Thrips cause scarring on nectarines


Q: Do you know anything about a grass seed called CanadaGreen I saw for sale in a magazine? It says it sprouts and covers the area in 10 days and can survive from 120 F to 40 below zero. Is it any better than selections available at stores here?

A: I did a little background check on this grass. You can say anything about anything you want when you are marketing, but if they don’t tell you what kind of grass is in the bag , you have no way of knowing if it will work in Las Vegas.

So, not knowing the grass, I did find a review by someone who bought some seed and quoted what was in the bag. State seed laws require that you must state the percentages of grasses on the label , its germination percentage, percent weed seed, etc. However, an advertisement doesn’t have to.

This seed is nothing special. It includes 53.2 percent creeping red fescue, 23.4 percent annual ryegrass, 14.1 percent perennial ryegrass and 4.4 percent Kentucky bluegrass. The reason it comes up fast is primarily the annual ryegrass. You can find the same mix of grass seed, called Shade Mix or something about shade, at your local hardware or grocery store.

Annual ryegrass is considered a “nurse grass” by some because it comes up quickly and provides some protection for slower-germinating grasses. Many people consider it a weed. It is an inexpensive grass, used in Las Vegas for overseeding Bermuda grass for winter color.

It is an annual grass and does not handle heat very well and, when used for winter overseeding, dies in early summer when temperatures hit 100-plus F. Besides that, it is really not pretty . It is light green, never gets dark green and looks rough when you mow it.

Creeping red fescue will not survive Las Vegas summers. It is considered a shade grass and will die at the same time as the annual ryegrass .

The third is perennial ryegrass, and it might survive the summers in Las Vegas depending on the variety of perennial rye. Some are heat tolerant (Palmer and Prelude, for instance) while others are not (Manhattan and Pennfine). If it is not a heat-tolerant perennial rye, it will die when it gets hot. If it is a heat-tolerant rye, then you have a 14 percent winner.

Kentucky bluegrass is very slow to germinate and can take about a month to sprout. It is a good grass for northern climates but is questionable in the hot south like us.

Don’t waste your money. You can find plenty of grass seed locally that won’t work here. At least if you buy it locally, and it dies, you will support local purveyors.

Q: I have an Arctic Star nectarine but the fruit really looks awful each year. How do I make the fruit look better? And is this fruit safe to eat?

A: This particular nectarine is one of my favorite fruits to grow in Las Vegas, and it is one of the more difficult to grow as well. The difficulty is just what you are experiencing. The fruit becomes scarred because of the Western flower thrip.

But let me say something about the quality of this fruit first. When I first tasted it I was blown away. The flavor profiles are absolutely remarkable when it is grown here . My best description would be perfumey. Now I am not a “perfumey” kind of guy, but it has this floral overtone that sets it apart.

It is a white-fleshed nectarine. Typically, like many white-fleshed peaches, I would describe the taste as very sweet and having some almond and floral (I would call them rose) backgrounds.

Nectarine is a hairless peach. It was discovered in a peach orchard as a sport (mutation) growing on a peach tree. The branch with the hairless peach was propagated by cuttings and then used as budwood to make more nectarines.

The hair on a peach that some people object to actually adds protection from insects . Tiny insects, such as Western flower thrips, are so small (narrow and measuring about 1/32 of an inch long) that they have a hard time battling their way down to the skin of a hairy peach.

However, once that hair is no longer there, this insect has no problem getting to the skin of the fruit. Once at the skin, this thrip uses its modified mouthpart to rip and shred at the skin’s surface and lap up the juice from the fruit much like a dog.

Tearing and shredding of the skin leaves scarring on the fruit’s surface as it grows. This scarring is what you are seeing. I have watched thrips start their feeding inside the flowers of peach and nectarine, feeding on the ovary of the flower. As the ovary becomes pollinated and the fruit develops, the hair on the peach keeps the thrip at bay.

However, the hairless peach, the nectarine, does not have this protection and the thrip continues feeding up to harvest. This can cause tremendous scarring and it looks so awful no one wants to eat it. It is, however, perfectly safe to eat.

Controlling the thrip on nectarine requires a spray program . Sprays used in rotation include insecticidal soaps, neem oil and spinosad. I will talk more about control and provide pictures in my blog.

Q: I have two, 3-year-old grapefruit trees that I want to move to another area of the yard.  How far back should I prune them before the move?

A: The purpose in pruning them would be to reduce the tops because you need to destroy part of their established root systems to move them. So by cutting the top back, you compensate somewhat for the partial loss of the root system. If you were moving them without destroying much of the roots, you would not need to prune them back.

However, if you are digging them out of the ground and notice that you have to cut through quite a bit of roots, especially larger roots, then I would take about one-third out of the canopy. I would probably remove limbs that might be a bit too close together.

The type of cut you make will be important. There are two types: one where you remove a branch at the juncture of two branches leaving only one of the two (thinning cut).

The second type is where a cut is made somewhere along the branch, not at a juncture (heading cut). It is best if you use thinning cuts (remove an entire branch or limb), if possible .

This type of cut results in a general thinning of the branches (fewer branches in the area). The heading cut does not result in fewer branches, just shorter branches.

Bob Morris is a horticulture expert living in Las Vegas; he is on special assignment in Balkh Province, Afghanistan, for the University of California, Davis. Visit his blog at xtremehorticulture.blogspot.com.