Sunlight damaged limbs more prone to borer attack

Q: I was checking today after our big rain and noticed something weird low on the trunk of my peach tree. I touched this spot and a chunk of rotten wood came off. Was this an unnoticed borer attack or something to do with the rain? Can it be fixed?

A: Trees in good health recover from damage quickly, particularly when they’re young. Recovery depends on the extensiveness of the damage and tree health. Remove any loose bark and let this wound heal on its own without tree paint or anything added.

A great time to look for active borers in fruit trees is right after a rain. If there are borers active, you usually see a dark, reddish-brown jellylike ooze coming from the trunk or limbs. If I see this, I like to remove the damaged area down to healthy wood with a sharp, sanitized knife.

If you don’t see any oozing, then there are no borers present or the borers are not active. It’s possible it is old damage and the borers are gone. It is also possible it could be damage from something else.

Check to see if this damage is in a location where damage from borers is common. Locations for borer damage are commonly on upper surfaces of limbs exposed to direct sunlight and trunks or limbs facing west or south.

This is because borer damage is frequently found along with damage from intense sunlight or sunburn. If sunlight damages the top of limbs, then these damaged upper surfaces are more prone to attacks by borers than sides or the bottoms of limbs.

Sides of limbs or trunk facing south or west are more commonly attacked by borers than sides facing east or north. Again, this is because of damage by intense sunlight.

If trees are growing in a lawn or surrounded by weeds, damage to the trunk could be from a lawnmower or line trimmer rather than borers. Look to see if damage is at a height that could correspond to damage caused by a mower or line trimmer.

Make sure no weeds or grass grow within 3 feet of the trunk. Grass or weeds growing close to a tree should be dug out and replaced with wood chip mulch. This helps eliminate damage from mowers or line trimmers and reduces the number of pests that make it through the winter.

Another alternative is to lay old carpeting with woven backing on top of the soil surrounding the tree. This layer of carpeting smothers plants growing too close to the tree but allows air and water movement through it. If lawn mowers or line trimmers are used, they should always be kept away from the trunk.

Q: I have pomegranates that are a few years old. Every year they don’t produce flowers until late in the season when everyone is harvesting fruit. I am considering every option including removal of the plants.

A: Pomegranates produce flowers on new growth in late spring when many other fruit trees have already flowered. Pomegranates are slow starters in the spring but once they start flowering they continue to flower through most of the summer and year after year.

The balance between root and top growth affects flowering. The tree adjusts growth above ground to match growth and the size of its roots below ground. This root-to-shoot ratio affects flowering and fruiting.

If the top of the plant is cut back severely or damaged and the roots stay the same size, the top part of the plant grows rapidly and won’t produce flowers until the growth above ground again matches growth below ground. This ideal root-to-shoot ratio varies among plants, between species of plants and even among varieties.

I believe you are seeing a flush of rapid growth in the spring either because of loss of growth above ground. The top produces a lot of new growth at the expense of flowering. Flowering begins when that ideal root-to-shoot ratio is achieved again.

If you are pruning this pomegranate, do not prune it severely. If you are losing the size of the top because of freezing damage or mechanical injury, try to protect it. If this tree can maintain its root-to-shoot ratio from one year to the next, this problem will stop.

There is a difference in tolerance to freezing temperatures among varieties pomegranate. Some are more cold hardy than others. If winter cold damage occurs, it is possible your pomegranate is a different variety than your neighbors. The pomegranate variety Wonderful has been a solid performer in our climate.

Some pomegranates are “precocious,” meaning they flower and produce fruit at a young age but all of them should be flowering by the second or third year after planting. Some flower the first year after planting. Some flower possibly as late as the third year after planting.

If you can’t solve this problem through careful pruning, replace it with a fruit tree more cold hardy or suffers less from cold winter temperature damage.

Q: Two years ago, you correctly diagnosed our tomato plants with spider mites from pictures we sent. Last year we got spider mites again. We started most of our tomatoes from seed last year but bought a few plants from a local nursery and planted them in each of the vegetable beds. Is it common to get spider mites from nursery plants?

A: I don’t know how common it is for pests to be brought in from plant nurseries, but I know it is more common than I would like. I have personally witnessed and identified disease and insect problems coming from nursery plants (houseplants, transplants and landscape container plants) before they were planted.

Some plant problems are easy to see and others are not and don’t develop fully until later. Growing plants free of insect and disease problems requires knowledge about the pests, a clean growing area and a regular prevention and treatment program.

If possible, put plants in isolated areas until you are sure they are clean. This is a common recommendation when buying houseplants. Houseplants are frequently loaded with disease and insect problems and infest other plants once inside the house.

When bringing home plants, spray them with oils and soap and water before planting. Don’t bring home bargain bin or dumpster plants thinking you’ve got a deal. You are asking for trouble unless you know what you’re doing. Don’t risk contaminating pristine plants by mixing them with plants unknown to you.

As far as spider mites on tomatoes are concerned, inspect plants using the white paper method and a hand lens. Remove weeds growing in the containers, remove dying or damaged leaves, spray plants with soap sprays, and alternate with neem and other oils when you see them.

Q: Would you please give me your advice on pampas grass? I planted the grass in one area of my yard and it did not grow more than 3 feet tall. I moved it to an area which receives full sun a couple years ago. I believe I gave it the right amount of water and fertilizer. It doesn’t die out and it doesn’t grow taller than 3 feet or grow horizontally.

A: You did not mention if the pampas grass flowered or not. Flowering is a sign that it has reached maturity and won’t get any taller.

It sounds like you have a dwarf variety of pampas grass. They grow about 4 to 5 feet tall and no taller and about 3 feet wide. One variety from Monrovia Nursery is called Ivory Feathers and blooms in late summer or early fall.

A lack of water would show up as browning of the leaves and the plant would appear to be struggling. Pampas grass is very hardy in desert climates and should grow to their full height without any problems if they are getting enough water.

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

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