Rhodie problems - Ask Extension
HI, about 6 wks ago I came in w samples from a 50 yo rhodie. It had azalea lace bug (i do know how to identify already). The leaves were folded down, ...
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Rhodie problems #852382
Asked October 06, 2023, 12:49 PM EDT
HI, about 6 wks ago I came in w samples from a 50 yo rhodie. It had azalea lace bug (i do know how to identify already). The leaves were folded down, and the plant looked like it was dying. There was also this black 'soot', for lack of a better word. You said 2 other ppl came in similar samples, and this was not seen before. Later you identified it as a fungus, but unknown exactly what kind. I assume the fungus was killing the plant, as Azalea Lace Bug doesn't tend to? We cut it back, the wood is still alive. Thinned it out, gave it air circulation. Fingers crossed.
Nearby are 2 other similar age Rhodies, also big in the 12-15' range. I also thinned them quite abit, pruned excess afflected ALB leaves and have been spraying w Endall.
But now i'm noticing that black stuff. AND these white things. Ugh!
I've attached pics of both.
The good news the plant leaves haven't folded down. They look normal except for the ALB and these other 2 issues.
Do i need to be concerned about the black stuff? the white things?
Trying to hang onto these!
thank you
Donna
Lane County Oregon
Expert Response
The black is sooty mold growing on the excreta of the sucking insect. Unrelated to the lace bug. The pest is cottony scale.
Eggs hatch into crawlers, which are red with black legs and antennae. They settle along leaf veins and produce the white cottony secretion for which they are known.
Mechanical control: Scrape scale insects off plants by hand with fingernail or toothbrush. Prune off major infestations in trees and shrubs if possible. Apply tape, sticky side out or use a similar adhesive near infestations of adult scale to intercept and catch the crawler stage. Water landscape plants and trees properly, as drought-stressed plants are more susceptible to scale insects. Avoid excessive nitrogen applications as this encourages growth in scale insect populations. Generally, apply pesticide products to target the vulnerable crawler stage before the scale covering is formed. Management-biological control The waxy scale cover of these insects tends to conceal and protect them from generalized predators and from some pesticides. Numerous predators specialize in feeding on these protected scale insects including birds, lady beetle adults and larvae, mites and green lacewing larvae. Numerous species of minute wasps lay eggs in and parasitize scale insects. Biological control may prevent significant scale infestations. Avoid broad-spectrum insecticide applications that would disrupt these natural enemy populations allowing the scale to reproduce.
Eggs hatch into crawlers, which are red with black legs and antennae. They settle along leaf veins and produce the white cottony secretion for which they are known.
Mechanical control: Scrape scale insects off plants by hand with fingernail or toothbrush. Prune off major infestations in trees and shrubs if possible. Apply tape, sticky side out or use a similar adhesive near infestations of adult scale to intercept and catch the crawler stage. Water landscape plants and trees properly, as drought-stressed plants are more susceptible to scale insects. Avoid excessive nitrogen applications as this encourages growth in scale insect populations. Generally, apply pesticide products to target the vulnerable crawler stage before the scale covering is formed. Management-biological control The waxy scale cover of these insects tends to conceal and protect them from generalized predators and from some pesticides. Numerous predators specialize in feeding on these protected scale insects including birds, lady beetle adults and larvae, mites and green lacewing larvae. Numerous species of minute wasps lay eggs in and parasitize scale insects. Biological control may prevent significant scale infestations. Avoid broad-spectrum insecticide applications that would disrupt these natural enemy populations allowing the scale to reproduce.
