I found several references to insects when Googling this. Below from
Ron Smith, Horticulturist, NDSU Extension Service Q: I have a jade plant that has a hard, brown layering on top of the leaf and wraps slightly around the bottom of the leaf closest to the stem. The layering has about the same texture as the jade bark/stem. It started in late fall and seems to affect the new leaves at the top of the plant, but the rest of the plant is infested as well. Can you tell me what it is and how to treat it? (e-mail reference)
A: Scale insects are difficult to control. There are several remedies that can be tried in an attempt to eliminate scales from a houseplant. However, there is no easy, simple cure. One possibility is to pick off individual scales or gently scrub (or rub) the scales loose from the leaves and stems. This is a labor-intensive task that only works on small, large-leafed plants. Dabbing each scale with an alcohol-soaked cotton swab is another possibility on lightly infested plants. Insecticidal sprays have limited utility. Their effectiveness is related to how well the material is applied and the duration of the particular insecticide. Try an insecticidal soap to see if that works.
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From
thegardenhelper.com There are several types of brown spots that can occur on the leaves of a Jade plant. If the brown spots are soft, it is caused by leaf spot disease. To control it...water with a systemic fungicide and improve the ventilation. If the brown spots are dry, it is caused by underwatering. Jade plants require generous amounts of water in the summer.
Sooty Mould is another spot that can occur. It is a black fungus which grows on the sticky honeydew depostited by aphids, scale, whitefly and mealybugs. This mould does not harm the plant, but will reduce the growth and vigour. It will block the pores. To remove it wipe the leaves with a damp cloth and rinse with clean warm water. Make sure (if there are insects) you control them.
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From
University of British Columbia Botanical Garden -
From this site with lots of useful info:
http://www.mobot.org/gardeninghelp/h...ges/3758.shtml "... leaf shiners or oils should never be applied to jade plants.
The principal pests of jade plants are mealybug, red spider mite, scale, thrips, and occasionally, aphids. Some succulents are sensitive to certain insecticides. Before you embark on a spray program be sure the product you use is labeled for jade plants."
Here's the recommendation from this site on how to treat.
http://www.npr.org/programs/ta...116.html#scale "If the scale is on the leaves, pick the leaves off and throw them away (even if this means denuding the plant). If the scale is on the stems, try suffocating the scale w/rubbing alcohol. Dip a cotton swab in the alcohol and apply to the scale, holding it there for thirty seconds (that oughta do it).
Make sure the plant is away from vents, drafts, central heating, etc. and keep it consistently watered (waiting each time until the surface soil is dry)."
