Grub Control in the Landscape

Q. I found grubs in the soil with many established plants. Are these just a seasonal thing? How do I get rid of them now and prevent them in future? Are some plants more susceptible than others? 

A. I will tell you is much as I know about them. Their adult form is a large flying beetle called a chafer or June beetle that you see in June and July. Their immature form is a white grub that feeds on dead organic matter in the soil, but I think also will chew on tender roots of plants like Lantana.

            A few of them munching away on some plant roots here and there causes little plant damage. In fact, you won’t even know they are there. It’s when several feeding on the roots of one small plant, or your landscape is inundated with them that you start to see plants struggling or even dying. So, unless there is a problem I would leave them alone.

            There are biological control pesticides such as bacteria (several commercial names of products available such as Grub Control) and nematodes (mostly online sales) that you can use in place of conventional insecticides like Sevin. They may take a year or two to get fully established in the soil.

Key Lime Irregularly Producing Fruit from Year to Year

Q. I have a key lime tree that’s 4 years old.  The first year it was full of fruit.  The next 2 years no fruit, then this year only 3-4 limes.  My neighbor has a regular lime tree full of fruit.  What’s wrong?

A. Freezing temperatures in the spring. If you have several light freezes that go through the valley in the spring you will have no citrus fruit. If you have one freeze that goes through the valley in the spring you will have some fruit.

Desert Water Requirements for Establishing Sago Palm and Bay Laurel

Q. I would like some more of your expert advice if you have time. As part of our landscape renovation completed last November, a Sago Palm and a Bay Laurel were planted. The Sago Palm is approximately 7" in diameter and 3 feet tall while the Bay Laurel is about 4 feet tall. They both have one drip near the base and two further away with 1 GPH Emitters, They are watered for 90 minutes following the water district watering schedule for lawns this first year. Is this adequate watering and what would you recommend as the plants grow?

A. If you are watering for 90 minutes then I would recommend four each, 5 gallon per hour emitters on the Sago palm placed about 12 inches from the trunk in a rectangular spacing for the first year after it is moved. The second year I would keep the same emitters but move them out to about 18 inches from the trunk. Unlike the Bay Laurel the amount of water will not change as they get taller. 

Make sure the hole dug for the Sago palm is three times the width of the root ball. Make sure the soil is amended with compost at the time of planting with one shovelful of compost mixed into 2 to 3 shovelful's of soil for the backfill. You will use this ratio of compost to soil also on the Bay Laurel.

Bay Laurel Water Use

The Bay Laurel is still quite small and so about 15 gallons per application is all that is needed. However, in two years you will bump that up to 30 gallons per application as the tree gets larger. Because the Bay Laurel will be a larger tree I would recommend using drip tubing coiled in a spiral around the tree instead of drip emitters. This spiral of drip tubing will be attached to the mainline spiral around the trunk of the tree and reconnected back into the mainline. Spiraling the drip tubing around the tree and reconnecting it back to the lateral will eliminate the need for flushing for that tree. If the drip tubing dead ends at the tree then the drip tubing must be flushed on a regular basis. 

If you use drip tubing with 1 gallon per hour drip emitters embedded into the drip tubing every 12 inches then you will only need about 10 feet of drip tubing spiraled around the tree to give you 15 gallons of water in 90 minutes. If you use drip tubing with drip emitters spaced every 12 inches and the drip emitters emitting 1/2 gallon per hour then you will need about 20 feet of drip tubing spiraled around the tree. The spiral should be staked so that each spiral is about 12 to 18 inches apart around the tree. 

Personally I would use the 1 gallon per hour drip tubing with emitters spaced 12 inches apart. It's very easy to come by locally. As the tree gets larger every two or three years you will splice in another spiral of drip tubing To give it more water because it's larger.

Pollinators vs Pollenizers and Citrus

Q. I reached out to you a couple of years ago regarding the lime and lemon trees we planted about three years ago.  Here they are, both are filling out and growing taller.  My question is why no fruit?  This year we had two tiny limes and no lemons.  We follow fertilizer instructions. The tag on the lemon and lime trees stated pollination not required.  I understood that bees are not required.  We do not recall a freeze last spring.  

A. Citrus of all forms does not grow well in the Las Vegas Valley. You will have good years and bad years. If there are freezing temperatures in the spring you will have spotty production of fruit. If it's a warm spring with no freezing temperatures than you will have good fruit set if you saw flowers. If you saw no flowers, there will be no fruit. 

All Fruit Trees Need Bees

When you see flowers make sure that you see some honeybees. To attract honeybees to your yard plant some rosemary or other herbs that flower during the winter time that attract honeybees. Put out a tray of water and change the water weekly to keep it clean. Water will also attract honeybees but flowering plants in the winter that they like are better.

Las Vegas is Not Known for Citrus Production. Why?

FYI if we didn't have freezing temperatures here there could be a vibrant citrus production area. That production area in the desert occurs in Yuma where it's less likely to freeze in the spring. Winter temperatures in Yuma, Arizona, are warmer than they are in Las Vegas. Citrus are subtropical. Any fruit trees that produce flowers before freezing temperatures are finished are likely to not produce fruit. That's true for peaches, apricots, nectarines, plums. It's a basic rule of fruit science.

Pollenator vs Pollenizer

Saying that the trees don't require pollination means that they don't require another tree to make fruit. They will still need honeybees as pollenizers not pollinators. Pollenizers are insects. Pollinators are other trees.

Freezing Temps Can Happen at Sunrise

Had one freeze that came through this past spring. It's very easy to miss if you're not looking for it. The coldest temperatures are just before sunrise. After sunrise the temperatures get warmer. Use an inexpensive low temperature thermometer and check for yourself.

Desert Horticulture Podcast: Summer Heat and Brown Plants

 Summer heat can be brutal on plants. Maybe it isn't always the heat.

Where to Get Woodchip Mulch in the Las Vegas Valley

 The University Orchard is located 100 yards east of the corner at North Decatur and Horse Road in North Las Vegas in Aliante.

Mulch Update: open at 7 AM! Load your own: please bring your own tools to fill your own containers! Tractor filled pick-up trucks by appointment: call 702-786-4361.