In about 6 weeks it will be time to spray the magnolia scale. In the past, I’ve used insecticidal soap or neem on scale. I wonder what would be best to control this pest.
I also plan to include the magnolias on the dormant oil spray roster from now on.
Pesticides labeled to kill Magnolia scale include:
Chlorantraniliprole
Chlorpyrifos
Malathion
If you are going organic, oil works well when temps aren’t too hot to use it. Best to control them in spring and to use at least 2% hort oil. Make sure the whole plant is saturated. The chemical I use is Centaur along with oil, but oil should be enough. Centaur is only packaged in a scale for commercial growers or applicators.
I hate scale.
That’s my plan for spring, before the leaves come out. I think that’s the best time to attack scale. But I read that the scale would be vulnerable in late August, when the newly-hatched crawlers emerge
If you get some cool weather, hort oil works find in late Aug. I used to control scale at a site where we only did a petal-fall and one more spray 10-14 days later and got control of terrible scab.
I don’t use oil if predicted temps are above 85F.
You would say hort oil instead of neem, then
I’m unaware of research on the efficacy of neem and have never used it. If it worked for you I would expect you to trust it for the purpose. The oil is less environmentally disruptive, I think. It evaporates quickly and only kills what can’t leave the tree easily.
Neither work here.
You mean in your experience or based on experimental data? Hard to see how they could survive suffocation there. Timing is everything, as I realize you know but oil is considered an effective suppressant here and spring application has suppressed it for a whole season here at several sites I’ve managed over the years. .
Here’s what UC Davis says,
Monitor for San Jose scale during the dormant period by checking prunings to make sure scale hasn’t developed in tree tops. Also check fruit at harvest for the presence of scale.
Due to the damage potential of this pest, annual dormant sprays are recommended in most areas. Oil sprays work the best on the black cap stage, so apply them in early January. Control heavy populations of San Jose scale by applying an insecticide plus oil spray during the delayed dormant period.
If inadequate control is achieved with the dormant spray, treatments are also effective when applied soon after the emergence of the crawlers in May. Use pheromone traps in March to monitor for male San Jose scale flights and double-sided sticky tape for monitoring crawlers in April and May. Time a treatment, using a 51°F lower threshold and 90°F upper threshold, for 600 to 700 DD after the beginning of the male flight or 200 degree-days after crawler emergence begins.
I’ve never tried controlling scale on magnolias, so maybe that’s a different ball game than San Jose scale on apples.
Magnolia scale (Neolecanium cornuparvum) can be virulent in the southern California environment.
Barnicle scales (Ceroplastes sp.) are another tough one here.
Yeah, I’m not sure oil would work for peach scale either- the scale shows up shortly after oil apps apparently as I’m seeing it on trees that were supposed to receive oil spray. I like Centaur, a new lower risk material that is also more species specific than something like Lorsban. For one of the new formulas a bag isn’t TOO expensive.
If course, if you keep repeating oil apps you can sometimes (usually?) get results, as long as it is when scale are vulnerable.
I’ve just used it on the brown scale on potted citrus