Use of Neem oil on C. japonica

bubba62January 6, 2008

I'm considering applying Neem oil to several camellias which are chronically infested with tea scale, but there's a caution on the bottle that it may cause foliar damage and should be tested first on a few leaves. Anybody have experience with this, or perhaps a better way of dealing with a nasty scale infestation? I've tried lots of things already, including sunspray oil, malathion, and a systemic insecticide; the latter two are products of last resort for me.

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luis_pr(7b/8a Hurst, TX)

From the American Camellia Website: "Control of Scale: Scale infestations are more difficult to control when populations are heavy. Homeowners should make spray applications when the first sign of scale is seen. Oil emulsion sprays will give effective control if applied properly. This is a contact insecticide. For it to be effective, the plants must be thoroughly covered (top/bottom of leaves). Oil emulsion sprays should be applied only during the spring and fall when the temperature is 40 - 85° F. Spraying in the heat of the day may result in burning the leaves. As a general rule, apply no more than three times per year with at least 60 days in between sprays. Oils are compatible with other insecticides."

From Clemson University: "Controls: With a light infestation, scales can be scraped off the plant and discarded. If only a few leaves are infested, hand picking and destruction of infested leaves is very effective. The best time to spray with a refined horticultural oil (Bonide All Season Spray Oil, Ferti-lome Scalecide, Green Light Horticultural Oil Spray, or Ortho Volck Oil Spray) is in spring, after the plants have finished blooming and the danger of cold weather has passed. This will kill many adults, crawlers and eggs by smothering them. Spray two applications, 10 days apart. Spray when temperature are between 40 and 85 degrees.

Most insecticides are effective only against the crawlers. In addition, using an insecticide against scales can result in the deaths of naturally occurring enemies of scales. As such, insecticides should be avoided unless the camellia is very valuable.

Monitor the crawler emergence with sticky cards, tape wrapped around a branch, or by putting an infested shoot or leaf into a baggie and watching for crawler movement. Crawler activity often coincides with the flush of new plant growth in the spring. However, some scale species may have overlapping generations with an extended crawler emergence period, such as along the coast.

Insecticides labeled for homeowner use against tea scale crawlers include acephate (Ortho Japanese Beetle Killer), malathion (Ferti-lome Mal-A-Cide, or Hi-Yield Malathion Insect Spray), cyfluthrin (Bayer Advanced Garden Power Force Multi-Insect Killer), and carbaryl (Sevin 50WP or Ferti-lome Carbaryl Spray). As with all pesticides, read and follow all label instructions and precautions."

    Bookmark   January 6, 2008 at 9:57PM
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rhizo_1 (North AL) zone 7

bubba, the warnings about neem are for the same reasons as with non-neem oils. If you follow the directions regarding temperatures, you should have no problem with the neem. This is probably not the ideal time of year to be making oil applications.

Be sure to spray the neem on both surfaces of the leaves to obtain the best results from your efforts. Neem's effects are somewhat systemic, but you still want thorough coverage. Repeat applications, of course, will be necessary. That's true for whatever product you use.

I have been very pleased with neem oil. I use no chemical pesticides at all, and this has been very helpful for that rare outbreak of mites, aphids, whitefly, or scale.

    Bookmark   January 9, 2008 at 8:55AM
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Thanks, rhizo-

I actually went ahead and gave it a shot on several badly infested plants. Nothing to lose, in these cases, and we've had weather pretty consistently within the recommended temp ranges for the last week, with not much change expected. Not good news for my cypripediums and tree peonies, which need a good, solid dormancy, but the temperate plants are loving it. Anyway, we'll see what happens re. the neem appilications.

    Bookmark   January 10, 2008 at 5:05AM
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