are yellow, I don’t see what the problem is. Could he be right?

Oleanders are affected by a number of diseases. Among them is oleander leaf scorch, which is caused by the bacterium Xylella fastidiosa. The bacteria are transmitted from plant to plant by sap-feeding sharpshooter insects. Leaves infected with OLS turn yellow along the edges and die. There is no treatment; infected plants should be removed. The symptoms of OLS are similar to salt burn, which is caused by insufficient irrigation or exposure to salty water, such as backwash from a pool. Definitive diagnosis can only be made by a plant pathology lab, which may be pricey. First, check the irrigation system servicing the oleanders to make sure the plants are receiving enough water. To learn more about how to adequately water your plants, visit the Arizona Municipal Water Users Association website at amwua.org.

Over the past several years, the fruit on our Eureka lemon tree have developed bumpy, thick skin and produce very little juice. What can we do to restore their original quality?

Many citrus trees in Arizona are grafted onto “rough” lemon rootstock. Although edible, rough lemons are not as attractive as the Eureka variety and generally produce a less desirable juice. Maintaining grafted fruit trees requires removing shoots that originate below the grafts. Do a close inspection of the tree to find any branches that still produce Eureka lemons. If you don’t find any, you can remove the tree and replace it with a true Eureka cultivar, being sure to carefully prune out any suckers, or choose to live with marginally acceptable lemon juice.

My homeowners association says I need to remove the wild grass that blankets the gravel in my front yard. It is bright green and very soft, and it doesn’t grow very tall. How can I convince my HOA that I shouldn’t have to take out something so lovely?

Each winter, a carpet of Mediterranean grass (Schismus barbatus) covers the floor of many desert landscapes throughout Arizona. Although green and soft as you described, Mediterranean grass is not native to the Southwest. Considered a weed, it readily reseeds and returns in greater numbers year after year, spreading into neighboring areas. Fortunately, this low-growing, weedy bunch grass is easy to pull out and surrenders readily to a hoe. If you do nothing, the plants will dry up and die once springtime temperatures reach approximately 90 degrees. To avoid reseeding, it is best to remove the plants before the seed-producing spikelets appear in the spring.

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