Friday | April 24, 2015
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Strange scale insect can infest variety of plants

I have a number of coleus plants in my garden that are covered with peculiar looking white insects (see photo). They don’t fly so I don’t think they are white flies. How can I get rid of them?

We have had this question before; it is indeed a strange creature. The pest is a scale insect called greenhouse orthezia, also known as ensign scale, lantana bug, Maui blight, and others. The bulk of the insect that you see, the larger white part, is actually a thick waxy ovisac that is attached to the insect’s abdomen. Eggs hatch inside this ovisac, and tiny new scale insects emerge.

This pest will infest a wide range of plants from mosses and fungi to grasses, woody shrubs and even small herbaceous plants. In Hawaii it is most commonly found on lantana and coleus.

Orthezia damage their host by feeding on the phloem tissue and at the same time excreting nutrients (honeydew) which promotes the growth of sooty mold.

Biological control: A coccinellid predator beetle (Hyperaspis pantherina) has proven successful in controlling this scale insect in certain areas. But at times, especially on coleus, the orthezia scale can get out of control. Effective chemical treatment has not been documented, but a thorough spraying of an insecticidal soap or a horticultural oil may be successful. On the positive side, orthezia scale itself has been used as a biological control agent of the invasive lantana shrub.

I have a Ficus retusa tree on my property. A portion of the leaves are always folded together and spotty. It has been like that for a long time now. It doesn’t seem to be killing the tree, but I’m afraid to lose it, it’s very beautiful. Can you help? G. in HPP

This damage is fairly easy to identify, it is quite distinct. The injury is caused by an infestation of an insect called Cuban laural thrips.

They attack only a few species of Ficus, notably the retusa, while most others are immune. But when thrips become abundant, they will feed on other hosts.

Using their rasping, sucking mouthparts, they feed on the tender, light green leaves causing a sunken purplish red spotting. As the thrips feed, the individual leaves roll together with the thrips inside. Eventually, the feeding causes a yellowing of the leaf along with some dark spotting.

In the wind and rain, these leaves will ultimately drop off.

With small trees, regular pruning of infested branches is often effective. However, shearing off a few inches like trimming a hedge should be avoided. This will stimulate new growth which is then susceptible to attack. Folded leaves can be unsightly, but rarely become serious.

In most cases the thrips can be ignored. If treatment is needed, common contact insecticides are of little use since the thrips are rolled up inside the leaf. Using a systemic insecticide like acephate would be more effective.

I have some fruit developing on my breadfruit tree for the first time. How can I tell when to pick it?

Breadfruit is abundant in Hawaii from roughly July to February. Fruit is picked when mature, which is indicated by the appearance of small drops of white latex on the surface. Breadfruit can be eaten before it is ripe, as a vegetable, or eaten as a fruit when it ripens. For the former, it is picked while still starchy and is boiled or roasted. Fully ripe fruit are sweeter, soft to the touch with a sweet, aromatic smell and often baked whole. The seeds are boiled, steamed, roasted and eaten with salt. The leaves are eaten by domestic livestock.

Breadfruit is high in carbohydrates and a good source of fiber, vitamins and minerals. The trees are relatively free of pests and insects; fruit flies will infest ripe fruit.

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. Also, visit his website at www.gardenguyhawaii.com.

 

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