Some branches may produce inferior fruit

Dear Garden Guy, I have an orange tree in my front yard. One of the branches is very vigorous, has large thorns on it, and the fruit was very sour.

Why is this branch different from the rest of the tree? Thanx, E.N.

The vigorous shoot, or branch, originates from the rootstock, and therefore, is not genetically part of the grafted orange variety. Rootstocks are chosen because they possess resistance to disease or some other cultural quality desired by the grower. The fruit borne from the rootstock, although a citrus species, is often sour, bitter and with little juice. Occasionally a bud will break from the rootstock, develop into a branch and grow up through the tree.

Eventually, this branch can set fruit, but as noted, usually of inferior quality. These sprouts or branches should be cut out. Since they are usually more vigorous than the grafted portion, if not removed, they could eventually dominate the entire tree.

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I saw plum trees for sale at Walmart. I don’t remember what cultivar. Are there any plums that fruit in Hilo or are those destined for higher elevations?

There are some varieties of deciduous fruit trees that will grow and fruit in Hawaii. The yields will not be comparable to those of colder climates, but the trees will produce fruit, the higher the elevation, the better. The area around Volcano Village has produced good fruit from deciduous trees. The key is the number of hours below 45 degrees F (chilling requirement).

The normal 500-1,000 hours required does not work in the tropics! Yet there are now low chill varieties which are rated at 150-250 hours. These are the ones to buy for Hawaii.

Know the “chilling requirement” of the variety you wish to plant. See my website www.gardenguyhawaii.com and search deciduous for a more detailed article.

Paradise Plants in Hilo may have available deciduous trees left from their January/February.

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New Pest for

Backyard

Avocados

Originating in Mexico, the Persea mite, Oligonychus perseae, was found in California in the early 1990s and probably came to the Big Island in the early 2000s. The main host for the mites is avocados. Some varieties are more susceptible than others; the Lamb Haas is considered least susceptible. Adult mites have eight legs and an oval body, with two dark reddish eyespots near the head end of the body. They lack antennae and body segmentation.

Mites feed both on the fruit and leaves, most notably on the underside of leaves.

The damage appears as small, circular, yellow to brown spots. Mite colonies often reside against the protruding midrib vein of the underside of the leaves. They produce a dense, silk webbing of protection over them. The webbing resembles a silvery spot on the underside of the leaf, often seen glistening under sunlight.

Once the feeding damage to the leaves reaches and exceeds 10 percent of the surface area, premature leaf drop begins. This can lead to sunburned bark and fruit; yields have been reduced up to 20 percent. Trees will recover from the defoliation by producing a new flush. But repeated dropping of the foliage will severely stress the tree.

In the home garden, some mites can be tolerated. Several species of natural enemies often reduce the population of the mites. If numbers get too high, horticultural oils will suppress the mite population. The spray must contact the undersides of leaves, where mites are located. Where feasible, spraying the underside of the leaves with a forceful stream of water can also reduce mite populations. Whitewashing, using hydrated lime or diluted white latex paint on the trunk and major limbs, will help protect bark and wood from sunburn after premature leaf drop.

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.