Root weevils are beetles with snouts. They may look funny but they’re a serious problem for the acid-loving plants like rhododendrons. Like beetles, they are of the order coleoptera.
You’ll know you have weevils when your see the characteristic “notch” – a ¾ diameter circle – bitten out of the side of the leaves.
But it’s what they do below ground that should really scare you. From the earliest larval stage, they feed voraciously on plant roots and will go after the main stem just beneath the level of the soil. As adults, they roam the entire plant, chewing up root systems, stems and leaves without mercy.
However, weevils can’t fly. They have to take up daily residence in the soil and that’s the best way to combat them.
They’re nocturnal. So you can defeat them with any form of trap that takes advantage of the fact that, everyday, they’re running towards the darkness.
Spreading Tanglefoot on a band girdling the main stem allows you to pick them off when they travel up into the foliage at night and back into the ground. Laying boards - or even sheets of dampened newspaper - around or near your shrubs provides a hiding place from which you can remove them at frequent intervals.
As soil dwellers, they are particularly vulnerable to nematodes. A nematode mixture poured into the soil and kept moist will help you combat weevils each stage – from eggs, through larvae and pupa to adult.
Another suggestion is to plant garlic around your shrubs. They don’t like the smell.
And always try keep branches and leaves from touching the ground – it just gives them another easy path up into the plant.
The root weevil is usually 8 to 18 mm long, brown to dark gray in colour. It has 6 legs and two antennae. But you’ll always recognize it by that little, blunt snout.