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Q

I've always heard that Japanese beetles prefer purple-leaved plants to green-leaved plants. Is this true? — South Carolina

A

While it would appear sometimes that Japanese beetles prefer purple-leaved plants, this is not always the case. A study that looked at beetles' choices of 12 species of woody landscape plants and several cultivars found quite mixed results. Even though the beetles preferred purple Norway maples over green ones, they did not prefer purple Cotinus or Fagus better than green. Often, they preferred green-leaved plants over their purple-leaved cultivars.

SLIDING SCALE

Q

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What can you tell me about Florida wax scale? I think I have an infestation on my Burford hollies. — Via the Internet

A

Florida wax scale is a serious pest on all types of hollies, maple, citrus, Indian hawthorne and other ornamental plants. As with other scale insects, the wax scale secretes a waxy coating that protects it from some predators as well as from insecticides. The Florida wax scale is wet-looking and a whitish-pink color; the plant may also have black sooty mold, which is a fungus that lives off the honeydew secreted by the scales. There may be two to three generations per year, depending on where you live, with the first emergence typically in late April to early May. Some scales live only on stems or leaves of the plant, while Florida wax scales can be found on all above ground parts of the plant. They remove large quantities of sap with their piercing-sucking mouthpart. The scales you see may either contain eggs waiting to hatch or nymphs or adults settling in to feed.

Scale infestations are difficult to control but not impossible. Horticultural oils in combination with systemic insecticides have been successful. Target your spray applications when the eggs have just hatched into crawlers and are most susceptible to insecticides because they have not yet formed their protective coating and are wandering the plant for a place to live. A study performed back in 2001 found that I. aquifolium, I. cornuta, I x meservae and I. opaca were among the most heavily infested. Least infested by Florida wax scale were I. crenata, I. glabra, I. verticillata and I. vomitoria. Your control may include removing the Burford hollies (Ilex cornuta ‘Burfordii’) and replacing them with one of the other, less susceptible hollies.

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