Tuesday | June 28, 2016
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Caterpillars crawl on orange tree

Recently I picked three caterpillars from my orange tree. Two were about 1 1/2 inches long and the other was half that size. They are bright green with articulated bodies. They have eyes on the top of the second or third portion of the bodies and white lacy-looking marks along their sides just above the legs. I was going to bring them to your last class but then the two larger ones cocooned, bright green, hung on leaves. The smaller one is still eating and growing. Do you have any idea what they might be? J.G.

There are a few different caterpillars that feed on orange trees, as well as other citrus. One in particular is the Asian or Chinese Yellow Swallowtail, (Papilio xuthus). The adult is a mid- to large-sized swallowtail butterfly which is also found in Northeast Asia, Korea and Japan. It is sometimes called the citrus swallowtail.

No matter which caterpillar it is, they are under good biological control, and a mature citrus tree can tolerate certain damage. If these pests are attacking a young tree and are consuming numerous leaves, a Bt (Bacills thuringiensis) spray is warranted, and will do a good job. Spray in the late afternoon.

Dear Mr. Sakovich, I live in downtown Hilo and am trying out a Garden Tower for vegetables and herbs. About two weeks ago, I noticed something growing on a chard seedling. When touched or sprayed with water, a fine brown powder flew up. I’m guessing that it’s some sort of fungus, but it doesn’t seem to be on anything else in the vicinity. Can you tell what this is and how I can treat it? Enjoying your column very much. Mahalo, L.S.

You are right, it is a fungus. In fact, this fungus is a type of mushroom called a puffball. The name is in reference to the way the spores are disseminated. As you described when pressure is exerted from the outside, as from raindrops or a small animal passing by, the multitude of spores inside burst out like a puff of dark smoke. Most puffballs are small like a marble or golf ball. But there is one, the giant puffball (Calvatia) which measures 1 foot in diameter.

Puffballs feed on organic matter, often times living in the soil on the remains of trees that have been cut down. They are not plant pathogens; no treatment is necessary. Most puffballs are edible and larger ones are sold in some markets.

Caution: some puffballs, however, are poisonous. Do not eat any puffballs or other mushrooms that come up in the garden!

I’ve done a lot of traveling and have noticed in some regions the rinds of citrus are fairly thick. While in other areas they are so thin it’s hard to peel. Can you tell me what causes such a variation? M.

There are two main factors that influence peel thickness in citrus: nutrition (the N-P-K content in the leaves) and humidity. Fruit grown in humid areas like Hawaii and Florida have a thinner peel than those grown in arid climates like California and Arizona where the peels would tend to be thicker.

In addition, trees with higher concentrations of nitrogen in their leaves tend to have thicker peels. Trees deficient in phosphate will produce fruit with thick rinds.

Higher levels of phosphate in leaves tend to reduce the thickness. Trees with excess amount of potassium are inclined to produce fruit with a thick, rough peel.

Conversely, trees with low potassium produce fruit with a thin peel.

Class Announcement

I will be repeating my gardening class Common Pests of the Garden & How to Control Them at the University of Hawaii at Hilo. By request, the class will be on a Sunday afternoon, from 2-5 p.m. on Sept. 15, in order to accommodate those with busy schedules. We will look at many of the widespread diseases and insect pests that attack garden plants. Call 974-7664 to register, or go online at http://hilo.hawaii.edu/academics/ccecs/fitness/. There is a fee.

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 askthegardenguy@earthlink.net.


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