Make sure to follow directions when using insecticides

Advertisement

uestion: I have some type of white powdery bug on my climbing fig. The smaller leaves are dying. There are a lot of lizards that live in this foliage and I am reluctant to spray insecticide on it, because I don't want to kill them. What do you think could help? By the way, the vine is about 20 years old.

Answer: You might want to try some Neem insecticide, which is a botanical made from the Neem tree. You have to apply it when temperatures are below 90 degrees Fahrenheit and will stay there for several hours, although recently I applied it to several types of fruit trees experimentally when temperatures were over 90F and later that day hit 110F with no problems.

I would apply it very early in the morning; the earlier the better. Neem is safe for your lizards.

Q: All of a sudden my peach tree leaves are yellowing, curling and falling off. There also are dark brown spot under the leaves. I have been watering daily, since my sprinkler system recently failed.

A: There could be several things that could be going on. I am not sure if this is a life-threatening event for the peach, but watering every day might put it over the edge.

Tell me how old the tree is; whether it is big, medium or small sized; the kind of peach or when it bears fruit if you know; how much sun it gets and if it is planted close to a wall; if it is in bare soil and nothing on top of the soil (mulch), or if it is in rock mulch or wood mulch; whether all the leaves are dropping or just some of them. Are the branches still supple, or do they break when you bend them a bit?

The dark spots may mean nothing. However leaves yellowing and dropping off can mean a lack of water (drought) or too much water (root rot). The variety of peach do drop some of their leaves after fruiting and regrow new ones at the end of the branches in midsummer. An example is a peach called Fairtime.

Boring insects in the trunk and limbs can cause leaf death and drop and branch death. Borers usually attack single limbs of larger trees and the trunk itself in smaller trees. This is particularly true if the trunk is damaged by the sun (sunscald). You might also see sap oozing from infested branches in later stages of attack.

If you see this then you might want to cut dead areas of bark away from the trunk to healthy wood. The borer will not be in the dead parts but in living parts of the tree bordering the dead areas.

If it is due to overwatering, the tree will be loose in the ground when you move it since the roots are rotting. If there is wood mulch around the trunk, keeping it wet would cause what is called collar rot, or rotting of the trunk. This would cause the entire tree to suddenly turn brown, drop leaves and die, particularly when it is hot. Pull any mulch away from the trunk a few inches if it is too close.

But one day of no water, when the tree really needs it, can be enough to cause leaf drop. Leaves will grow back when water is reapplied. Watering every other day would be adequate provided it is not recently planted.

Fertilizing too close to the trunk can burn the trunk and cause leaf burning or leaf drop and possibly death. But this would be within a few days after the fertilizer is applied. Spraying the tree with an oil-based pesticide during the heat might cause leaf drop. Drift of a weed killer from a neighbor can cause leaf drop. Surrounding the tree with rock mulch can cause leaf drop. Converting a tree from sprinklers or bubblers to drip and not getting the watering times and amounts correct and spacing and number of emitters can cause this as well.

There are no diseases this time of year to worry about. But certainly the heat and high light intensity are prime suspects as well. There really is not much you can do at this point if borers are not found. Wait to see if you see any new growth from the ends of the branches.

Q: I have five, 10-year-old rose bushes that in the past have bloomed every year. They all seem to be doing very well except for one two-toned rose bush. I feed and water them the same but the two-toned rose isn't looking too good. Can you suggest a remedy?

A: From your description it is really tough to tell without more information. For instance I don't really know what you mean by not doing very well. Roses do not do well in rock mulch. They like organic mulches.

They don't do well in a southern or western exposure during the summer. They do recover in the fall and spring, but go bad in the summer due to the excessive heat and lack of humidity. They should be fertilized three or four times a year and need to be pruned appropriately which is difficult to explain via e-mail or whether that is really the problem.

These plants are getting old. They do have an expected life span after which they probably should be replaced. Yours are approaching that now. You might want to consider replacing them over the next few years. Make sure they are planted in areas with some protection from intense sunlight and make sure they are mulched with organic mulches.

Q: Last November I transplanted two canary palms in my backyard from my office building, where they had thrived for several years. They proceeded to go into deep shock, and the existing fronds dried out and died. I found that the heart was still green, having consulted with two separate landscape companies. Here we are in the summer and one is showing some strong frond growth from the heart, while the other seems to be struggling. I have had conflicting advice, depending upon the source -- lots of water, cut back on the water, use this food, make sure the root ball is uncovered. The latest product I have tried was Super Thrive, which I sprayed on today, as I have heard from several sources about its wondrous abilities. I know these trees are quite valuable and I do not want to lose them. What can you recommend? Should I bring in an expert?

A: You don't need an expert. November is the worst possible time to transplant palms. They frequently struggle the following year and have a good chance of not making it. They transplant best during the heat of the summer, unlike many other plants.

All you can do at this time is to not over water. Hopefully you replanted them at the same depth they were at your office building. I would expect some fronds to die when transplanting. That would be normal. It's the center fronds that are important now. If the center bunch of fronds dies then the palm is dead.

Water them deeply and infrequently. Once a week is plenty to a depth of the root ball. No special fertilizer is necessary at transplanting time, provided they came from a nursery. All the nutrients are in the trunk for rejuvenating the root system. If they have been neglected in the past then they will need a fertilizer applied such as a 20-20-20 or tree stake fertilizers at planting time. However, fertilizing them at planting time will not damage them if applied lightly.

Q: Can a bird of paradise plant thrive in our desert climate? I noticed at a nursery that they have bird of paradise for the outside and also for house plants. How about horsetails? Is it best to plant a horsetail plant in the ground outside or in a pot outside?

A: When you are talking about bird of paradise, I am assuming you mean the African bird of paradise, not Mexican which is a desert-adapted plant. I grew African bird of paradise here for many years until I lost it to extreme cold at the turn of the millennium.

It will need a lot of soil modification in the root zone with good quality amendments and protection from direct sunlight such as a northern exposure that gets lots of indirect light and no late afternoon direct sun which can happen in some northern exposures here.

The other possibility would be filtered sunlight all day long such as shade from a tree. I am not sure whether it can handle any direct sunlight even in the early mornings. If it does, it would have to be very early morning sun when it is cooler and less intense.

You will have to protect it from winter cold in case it freezes. It will not handle any frost but if it does get nipped lightly or even burned down due to cold, it will come back from the ground if mulched. Mulch with three to four inches of good compost or wood mulch. Fertilize with a high quality interior plant food like Peters, Miracle Gro or Miracid.

Horsetail is terribly invasive if it gets into a wet area but can add some nice verticality to a landscape planting. It has a plant texture hard to match with other plants. You should double-pot them in the landscape unless the area is totally surrounded by dry soil and you can contain them.

Put a layer of gravel in the bottom of the outside pot so that the two pots do not lodge together. The outside pot should not have drainage holes located where horsetail can go through the holes of the interior pot and then again through the holes of the exterior pot and finally into the ground. It will do that if given a chance. Watch out for that plant!

Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.