Lack of water likely to blame for brown leaves

Fall classes for the University of Nevada Cooperative Extension’s master gardener program are quickly coming up. Registration will take place Monday, Aug. 10, from 9-10 a.m. at the UNCE Lifelong Learning Center, 8050 Paradise Road. Classes are scheduled for 9 a.m. to noon on Mondays, Wednesdays and Fridays for eight weeks beginning Sept. 14.

The master gardener program teaches sustainable desert gardening practices, including proper plant selection and care, disease and pest management, and water-efficient gardening. To become a master gardener an individual must complete 72 hours of horticultural instruction and volunteer 50 hours on community projects each year.

Please preregister for the Aug. 10 meeting by contacting Mary Bertsch, program assistant, at 257-5501 or bertschm@unce.unr.edu.

Q: I don’t have too many problems with my plants but right now I’m very concerned about my Little Gem magnolia. The tree is 10 feet tall, in the ground five years, in full sun and surrounded by 2 feet of circular open space before a flagstone patio begins. Based on your column, I replaced the rock around it with wood mulch and changed the emitters from four to two. Now the tree does not appear to have much new growth and is not very dense. The leaves are changing from bright green to pale green, then brown and dead. Branches are also dying from the bottom up. It does not seem to be a pest issue.

A: If you have been following my column or newsletter, you will know I am not a big proponent of magnolias in this climate. They never live very long here.

To me it sounds like a water problem. I think in your case it may have been a mistake to go from four to two emitters. At about 10 feet tall your tree should get about 30-40 gallons at each watering.

To find out if it is a water issue, flood the base of the tree with a hose twice a week for the next couple of weeks. I guess you will start to see some new growth and the canopy begin to increase in density.

I would also put down iron around the base of the tree near the water sources next January. If you missed that application this year, then do it now.

You could try spraying the foliage with foliar fertilizer as long as it is applied very, very early in the morning and applied lightly. Or you can put the fertilizer at the base of the tree near the water sources. In fact, that might be a bit safer for the plant. Use Miracle-Gro or a similar product.

But, I do think it is not enough water applied and/or not frequently enough. I would be watering twice a week right now if you have put down mulch. It sounds like a hot location for a magnolia.

Q: I have beautiful plants that are just loaded with tomatoes but the fruits are damaged. It seems some type of worm is eating a small round hole in each of them and then the worm lays eggs on the tomatoes. I bought some Sevin, but after reading the directions, I decided I really didn’t want to use it. It seemed to be pretty potent stuff. Do you know what this worm is and what I can use on them to get rid of them?

A: This is probably tomato fruitworm, also called corn earworm when on corn and eating the silks. I have sent you some pictures of tomato fruitworm damage on tomato.

Spray the plants with Dipel, Thuricide or Spinosad, which are all organic. This also will take care of tomato hornworm, which is now attacking the foliage of tomatoes, grapes and other plants. Spray in the early morning or late evening hours.

Q: My gold lantanas are doing very well so far but the purple lantanas seem to be withering out. Am I watering too much or too little? I have been watering for six minutes in the morning and six minutes in the afternoon.

A: Telling me that you water for six minutes is like telling me that you would like to drink six minutes of coffee in the morning for breakfast. I have no idea how much six minutes of water is.

At a rate of one-half gallon of water per hour (the lowest rate for drip emitters and assuming the plant only has one emitter) would mean you are giving it one-tenth of a half gallon (6.4 ounces) of water in the morning and 6.4 ounces in the afternoon. This is less than a cup each time you water.

If your emitter is a 5 gallon per hour emitter then you would be giving it 64 ounces of water in the morning and 64 ounces in the afternoon. If this is an adjustable emitter, then I have no idea (and you would not know either) how much water you are giving your plant.

At this time of the year for lantana, it probably should receive about 1 gallon of water per plant every two to three days, depending on your soil. Sandy soils need water more often. Heavier soils less often.

There is no reason to water woody landscape plants daily and they should not be watered daily. Daily irrigations this time of year would be reserved for lawns, vegetables and other shallow-rooted plants.

You will need to learn what type and how many emitters are on your plants to determine the quantity of water delivered, not the number of minutes the system is being run. Drip emitters are designed to run for hours, not minutes. Sprinklers run in minutes since their rate of delivery of water is much higher.

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 morrisr@unce.unr.edu.