Vine weevil – are you prepared?

Historically one of the most serious pests in ornamental plant production, Black Vine Weevil feed on a wide variety of ornamental plants.  The root-feeding larval stage is the most destructive, greatly reducing growth and, if left uncontrolled, can eventually kill the plant. To achieve adequate control necessitates forward planning, as well as an understanding of the pests’ life cycle and available control products. With pest larvae due to pupate over the coming months, Sam Rivers, ICL Technical Manager for Controls, provides a timely overview.

What is the lifecycle of Vine Weevil?

In an outdoor situation, adults typically emerge in April-May, but this can be earlier depending on factors such as temperature. Once the adults emerge, irregular notches along leaf margins of susceptible plants are a useful early indicator of an infestation – as the nocturnal adults generally remain hidden during the day.

After a couple of weeks feeding on the foliage, the adults head down to the ground to lay their eggs.  A single adult can lay up to 830 eggs with viability of around 80%, so within a year a small problem can become a major issue.   As autumn approaches, the adults start to die out while the newly hatched larvae seek out plants’ roots to overwinter. Having fed on the roots throughout the colder months, they pupate in spring, and the annual lifecycle starts again.

What are the control options for Vine Weevil?

Over the past 40 years, several effective chemical control options have come and gone. However, UK growers do have targeted biological options available from which to formulate effective IPM control programmes.  LALGUARD M52 GR and beneficial vine weevil Seeka nematodes are tailored to different stages of the pest’s lifecycle and environmental conditions.

So, where to start? Cultural control is the first line of defence in any IPM plan.  In respect to vine weevil, keeping the nursery site free of weed and debris is key – places where adults can seek refuge. Introducing a regular monitoring programme – especially focusing on the most susceptible stock – can help inform management decisions as well as the next steps in terms of the control products to use.

Top tip:  If buying in susceptible stock, it is good practice to quarantine it until you can be certain it’s free from vine weevil – and any other pest/disease for that matter.

Growing media incorporated Lalguard M52 GR

The bioinsecticide LALGUARD M52 GR is based on the spores of soil-inhabiting insect pathogenic fungus Metarhizium brunneum strain Ma43.  Unlike bacteria or viruses, it does not need to be ingested to be effective and infects on contact.  Easy to use, this granular formulation can be growing media incorporated saving valuable application time.

At 15-30°C, infected immature black vine weevil larvae can be killed within three days.  Meanwhile, the egg and pupal stages also show some susceptibility – adding to the overall effectiveness of control.

Highly compatibility with existing plant protection products, such as beneficial nematodes, Lalguard M52 GR is an important component of robust vine weevil IPM plans.

Hot off the press: Lalguard M52 GR has been awarded organic certification! Click here for more information.

Target nematodes carefully

Beneficial nematodes target the larval stages. When applying, substrate temperature is an important consideration. For pot temperatures above 12°C we recommend Vine Weevil ‘Seeka’, based on the beneficial nematode Heterorhabditis bacteriophora. Below 12°C we recommend switching to Vine Weevil ‘Seeka CT’ (cold tolerant), based on Steinernema kraussei – a species that works well from 5-30°C.

Top tip: To monitor effectiveness, before applying nematodes flag plants with vine weevil larvae present.

Plant Health Planner – here to help

To help growers plan, simplify and optimise their plant health programmes on their nurseries year-round, we have developed a new digital web-based tool – the ICL Plant Health Planner. In line with the Sustainable Use Directive, our Plant Health Planner is helping growers reduce their reliance on chemical crop protection products.

For find out how the ICL Plant Health Planner can help you, or for more information on any of our vine weevil control products, speak to your local Technical Area Sales Manager.