Tuesday, 1 October 2013

Integrated control of slugs with Cobra

Controlling slugs needs more forethought as growers now need to adhere to the strict Stewardship guidelines for the application of metaldehyde-based slug pellets in order to avoid risk of water contamination. With significant dose rate restrictions for this type of product being advised as part of this Stewardship - just 210 gms as/ha between the 1st August and the 1st December - integrating alternative active ingredients, such as methiocarb, into the slug control programme is the obvious way forward.

Stewart Woodhead, newly appointed Technical Manager for Interfarm, points out that cultural methods of control and in particular creating firm fine seedbeds will be the first option to limit slug activity.  “Cloddy seedbeds attract slugs. Shallow cultivations will incorporate last years’ stubble which once again attracts slugs. Then growers can look at using slug pellets when there is a confirmed need. It makes sense to use a proven high quality product with a different mode of action which helps avoid the water contamination problem in the first place.”

He points out that the low dose rates of metaldehyde form a key part of the Stewardship guidelines and must be adhered to if water contamination is to be avoided.  “As the Metaldehyde Stewardship Group quote on their Get Pelletwise web site (http://www.getpelletwise.co.uk )  “Know when to stop - once metaldehyde maximum limits are reached (max is 210g/ha in the autumn or 160 g/ha or less where suppliers/ BASIS advisors recommend reduced rates) do not use metaldehyde. Switch to an alternative method of slug control.”

Stewart suggests that growers should consider introducing Cobra as this alternative. “Containing 4% methiocarb, Cobra is a modern high quality wet extruded pellet, which maintains its integrity, even in wet conditions. It is very durable and gives long lasting persistence. It also has good ballistic properties for an even application on the soil surface. Methiocarb is more than eight times less soluble than metaldehyde. This means lower risk of contaminating surface water. Although Cobra has no LERAP, it must be kept out of watercourses.

He also explains that methiocarb works in a different way to metaldehyde.  “Methiocarb is a stomach poison and so slugs which feed on Cobra pellets rarely recover, unlike metaldehyde which works by making slugs produce mucous leading to dehydration. Cobra also continues to work effectively, when it is cold and wet. It is still effective down to 2ÂșC. It makes sense to integrate another pellet with a known different mode of action within the programme.”

Stewart advises growers to monitor winter cereals for slugs from sowing to the start of tillering and to monitor oilseed rape from sowing to four true leaves.  “When traps indicate the threshold has been exceeded and if the weather is conducive for application, then pellets can be applied. Oilseed rape is particularly susceptible as slugs are able to damage the growing point of the plant which, unlike cereals, is above ground.”

Cobra is recommended in winter wheat, winter barley and oilseed rape at a maximum dose rate of 3.75 kg/ha, with 2 applications per crop (up to 7.5 kg/ha). It has full label recommendations for a range of other vegetable and horticultural crops including potatoes.

Marketed by Interfarm UK Ltd, Cobra is a wet extruded pelleted bait containing 4% w/w methiocarb and packed in boxes of 2 by 10 kg polybags. It is used for the control of slugs, snails and strawberry seed beetle and for the reduction in leatherjacket populations. It is recommended in barley, Brussels sprouts, cabbage, cauliflower, forage maize, oats, oilseed rape, outdoor lettuce, outdoor spinach, potatoes, rye, strawberry, sunflower, triticale, wheat and all non-edible crops.