What are vine weevils?
Vine weevils (Otiorhyncus sulcatus) are brownish-black bugs, round 1cm lengthy, with jointed antennae and pale-brown flecks on their backs. Like aphids, the females don’t want males to breed, so it solely takes one weevil to start out an infestation. The larvae are plump, creamy-white and maggot-like, as much as 9mm lengthy. They’re normally seen curled in a C-shape, with brown heads and no legs. There are different related weevils that do a lot the identical type of harm.
Clay-coloured weevils (O. singularis) eat leaves, and their maggots gnaw the roots and bark of woody crops. They’re onerous to tell apart from vine weevils, however this doesn’t matter a lot as they’re handled in the identical method.
What harm do vine weevils do?
Grownup weevils feed on leaves, chewing irregular notches within the margins. Their mouthparts are incapable of constructing holes in the midst of the leaves. (This type of harm is prone to be brought on by caterpillars or slugs.) Vine weevils are particularly keen on camellias, euonymus and rhododendrons, although they can even feed on different shrubs and difficult herbaceous crops like bergenias.
The grubs feed on the roots of a variety of crops, each indoors and out. Nevertheless, their explicit favourites embody the next: begonias, bergenias, cyclamen, fuchsias, heuchera, polyanthus, primulas, sedums, succulents and saxifrages. They’re additionally a fan of strawberries.
Are the vine-weevil grubs extra damaging than the adults?
Sure. The primary you’ll in all probability know of an assault is when a plant wilts for no obvious purpose and doesn’t reply to watering. Nearer inspection will present that the plant has develop into fully severed from its roots. Crops are simply pulled up and are available away with out their roots hooked up.
Crops in containers are particularly liable to assault, although gardens can even develop into infested. The harm brought on by the adults is ugly however not critical.
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Are you able to clarify the life cycle of vine weevils in additional element?
The adults are lively between the tip of June and October. In daylight you would possibly spot the odd one strolling throughout the patio or on the wall of the home. If you happen to exit at evening with a torch there’s an excellent likelihood you will notice them feeding on the foliage.
The feminine weevils lay their eggs within the compost or soil amongst host crops. As a rule, this occurs in August and September, although rather a lot relies on the climate through the earlier winter and spring. In a gentle yr, egg-laying might begin in early summer season. Every feminine is able to laying 1000 or extra eggs. These eggs are lower than 1mm throughout, white at first, later turning brown. They’re troublesome to see and far smaller than the granules of controlled-release fertiliser present in container-grown crops, which are sometimes mistaken for insect eggs.
Vine-weevil grubs normally hatch after two weeks and instantly begin to feed on the roots of their host. Totally-grown grubs burrow deeper into the soil to pupate, normally in late spring. Most adults don’t emerge till the next June or July, when the entire cycle begins over once more.
Is the vine-weevil life cycle totally different indoors?
In a heated greenhouse, vine weevils can feed and breed all year long, so all levels of the life cycle will be discovered.
What can I do to guard my crops from vine weevils?
There are a number of choices. Essentially the most direct is to maintain an eye fixed open for the adults and destroy any that you just discover. Because the grownup weevils are likely to feed through the evening, it is value going out with a torch.
If just a few pots are affected, strive sifting the grubs out by hand. Squash any you discover earlier than repotting the crops in contemporary compost and placing the remaining within the bin.
What about limitations for vine weevil?
Vine weevils can not fly so limitations are helpful. Match parcel tape smeared with non-drying insect barrier glue round tubs or pots through the egg-laying season (August and September outside, or all yr in a greenhouse) to lure the grownup females earlier than they lay their eggs. For the glue to be efficient it’s essential to hold it freed from particles. Something caught to the glue, similar to a leaf or grime, will act as a bridge. Insect barrier glue is on the market from some backyard centres or on-line from suppliers, similar to Gardening Naturally and Agralan .
Are there chemical controls for vine weevil?
Sure, when Which? Gardening trialled controls we had most success with Scotts Bug Clear Extremely Vine Weevil Killer. It might probably solely be used on pot-grown crops and cannot be used on edible crops.
What about organic controls for vine weevil?
There may be an efficient organic management that’s made up of tens of millions of nematodes (microscopic worms). They kill the vine weevil grubs by penetrating their our bodies and releasing deadly micro organism. They’re equipped in a concentrated kind and must be blended with water to be activated. The soil or compost additionally must be stored moist for a fortnight after making use of the nematodes. You can even purchase traps for grownup vine weevils which comprise nematodes.
Are there any restrictions on utilizing the nematodes for vine weevil?
Nematodes are greatest used right away, however they are often saved within the fridge and used inside 12 days. The primary draw back with utilizing nematodes to regulate vine-weevil larvae outside, or in an unheated greenhouse, is that they’re very delicate to temperature. This management works greatest if the soil stays above 12°C for at the least 14 days after use. This makes August and September the simplest utility interval, although you may apply in April or Might earlier than the grownup weevils emerge from their pupae whether it is heat sufficient. By October it’s typically too chilly to cope with them outside.
Suppliers of organic controls for vine weevil