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Azalea & Rhododendron

spray for white fly after frost?

17 years ago

I am wondering if I should spraying my azaleas, which seem to have suffered from a white fly infestation in the summer. I sprayed them with Ortho Systemic Insect Killer about a month ago, and had considered spraying again, but we had a hard frost soon after so I wasn't sure if another spraying would do any good. Do the systemic insecticides work when the plant is dormant?

I am really concerned because these formerly gorgeous shrubs, which have been evergreen since I bought this house two years, ago are now losing their leaves. I had started seeing pale spots in September, but first thought the problem was an iron or acid deficiency since we had some masonry work done on the house. When testing revealed that this was not the problem, I bought a book on azaleas and saw the picture of white fly damage.

The book recommended the Acephate, but neither the book nor the directions on the label indicates whether I should continue the spraying over the winter. I hate using poisons in the garden since it kills all the beneficial insects as well as the nasty little sap suckers, but I'll do just about anything to avoid losing these shrubs.

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Comments (5)

morz8 - Washington Coast
17 years ago
Your description of the pest is missing something...if you had a white fly infestation heavy enough to be of concern, you should have noticed a literal cloud of tiny white moth-like bugs flying up when you brushed against the plants or disturbed them.

I wonder if your problem wasn't lace bug instead. The recommendation for lace bug is to spray when nymphs emerge, white fly - early spring or early fall.
wrighthouse
Original Author
17 years ago
You're right. I rechecked my book and the picture I recognized was for the lacebug infestation. But the recommended insecticide was the same.

Does this mean I need to wait until spring to spray again? Where do they lay their eggs? I've been doing the best I can to clean up the fallen leaves. What else can I do to help the shrubs recover? Should I prune back the bare branches or can I expect them to leaf out again in the spring?
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ego45
17 years ago
Couple of years ago I had a severe white fly infestation on one of large azaleas. I thoroughly sprayed it by horticultural oil in late fall and then again in early spring and never seen a single white fly (on azaleas) again.
Don't know about lacebugs though.
morz8 - Washington Coast
17 years ago
"Overwintering egg inserted into midrib on leaf underside" - so yes, good sanitation around your plants would be wise.

As for pruning, it might be a better plan to wait until Spring and see how the plants recover, do any cosmetic cutting back necessary then - you could still have a nice display of flowers even though you've had foliage damage.

I haven't had to treat lace bug myself (root weevils are our major azalea-rhododendron pest), possibly too cool here for them to become a problem? It varies a little from growing zone, but you shouldn't have any live lace bugs to indicate spraying after late August into September.

" Cultural Control - Planting Site Selection - Most lace bugs seem to prefer bright, sunny areas and are seldom a problem in shaded areas.

Cultural Control #2 - Use a hard jet of water from a hose to dislodge the young nymphs as they hatch in the spring (April/May). The tiny nymphs often die before they can find their way back to suitable leaves.

Biological Control - Naturally occurring green lacewings, mites and assassin bugs attack lace bugs.

Chemical Control - "Soft Pesticides" The insecticidal soaps are useful if contact with the nymphs is made. Be sure to cover the underside of the leaves where the nymphs are feeding. Additional applications may be needed to control nymphs hatching out of eggs laid late.

Chemical Control - Standard Insecticides acephate (Orthene) Make applications as soon as the eggs hatch in the spring (again, April/May). Monitor the plants and repeat applications if re-infestations occur. "
wrighthouse
Original Author
17 years ago
Thanks, I'll keep vacuming up the leaves--a new use for the shop vac I discovered while preparing my new flagstone patio for grouting.

I'd like to try some of the less lethal controls early in the spring. Can I use the soap without killing off all the beneficial insects?

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