Biological control one option in the constant cutworm conflict

Handpicking, collars and bio-insecticides are key in the war against voracious cutworm, writes Kitty Scully.

Gardening is a past time synonymous with physical and psychological well-being as well as a being a pastime, or career, even, that presents a multitude of rewards.

However, every now and again it can be confused with warfare and I personally, am waging a constant war against cutworms at the Airfield Food Gardens.

Cutworms are the caterpillars or larvae of several different species of nocturnal moths. 

There is no confusion as to how they got their name, as these soil dwelling pests simply cut down young plants as they feed on stems at, or below, the soil surface. 

Have you ever found a newly-planted lettuce suspiciously wilted and leaves looking ripped and lying on the ground?

Biological control one option in the constant cutworm conflict

Well this was most likely the handiwork of a ravenous cutworm. Being a generalist pest, they have a voracious appetite for a range of common vegetables but in my experience, salads, chicory, brassicas and Florence fennel are among their favourites.

Identifying these hungry feeders is not difficult. Generally if you disturb the soil around and under a vegetable victim, a fat larvae, dull brown-grey in colour will be lurking. 

These can grow as large as two inches long and when disturbed they curl up into a tight ‘C’.

They have the potential to produce three generations in one year with some larvae overwintering in weedy areas and grassy verges. 

This gives good reason to keep beds weeded and plots tidy after crop harvest to ensure potential host plants for overwintering larvae are removed. 

Populations of cutworm appear to be greatly influenced by the weather, with dry conditions resulting in increased cutworm activity.

Cutworms mostly feed at night and can be found outdoors and within tunnels at almost any time of year. 

Biological control one option in the constant cutworm conflict

That said they seem to be at their worst in early spring and at this time of year. Last year in Airfield we lost approximately 30% of our newly transplanted overwintering salads in cutworm combat.

This year, forewarned is forearmed and as with all garden pests, observation, identification and early detection is top of the arsenal for cutworm control.

As cutworms like to munch through stems of plants at ground level, disturbing soil around seedlings to expose the culprits and subsequently hand picking is effective. As one cutworm has the potenial to damage lots of plants, hunting individuals is worth the effort.

Keeping ground weed free to remove egg laying sites is vital. Regular cultivation of soil will also reduce populations as cutworms will be exposed and can be removed while digging. 

Keeping soil moist at all times can help keep numbers down while some experts recommend that susceptible plants be protected with a collar made from cardboard or aluminium foil.

If placed properly, ie pushed a few inches into the soil, these collars are thought to create a physical barrier to prevent these ravenous larvae from feeding on tender plants.Handpicking and collars are labour intensive if one is dealing with a large area, and in this incidence, biological control may be the only weapon worth employing.

Biological control one option in the constant cutworm conflict

After all, every living thing is subject to predation, parasatism or competition from other creatures. One bio-insecticide I have used in the combat with cutworms is Supernemos. 

Now bio-insecticides and biological control sound very scientific and technical, but you will be glad to know that no specialist equipment or knowledge is needed to use this useful cutworm controller. A bucket, watering can, water and an old measuring jug will suffice.

Supernemos basically are a uniqe mixture of natural beneficial nematodes formulated to attack several grops of insect pest. 

These microscopic nematodes, once applied properly, kill target pests within a few days of finding them with no ill effect on beneficial soil dwelling insects or the environment. 

Other pests that Supernemos attack include leatherjackets, vine weevils and wire worms. Note that these nematodes do not feed on molluscs or slugs.

Supernemos work best in controlled areas and henceforth are well worth the investment for a polytunnel destined to be filled with winter salads early next month, or for those who garden mostly in pots and containers.

Heavy infestations can be treated with a single application at full strength but like with most pests, successive generations can be a real problem, so two applications at half-strength is recommended.

Supernemos are fully certified for use on organic holdings and are easily availalbe to buy in Ireland. Some good garden centres stock the product or it can also be ordered directly online at:  or alternatively, phone: +353 (86)8256302


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