Watch grapevines for grape leaf skeletonizers

Q: My grapevine has started to leaf out. What is the spray I need to use to prevent the leaf eaters? I saw a black wasp-like bug today.

A: That black wasp-like insect was actually a moth and does not sting. But she will be laying eggs on the undersides of your grape leaves.

These eggs hatch in a few days and the larvae that emerge will begin to consume the leaf from the underside, oftentimes in a row, leaving the leaf veins behind. For this reason we call them grape leaf skeletonizers.

Be careful of these larvae! If they land on your skin they will “burn” and give you a lot of pain on that spot. Use sprays such as Dipel, Thuricide or Spinosad to control the larvae.

These sprays must be directed toward the undersides of the leaves as well as the tops. So plan on two passes over your grapevines: the first time on the underneath side and the second one over the top.

Spray the leaves enough to give the leaf surface a light coating on both sides. It does not have to be sprayed until the leaves are dripping wet. If you have a spreader/sticker to add to your spray then all the better, and it will give you better and longer lasting control.

Both sprays will also control the hornworm that can consume grape leaves voraciously.

Spinosad has the additional advantage of giving you some control of leafhoppers when they are young, if those have been a problem in the past. Bt sprays do not. Make two applications. One now and one more about a week from now.

Q: Does a colder, harsh, longer-than-usual winter affect the growing of garlic? I’ve noticed many of my plants are under-developed or didn’t develop at all, while others have gigantic stalks!

A: In my opinion, cold weather would not cause any reduction in growth or performance from a garlic clove unless the clove was damaged in some way. The only way to check that is to dig out some poor-performing plants and look for potential problems.

Was the clove small when planted? Was there a disease problem on the clove or plant that would cause the plant to perform poorly? Was there an insect problem causing damage to the clove or plant? These all have to be checked.

The size of the clove you plant is related to the eventual plant size and how big your garlic bulb will become. So if you are seeing differences in growth, it would most likely be either a disease, insect or production problem.

Disease and insect problems can be more likely if you save garlic seed from year to year. Plant only large, healthy cloves. Make sure cloves are fully healed or treated with a fungicide before planting.

Rotate vegetables and don’t plant the same vegetables in the same spots year after year. Without rotating your vegetables you will cultivate disease and insect problems in those spots.

Use “certified” garlic for planting. These plants are certified to be free from problem diseases and insects.

If you decide to disregard this advice and plant cloves that are not certified, each clove needs to be inspected carefully for any problems before planting and discarded if at all questionable.

Q: My patio faces mostly to the west and gets four to five hours of shaded and direct sunlight each day. Will pepper plants in containers work well under these conditions? I have read that peppers need up to eight hours direct sun each day.

A: Sunlight requirements for plants are not like an “on” and “off” switch. They will get light from indirect sources as well, so it is hard to say, but you are most likely on the borderline for pepper production.

When you say this is a combination of shaded and direct light, it can make a big difference which it is and how much of each the plant is getting. The amount and degree of shade will have an effect on pepper production. All I can do is to tell you to try it and find out.

If they are going to be in containers and the light is coming from one direction, rotate the container periodically so that the plant will get light from different directions. It will grow more evenly that way.

If you are on a patio and there is not enough light from direct sunlight, you might be able to supplement the light that is needed with a fluorescent light placed a few inches above the plant. You could have it on during hours when the plant is not in direct sunlight.

This might be enough additional light to improve your production or improve flowering.

Q: Last fall I planted five rose bushes and they appear to be doing well. Three of the bushes have one large stem growing from the middle of the bush. Should I cut the large stems back to make the bushes more symmetric?

A: Very strong growth from plants that are grafted on to rootstocks is frequently a sign that the rootstock has sent up a sucker. This might be due to a damaged rootstock or cutting the rose back too far.

This type of growth must be removed or it will dominate the plant and squelch the growth from the good part of the plant. In fact, if this growth is that obvious, it should be removed anyway.

Trace this growth back to its point of origin and identify where the union is located. The union should be a swollen part of the plant that may resemble, in looks, like a gall or tumor but it is not.

If this strong growth is coming from this spot or below it, remove it as close to the parent plant as possible. I would wait now and do that next winter.

Q: My husband planted my daffodil bulbs too close together, and now I need to thin them out. I need to know when it is the best time to do so.

A: Probably not a good idea to move them now if you have seen new growth from the bulbs. New growth will mean they have sent down roots. You could discard them anytime.

Moving them now could mean a lot of root damage to the plant and at a time when we are entering hot weather. It is best to wait until you see leaf dieback after flowering to move them.

Q: Do we have woodpeckers in Las Vegas? I have holes in the trunk on the north side of my carob tree. The trunk is 5 to 6 inches in diameter. I saw a bird perched there apparently pecking and went out to see if there were ants.

A: We have sapsuckers in the Las Vegas area that invade home landscapes this time of year. They create quarter-inch holes in tree trunks in a nice, neat row or rows — almost looks like someone drilled them.

About the only thing you can do is to restrict their access to the trunk or large limbs with a barrier of some sort. I have had fruit trees with this kind of damage that do well for many years.

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