Now that the growing season is in full swing, it is important to keep an eye out for anything that can cause destruction to our summer bedding and shrubs. One of the most successful soil pests at doing this is called the Vine Weevil (Otiorhynchus sulcatus). It is indeed public enemy No.1 and it is particularly rampant in containers but they may also be found in beds and borders. Once these pests have invaded your plants and their larvae invaded the roots, there is very little you can do.
ADULTS
The adult Vine Weevil is a dusty black/grey flightless beetle and they are all females. They can lay up to 1000 eggs in a season and the eggs are laid just under soil level at the base of the plants. They are about 9mm long, with a short snout and elbowed antennae. They feed at night, nibbling away at the edges of leaves and they hide under garden debris during the day. They are crafty in that if they are disturbed, they often play dead. Signs of adult Vine Weevil presence includes notches appearing on the leaf margins, often close to the ground, as they are unable to fly. They are, however, very good climbers so no window boxes, containers or hanging baskets are safe.
GRUBS
It is not the adults that do the most damage but their babies, which are white in colour with brown heads and are slightly curled into a C shape. They devour the roots and outer tissue of woody plants and they often remain undetected until it's too late, so if you notice the adults, you can be certain their larvae are there too. The grubs are not fussy what they attack. They love Rhododendrons, Camellias, Hydrangeas, Fuchsias, Impatiens, Primulas, Begonias, Sedums and Strawberries, in fact almost all plants and particularly if they are container grown.
SYMPTOMS
These little vandals simply munch away at the root systems of the plant until either they are caught or the plant first yellows, then wilts and collapses through lack of sustenance. The adults lay their eggs in the summer and autumn, so the grubs hatch the following spring ready to begin attacking any plant they can find.
TREATMENT AND CONTROL
Control of Vine Weevil is difficult although you can deter them by keeping the garden clean and tidy by removing plant debris regularly to reduce the numbers of hiding places. If you are not squeamish you could go out at night as you would with slugs and snails and collect the little nasties. For container grown plants Vaseline can be rubbed around the rim of the pots to prevent the adults from gaining access and a mulch of ornamental gravel or slate may be applied over the surface of the containers to prevent the females laying their eggs into the surface of the soil close to the stems of the plants. There is a drench available which is applied around the soil of the plants and it can control Vine Weevil for up to four months at a time. However, if you do discover a heavy infestation of Vine Weevil grubs in your containers the best action is to remove the plant from the infested compost or soil, wash the roots thoroughly, replant in fresh compost and more importantly dispose of the infested compost or soil in a bag. Do not under any circumstances must it be placed in the compost heap.
JOBS OF THE WEEK
* Continue to remove side shoots from tomatoes, tie in the main stem and feed weekly with a liquid feed high in potash.
* Weed beds and borders and cover with a mulch to prevent weeds re-emerging.
* Check for mildew on roses and honeysuckle and spray if necessary.
* Mist houseplants and feed and water regularly.
* Check for slug and snail damage on containers and herbaceous plants and use your preferred control.
* Check containers for signs of Vine Weevil attack and consider your options for control.
