1
Citrus General Discussion / Winter, indoor citrus, mites, and UV
« on: March 03, 2024, 10:12:07 PM »
I've always noticed that in the summer, when the trees are outside, I never have issues with mites. I considered that the rain kept the population low but I noticed I would still have mite issues inside (or this year, in a greenhouse) that would start in Jan/Feb even when I would spray the trees with water, soap, or oils.
The timing was puzzling. Mite populations can reproduce quickly (one search says 8.5x in 10 days) yet it took 3-4 inside months before suddenly requiring back-to-back-to-back-to-back endless spraying regimens.
So why absolutely no issues outside with no regimen, but a delayed issue inside?
Two interesting papers that highlight the effect of UV both as a) a direct suppressor of mite populations and, more interestingly, as b) a catalyst for defensive citrus resistance to mites.
This is slightly problematic for greenhouses with UV-blocking polycarbonate! But perhaps there is a time lag after UV is reduced (for example, when plants are moved inside) where the mite-preventing volatiles are still produced within the plant.
Deleterious Effects of Uv-B Radiation on Herbivorous Spider Mites: They Can Avoid It by Remaining on Lower Leaf Surfaces
UV-induced citrus resistance to spider mites (Tetranychus urticae)
The timing was puzzling. Mite populations can reproduce quickly (one search says 8.5x in 10 days) yet it took 3-4 inside months before suddenly requiring back-to-back-to-back-to-back endless spraying regimens.
So why absolutely no issues outside with no regimen, but a delayed issue inside?
Two interesting papers that highlight the effect of UV both as a) a direct suppressor of mite populations and, more interestingly, as b) a catalyst for defensive citrus resistance to mites.
This is slightly problematic for greenhouses with UV-blocking polycarbonate! But perhaps there is a time lag after UV is reduced (for example, when plants are moved inside) where the mite-preventing volatiles are still produced within the plant.
Deleterious Effects of Uv-B Radiation on Herbivorous Spider Mites: They Can Avoid It by Remaining on Lower Leaf Surfaces
UV-induced citrus resistance to spider mites (Tetranychus urticae)
- "Abundances of Tetranychus urticae on Citrus exposed to solar UV decrease compared to seedlings under UV filtered radiation."
- "Mite induced plant mediated resistance is dependent on exposure to UV radiation."