Alternative control methods


Start with clean plant material.This will help prevent scale problems, and removal or chemical spot treatment of heavily infested plants will reduce the spread of crawlers to adjacent plants.

Chemical control

Spot treatments should be applied when less than half of the crawlers present are parasitized and the infestation is spreading. Use insecticidal soap or horticultural oil if no predators or parasites are present; these treatments will kill exposed natural enemies.

Insect growth regulators are registered for use on ornamentals for control of armored scales and other insects as a preventative treatment. These can be used when parasites or predators are present.They do not affect natural enemies but may damage some plants. Azadirachtin (several brands) can also be used.This insect growth regulator is a commercial formulation of neem seed extract.

Possibilities for effective biological control

Selected species of armored scales should be susceptible to biological control using Aphytis melinus and/or lady beetles. If your greenhouse crop is infested with an armored scale, try introducing these natural enemies to find whether they will control it. No research has been conducted on wasp release rates for armored scales in greenhouses (three applications at a rate of one wasp per ft2 is suggested for outdoor use), but it has been suggested that procedures similar to those for the soft scale parasite Metaphycus helvolus be used. The wasps will disperse readily from the release site.You can release wasps by opening the container and allowing them to fly out as you walk through the greenhouse.

Suggested release rates for lady beetles, such as R. lophanthae,are four to six beetles per 10 ft2 for light infestations, and slightly more for heavy infestations. Make two releases about 3 weeks apart.

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