18 August 2015
There is something particularlyinsidious about anything or anyone which carries out its attack in a sneaky,hidden-away sort of way, and when it comes to garden pests, one that fallsfirmly into this category is the leatherjacket. At this time of year they are likely to be lurking in your garden,especially the lawn, that area that was once green and lush but which is nowlooking somewhat yellow and a bit miserable. If leatherjackets , the larvae of crane flies or daddy-long-legs havecaused your garden grief in the past then the great thing is that there areeffective controls you could use right now.
.The first symptom that isnoticeable is usually the rather yellowed, miserable patches of grass thatdevelop, often within a lawn that looks perfectly healthy. The grass is no longer firmly attached to thesoil beneath as many of the roots have been nibbled away and so if you tug atit, tufts often come away easily, or may even be pulled up by the mower bladeswhen you mow the lawn. Leatherjackets may also cause damage in other areas of thegarden, especially the vegetable plot and flower beds where they will eat theroots of various plants, especially when these plants are still young andimmature.
The leatherjackets themselves areanything up to just under 2in (5cm)long, but more commonly about 2.5cm (1in) with a soft, tubular, greyish brownbody that has no clearly defined head-end. They are found beneath the soil surface, or occasionally on the lawnsurface after a period of heavy rain.
What do they attack:?
The main source of food for thecranefly larvae or leatherjackets is plant roots. Grass is the number one favourite, but manyother ornamental and edible plants can be attacked. If you are unsure as to whether they arecausing trouble you may notice the tell-tale signs of birds (particularlystarlings) , foxes and badgers that dig up your grass, often causing extensive ripped-up patches of lawn. Because of this habit, these animals areoften wrongly accused of being responsible for the lawn grass yellowing, infact they are simply digging up the turf as they search for the leatherjacketswhich they regard as a delicious food!
If you are unsure as to whetherleatherjackets are responsible for the yellowed patches on your lawn, set a‘trap’ for them. Early one evening waterthe grass well in one of the affected areas, cover this area with blackpolythene weighed down with a few bricks. If leatherjackets are involved, when you lift off the polythene earlythe next morning you should find them beneath the polythene on the lawnsurface, often nested on the squashed grass.
In August the adults of theTipula and Nephrotoma spp of insect, (craneflies or daddy-long-legs) beginlaying their eggs i9n the soil and often around grass plants. The eggs are ready to hatch after about 14days. The young larvae, also known as leatherjackets feed on plants rootsthroughout the late autumn,
through the winter and in tospring. They feed even more voraciouslyduring the early summer and then pupate. In August the whole cycle starts again as the adults orcraneflies/daddy-long-legs start toemerge from their pupae, and are often seen in large numbers above the grass,especially early in the morning. They then start to lay eggs and the cyclebegins again.
Prevention and Control:
Dealing with underground pests such as these is difficult especially since by the time the larvae havebecome big enough to see easily they have already done an awful lot ofextensive root nibbling.
It is possible to trap large numbers of the leatherjackets using theblack polythene bag technique mentioned above, but it is essential that thesoil or turf is watered or rained on very thoroughly before the polythene islaid down. The great thing about thismethod of control is that the numerous larvae you collect make an excellentaddition to the bird table!
There are no chemical controlsthat I can recommend. There is however avery worthwhile biological control using a pathogenic nematode such asSteinernema feltiae. This can be wateredon to the soil from about the end of August until about the end of October andthe nematodes will then enter the leatherjacket’s body and release bacteriathat then stop the larvae from moving and kill them within a few days ofapplication. It is totally safe for use in gardens with pets and is also totally safe for wildlife and humans!! For this treatment to workit is essential that you follow the instructions closely, wet the soilthoroughly before and after application and keep the soil moist for about 2weeks following application. The soilalso needs to have a minimum temperature of about 14C (57F), but this should not be a problemat this time of year. Available from this website just click on the New Products Available image and when you've ordered we will send them out to you really quickly !