Lacebug Infestation on Rhododendron

Asked February 17, 2020, 3:17 PM EST

Based on damage fairly certain our Rhododendrons have heavy widespread lacebug infestation. Any homesafe DIY treatments? Just learned Neem Oil now banned in Oregon. Would prefer something I can buy in concentrate form, mix and apply with my backpack sprayer - these are 12' wide and 9 foot tall mature shrubs... John

Multnomah County Oregon

3 Responses

I haven't heard any news of banning neem other than as connected with the marijuana industry. You can contact the National Pesticide Information Center (NPIC) to obtain complete and accurate information for home gardeners at 1-800-858-7378. (I normally would investigate your inquiry fully before sending a response but that would delay my response for 2 more days. Their offices are closed for the day, plus I must attend an all-day meeting tomorrow.)

Azalea lace bugs are inactive right now but they are likely to hatch in late April or early May. Right now (February), the eggs are safe and secure inside the leaves on the underside. When the nymphs (youngsters) hatch, they are easy to spot because, even though they are small, they are black and relatively immobile. As such, they are easy targets for a harsh water spray or, the usually more effective, insecticidal soap, diluted according to label directions. Repeat as needed.

Acetate, the active ingredient found in several systemic pesticides available to home gardeners, is considered a stronger pesticide than insecticidal soap.

In general, we suggest you avoid products with the active ingredient imidacloprid because this particular neonicotinoid is recycled within woody plants for several successive years. Thus, such products pose a long-term hazard for bees.

That's in contrast to the active ingredient dinotefuran, another chemical in the neonicotinoid class which is active only during the year of application.

Bottom lines:
1. You have choices, beginning with a harsh water spray and escalating to more toxic products.
2. With all pesticides, read and follow label directions for application methods and personal safety equipment.

due to product contamination many neem oil hort products are now banned in Oregon. Neither Lowes nor Home Depot will ship you these products and none are on shelves - but you can buy off the shelf in Washington
... see advisories:

thanks for your response

Thank you for the link to the update. I see the issues are to specific lots of neem-containing products due to contamination of the product with active ingredients other than neem.

As I mentioned, I won't have an opportunity to talk to NPIC for 2 days.

In any event, it's too early to apply any pesticides against azalea lace bug at this date. In order for the pesticide to be effective, must apply it until right after the eggs hatch. As previously mentioned, you have options other than neem.

Because your rhododendrons are very large, it's likely worth considering hiring a professional pest control company which has the appropriate equipment to apply a targeted spray without overspray.