Skeletonizer damages leaves of yellow bells

Q: From a distance, I thought my yellow bells and orange bells shrubs weren’t getting enough water because the leaves started turning brown. But when I looked closer, I’m wondering if the brown leaves are because of a fungus on the leaves. Any thoughts?

A: Look at the leaves of your Tecoma, aka yellow or orange bells, more closely and I think you will see that the surface of the leaf has been eaten or skeletonized. This chewing damage causes the leaves to turn brown; they become brown faster when it’s hot out.

At a distance, you see the leaves of your Tecoma turning brown and it may look like drought. Upon closer inspection, you get more detail and can see the insect damage to the leaves and not a disease.

This shrub is native to the Sonoran and Chihuahua deserts, the Southwest, central and even the northern parts of South America, but not the Mojave Desert where it needs slightly more water and warmer winter temperatures. Tecoma and this skeletonizer coexist together.

The skeletonizer is the younger stages of a moth. It’s not clear if this insect will survive the low temperatures of our winter or not. If it does, we may see more of this insect damage in future years as more Tecoma are planted.

This insect damage is common to Tecoma in warmer parts of the Southwest. It’s feeding damage by the young — or larvae — of a moth given the common name Tecoma leaf tier skeletonizer. This damage is like the skeletonizer damage we see on grapes but caused by the young of a different moth.

Right now, this insect doesn’t usually cause enough damage to warrant spraying an insecticide. Just pull off leaves when damage appears and drop them on the ground. If the damage gets worse in future years, then spraying might be warranted.

The pesticides of choice are natural insecticides called Bt and Spinosad. Apply these sprays just before you anticipate damage or at the first sign of damage. Bt and Spinosad products will kill the larvae of any moth or butterfly whether it’s a good or bad one, so be careful.

Spinosad can be hard on honeybees so don’t spray plants that are flowering and spray at sunup. If you have no choice when to spray, and the plant has flowers, remove them; more flowers will be produced later.

Q: How much fertilizer should I give my trees in the landscape and when can I do it now?

A: Apply fertilizer to established, winter-hardy landscape trees late in the season when temperatures have cooled down and trees aren’t growing anymore but still have leaves. This is called a late fall fertilizer application and substitutes for a spring fertilizer application. In the Las Vegas Valley, this would be around late October to the middle of November.

Apply it to the soil after an irrigation by using a sharpened, round-nosed shovel. Push the shovel into the ground as deep as you can and push it forward. Drop a half cup of this fertilizer in the slit made by the shovel and close the slit with your foot.

If the tree’s canopy is 10 feet in diameter, use two half-cups of fertilizer, one on each side of the tree, 2 feet from the trunk. If the tree’s canopy is 20 feet in diameter, use six half-cups of fertilizer, three on each side and spaced about 2 feet apart. If the tree’s spread is 40 feet in diameter, apply 24 of these half-cups in wet soil under the canopy. Turn on the irrigation water in a normal irrigation cycle, let it dissolve the fertilizer in the soil and carry it to the roots.

Q: I have a raised planter box with tomatoes that are doing quite well. Some critter is raiding these tomatoes nearly every night and removing the fruit. I found one of my larger heirloom beauties half-eaten and dropped outside the box about 20 feet from the plant. What kind of critter might be big enough and strong enough to do this?

A: I would first suspect rats. Rats are common throughout the valley. They are probably the second-worst problem after birds, and they will eat anything from fruit and citrus to vegetables including tomatoes and even fresh compost ingredients. Normally, though, they eat fruit still attached to the vine, but they can carry the fruit if they must. But because of their teeth, damage to the fruit is telling.

The two types of rats are the roof rats and Norway rats, with the smaller roof rat being more common. Regardless, these critters go after ripe or nearly ripe fruit. If food becomes scarce, then these critters will go after unripened fruit as well.

Two nonlethal strategies that might work include getting rid of any hiding places such as low-lying and dense shrubbery or piles of debris and harvesting fruit before it becomes fully ripe. Harvest tomatoes when they are still green, provided the green fruit is starting to change color, and they will still ripen off the vine. This color change occurs first near its attachment to the mother plant, called the shoulder, and spreads over the rest of the fruit as it ripens. Harvesting fruit early reduces the chance critters will eat them.

Rats are good climbers so if you enclose a tomato plant with a cage to restrict their smorgasbord opportunities, use hardware cloth with holes smaller in diameter than your thumb but large enough to allow pollinator entry.

There is a lot of information on the internet concerning repellents from mothballs to fox urine. Like any information on the internet, you are likely to have mixed results so beware.

Regarding lethal strategies, snap traps seem to work the best and maybe the safest method to use if other animals are around.

Q: My father’s lawn is tall fescue and completely went dead this summer. I’d like to know what we did wrong because we watered twice a day. We are anxious to plant a new lawn ASAP and want some advice on how to plant a new lawn from seed and the best seed to use. The lawn gets full sun.

A: Whatever killed the lawn is most likely gone. I know you watered twice a day, but the death of an entire lawn during the summer is nearly always due to an irrigation problem. There are diseases and insects which cause damage, but they always leave behind telltale patches of green. These patches of green, to a trained eye, are clues to the cause of dying grass.

Wait until the temperatures cool down a bit, perhaps sometime between late September and mid-October to begin planting a new lawn. In the meantime, leave the dead grass in place to shade the soil and prevent weed growth. This layer of mulch reduces weed problems that might pop up if you were to remove it. In the meantime, continue irrigations because there are probably plant roots in that dead lawn that need the water.

Check the irrigation system and make sure it’s working properly and the irrigation controller is functioning. Kill and remove any weeds in the new lawn area. If using a weedkiller, spray a week in advance so the herbicide has time to disappear before planting.

The day before planting the seed, irrigate to soften the soil. Rent a core aerator to punch holes all through the lawn area and rake it to remove or break up these cores.

Apply 10 pounds of fescue seed blend per thousand square feet of lawn area. Don’t skimp on the cost of grass seed. Good grass seed is expensive. Bad grass seed is cheap.

This is also the time to apply a fertilizer on top of the grass seed if the compost is not a rich compost. If the compost has fertilizer in it (a rich compost), don’t apply any fertilizer. Cover the seed with a ⅛-inch layer of compost and water twice a day. When the grass starts coming up in about five to seven days, reduce irrigations to once a day in the morning.

You will see grass emerge first in areas where there is good irrigation coverage. Where the grass is growing slowly, work on improving the irrigation system for better water coverage. Mow the grass no closer than 2 inches when the grass reaches 3 inches tall. Mowing causes the lawn to become denser.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.