Monday, March 18, 2019

What are these notches on rhododendron leaves?

notches on rhody leaves
Many landscape plants will show leaf notching as new leaves start to grow in spring and early summer. Rhododendron is particularly susceptible but a number of other popular landscape and garden plants may show the same type of damage. Often you will not find any obvious cause or culprit.

The cause and culprit in this case are adult root weevils (snout beetles). There are many species of root weevil (Curculionidae) but all exhibit the same general life cycle. Worm-like larvae feed on plant roots for most of the year, adult beetles (weevils) emerge from the soil in spring or summer, feed (notch) on leaves of the host plant, lay eggs then die. The real damage therefore is to the root system of affected plants but it is the leaf notching that catches the attention of gardeners.

black vine weevil adult
The best way to protect your landscape and garden plants from root weevil damage is to control adult weevils in the spring and early summer before they have a chance to lay eggs for the next generation of root-feeding larvae. So, timing is critical.

Fortunately leaf notches are a perfect way to time when adult weevils are starting to emerge and feed. As soon as you see new notches appear in spring/early summer start your control program!

Leaves can be treated with a variety of garden insecticides to stop weevils from feeding. Neem oil insecticide is a low toxicity choice that works well.


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