A deciduous azalea bush just finished flowering in the garden of a house we recently purchased. Within days after the bloom finished, we noticed that...
Knowledgebase
Azalea leaf pest #634272
Asked May 11, 2020, 7:45 PM EDT
A deciduous azalea bush just finished flowering in the garden of a house we recently purchased. Within days after the bloom finished, we noticed that the leaves are nearly entirely decimated. Attached is a picture of the small green caterpillars that seem to be eating on the edges of the leaves, leaving only the central vein. Is there any treatment that you can recommend, or is this fatal? We estimate that this shrub has been here for many years, but we recently removed most of the shrubs around it and had the stumps ground. Thank you for your assistance.
Washington CountyOregon
Expert Response
Thank you for the images.
Once your eye "learns" how to spot them, you can
easily handpick and drop into soapy water. They typically feed from the
leaf edge.
The culprits eating your azalea leaves are sawfly larvae
(youngsters). They’re difficult to see
because they are the same green color as the leaves. They resemble caterpillars
(“worms”) and, as you've noticed they're less than a half-inch long. Look for them on the, edges of the
ravaged leaves. Or on the midribs.
If you see small brown specks, it’s
sawfly frass (excrement); the sawflies should be nearby.
Azalea sawflies specialize on deciduous azaleas. And, yes, they also eat the flowers. Even so, the azalea will survive.
The sawflies tend to be sporadic. They'll damage the shrubs for several consecutive years, then no damage for a while -- I don't know for how long.
If the shrub is a
reasonable size, handpicking works. (If you’re squeamish, use tweezers or gloves) Or
flick them into a cup of soapy water. Another option is a harsh water spray to
blast them off the plant.
If you
decide to use a spray, know that both azadirachtin (neem extract) and spinosad
A&D are considered organic choices.
Thank you so much for a speedy and thorough reply! I value this service tremendously! I washed the azalea thoroughly with a hose end sprayer with one teaspoon each Dawn liquid and baking soda per gallon water. I found only one living caterpillar the next day. Do you think it will send out new leaves and survive or should I plan to remove it? If I prune it, might that stimulate some new branch and leaf formation? Thank you!
Deciduous azaleas which have all their leaves by the sawflies will grow and bloom again next year.
Fortunately, the sawflies are typically sporadic. But, when extensive leaf loss occurs every year, the shrub may be weakened and can die.
Do not prune the azalea this year. Doing so removes some of the shrub's reserves which are needed for recovery.
The azalea won't leaf out again this year. But it will survive.
A caution: Home remedies such as a combination of dish soap and baking soda can seriously injure plants. The preferred application is a commercial insecticidal soap, diluted according to label directions.
