Friday | July 29, 2016
About Us | Contact | Subscribe

Garden Guy: With proper care, a citrus tree can live a long life

Dear Garden Guy, I have an old citrus tree in the front yard that I really don’t take care of and I’m thinking of having it removed, but my hesitation is that it still produces some “OK” fruit.

There are a lot of dead branches and on the trunk are big grey blotches and moss, too. Ants are a problem. I’m not sure it is worth saving, it may be too old. Any thoughts?

First, assuming that the tree has no major diseases, the “old age” and neglect aspect, along with lichens (grey blotches) and insects can be remedied. Unless a tree succumbs to disease or the bulldozer, citrus can live up to 60 or even 100 years.

1. Start with some heavy pruning. Take out all the dead wood, branches that cross and suckers coming up through the tree. Then prune to open up the tree, allowing more light to penetrate to the interior branches, thus more bloom and more fruit.

2. Apply a nitrogen fertilizer to the ground (phosphorus and potassium if the soil is deficient), then put down an organic mulch from the trunk to just beyond the dripline of the tree, or more. Don’t forget to leave an air gap between the trunk and the mulch. A mixture of wood chips and manure would be great. If the soil pH is too acidic, apply some lime before the mulch.

3. Ignore the lichens; it’s not harming the tree. Visit for a more detailed explanation of lichens and moss.

4. The presence of ants means there are insects in the tree. They can be of various types — whitefly, aphids as well as different kinds of scale insects. Visit for a more detailed explanation on ant control. With the ants gone, natural enemies

(biological control) will be able to come in and clean up the pest problem.

Alternatively, more than one application of horticultural oil should clean up the insects.

According to many gardeners, insect pests present the greatest challenge. You can find the answer for many common pests on my website. In this short space, however, I would like to give you a few guidelines to the question, “What’s causing that?”

First, inspect the plants; scrutinize them carefully, especially the underside of the leaves, using some type of magnification if necessary. Look for the insects themselves or their signs:

• Chewed leaves or blossoms could be caterpillars, beetles, sawflies, snails, or slugs.

• Tunneling or a trail in the leaf is leafminers.

• Stippled, bleached or yellowed leaves are caused by leafhoppers, aphids, lace bugs, phyllids, or mites.

• Distortion (twisting, cupping, swelling) of plant parts result from thrips, aphids, eriophyid mites, bud mites, psyllids, gallmakers, true bugs.

• Twigs dying back are a sign of twig borers, scales, or tip miners.

• Presence of excrement comes from lace bugs, plant bugs, thrips, or caterpillars.

• Sooty mold means the presence of aphids, soft scales or whitefly.

• Froth is caused by spittlebugs.

• A white, waxy material is evidence of aphids, mealybugs, adelgids, or whiteflies.

An additional inspection should be carried out after sunset. This is when slugs, snails, Chinese Rose beetle and some caterpillars come out to feed.

When you have found something, go to the literature for identification. Check the University of Hawaii College of Tropical Agriculture and Human Resources website and click on “Knowledge Master.” Look for, Information on agricultural crops. Also go to the University of California IPM website,, and click on “Home, Garden, Turf, and Landscape Pests.”

Here you will find good information on pests in addition to some excellent photos.


The different shapes of papayas are due to the three different types of trees.

1. There are female plants that produce only female flowers. These contain an ovary for fruit production.

2. Male plants which produce male flowers, containing only pollen.

3. The “hermaphroditic” plants which contain only hermaphroditic flowers. That is, flowers which contain both ovary and pollen and can pollinate each other, called self-pollinating.

The female trees must be pollinated in order for fruit to mature. This fruit is a medium to large, round-shaped fruit of good eating quality and a large seed cavity. Unpollinated female flowers develop small fruit, which drop to the ground. Male flowers rarely form fruit. Hermaphroditic plants consistently produce small to medium, elongated to pear- shaped fruit also of good quality with a smaller seed cavity.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at Also, visit his website at


Rules for posting comments