Organic farming and growing is a holistic, systems approach that aims to prevent problems from developing rather than relying on cures. Since there are effectively no quick fixes, planning and preparation is absolutely critical to achieving success. Rotation design, maintenance and enhancement of biodiversity, attention to detail, resistant varieties, and soil health should form the backbone of pest and disease control and nutrient management on the farm. These integrated measures will not eradicate pests and diseases but will serve to maintain them below economically damaging levels. Healthy soil leads to healthy plants; therefore the importance of good soil management should never be underestimated.
A limited number of restricted chemical controls are available if and when problems do occur, but these must be seen as a last resort and cannot be relied upon. These restricted products must not be regarded as substitutes for non-organic chemical inputs. Continual problems or failure of one particular crop would suggest there is an inherent problem in the system – it would be better to change this rather than fight an on-going problem. A similar approach should be considered when dealing with pests, diseases, and biodiversity – organic farmers and growers should work with nature rather than fighting against it.
Growers must consider many factors, including:
- Soil fertility and structure
- Good composting
- Crop spacing
- Field size and margins in relation to natural enemy presence
- Variety selection
- Compatibility of previous crops in the rotation
- Compatibility of the site to the crop
- Seed and transplant health
- Patience and confidence to allow a biological balance between pest and predator to develop.
If a natural balance can be achieved problems should not get out of control.
The following information is designed to increase knowledge about the problem and to give growers a number of options to work out a suitable control strategy.
Leatherjackets are the larvae of crane flies or daddy long legs (Tipula spp). They can cause considerable damage to roots and stems of many arable and some horticultural crops, particularly young plants. Problems are generally worse on land that has just come out of a ley. Damage is worst in spring, but larvae can feed right through from autumn and often occur in patches coinciding with wet areas of fields.
Life cycle
Adult crane-flies emerge from pupae in August and September. Females then lay eggs in the soil near plants. These hatch 10 - 14 days later and the larvae feed during the autumn and through the following spring (but are less active in winter), they are legless, grey-brown, fleshy grubs up to 50mm long, with tough wrinkled skins and a number of small, pointed protuberances at the tail end. High populations can develop after a prolonged warm and wet spell of weather in summer/early autumn, so consider this for the following spring when the larvae are active and are a potential threat to the crop.
Prevention
- Healthy soil for healthy plant growth to maximise the crop's tolerance to pest attack
- Use good, sturdy transplants with good root systems
- Encourage biodiversity, particularly birds. Rooks and starlings are known to have a liking for leatherjackets! Chickens will also eat leatherjackets
- Don’t grow susceptible crops on land that has been down to grass for over 2 years
- Cultivate regularly before planting to expose pests to predators
- Grow a thick green manure over the summer and turn it in before egg laying occurs in late July (mustard is reported to be good – but needs careful positioning in the rotation as it is a brassica)
- Larvae are very susceptible to drought in late summer
- Monitor levels of leatherjackets in the soil before planting. ADAS monitors populations in most regions and forecasts are issued or are available on request
- Care should be taken when planting if high levels are present in the soil – Spring cereals can be particularly susceptible if following a ley. Potatoes, leeks and lettuces are vulnerable if following a ley and sugar beet to a lesser extent.
- Keep pasture tightly grazed or cut from July to September before ploughing to reduce the chances of adults laying eggs
- Often colonies don’t manifest so major losses are not realised. Allowing a natural balance to occur is important.
- A biologically active soil will help with recycling material, particularly under a ley where thatch can build up, which gives ideal breeding conditions for crane flies.
Control
- If planting winter cereals plough grassland before September
- Timing is critical – monitor to see when highest levels occur
- Cultivations (including hoeing during crop growth)
- For small-scale use on grassed areas, can use sacking, tarpaulins or cardboard laid on the ground overnight, then collect up and dispose of leatherjackets in the morning. On cultivated land, grass clippings may have the same effect.
- Nemasys H, vine weevil biological control can be effective with leatherjackets
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Download Leatherjacket Control in Organic Systems.pdf
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