Vine weevil are possibly the biggest garden pest in the UK. I use the term biggest in so far as nearly every garden, nursery, garden centre and indeed container either has them or has visible signs thet they have been present. The weevil live mainly in amongst dead leaves , under larger leaves on plants or down the side of containers between the compost and the container itself. They are capable of laying up to 1000 eggs each. The eggs are laid in the soil where a good source of food is not too far away. The larvae hatch and feed on the roots of plants. The larvae is a creamy white colour with a brown , orange head. They vary in size depending on age. If you come across a plump white grub that looks as though it has just enjoyed eating your plant roots ot is probably a weevil larvae. Another sign to look for is the soil or compost in the pot often takes on a very fine orange or brown powder effect. Generally compost in a pot will be firm and held together with small plant roots. Once weevil larvae are present the compost will fall away from roots and appear soft. The larvae changes in to a pupae stage before becomming an adult weevil. The adult is a dark brown colour with a rough , serrated shell. The shell is hard and compared to common garden beetles it is not shiny.They are generally slow moving during the day where a more common , garden friendly beetle will scurry away frantically.
The adult is normally only active at night. Damage caused is notches out of the leaf edges. They like fleshy plants along with evergreens. Nothing is safe however. Slug damage varies fron notches out of leaves to holes in the centres. Weevil only damage the edge. If plants in the garden are damaged it is unlikely you will see any adults in daylight. You can shine a torch along the stems and under leaves at night and remove any adults found. If the plants damaged are in pots , empty the pot and check all around the compost. They may have buried themselves into a small hole so check thoroughly.
We use a number of methods to control weevil. We have free range poultry which rake around outside the nursery and hopefully eat any grubs and weevil they come across. We introduced a pond inside the nursery which now has frogs, toads and newts. There are also a selection of each inside the tunnels. They found their own way ! The frogs etc eat at night when weevil are on the move and we have found proof in the past that they do eat weevil. We introduce nematodes to our pots in late summer. This is a biological control which in introduced with water. The microscopic creatures feed on weevil larvae and will kill off any they find pretty quick.Our pots are also checked thoroughly on a regular basis for any signs of adults or larvae. We also leave plant traps around the nursery. Normally some Sedum plants do the trick. They will attract adult weevil to lay their eggs. We then dispose of the plants , pots etc in autumn. Lastly we found that a pot with larvae submersed in water for 2 weeks killed off all larvae without any damage to the plant. At the moment we do not use any chemical control.
From the thousand or so eggs only a few reach adult stage.The eggs are food to other , friendly garden creatures. The larvae are often picked off by birds or eaten buy other insects in the soil. The pupae are so soft that they virtually burst when touched. The adult is the biggest problem and won't think twice about crawling through an open window at night and spending the winter inside your house. It is better to be vigilant and as soon as any signs of these pests are found take appropriate action sooner rather than later.