Technical
“ Chafer Grubs
The real damage is done by predators such as starlings, rooks, crows, jackdaws, magpies, foxes and badgers that make the most of an abundant, high protein food lying just beneath the surface
120 I PC JUNE/JULY 2016 ”
Damage to turf can be seen from
September through the autumn, winter and into the spring. The lifecycle of both species means that they can pupate at two times of the year
Major damage to the turf can be done by
predators that are after an easy and abundant meal. Starlings, crows and other birds can congregate in vast numbers and decimate surfaces in a short period of time. Damage to turf can be seen from September through the autumn, winter and into the spring. The lifecycle of both species means that they can pupate at two times of the year. The vast majority of Crane Flies hatch in August and September, but there is also a small number that pupate in the spring (April and May). The illustration above shows the two lifecycles running concurrently: It can be seen that the most effective time to apply nematodes to control the larvae of leatherjackets is in the autumn. This is for two reasons:
- Both lifecycles coincide, enabling a single period when both lifecycles can be effectively treated
- As the larvae become older, nearer pupation, nematodes become less able to penetrate the skin and, therefore, a greater number of nematodes are required to be as effective
It can be seen that a preventative approach is required for effective control; treatments in the early spring when symptoms of leatherjackets are evident will have limited ability.
There are six species of Chafer beetles, the adult form of the chafer grub, in the UK: the Welsh Chafer, Summer Chafer, Brown Chafer, Cock Chafer, Garden Chafer and Rose Chafer. The most familiar being the Cock Chafer or ‘May bug’, a large beetle that can be heard as a low droning noise on pleasant spring evenings. They have stout white bodies curved in a C shape, light brown heads, with three pairs of legs and darker patches at the base of the abdomen. They are bigger than the adult beetles, although their size varies, according to species, between 8-35mm. They live within the soil for up to 3-4 years, going through various ‘instars’ (stages at which they moult their exoskeleton) as they develop. Again, the real damage to turf is done by
predators such as starlings, rooks, crows, jackdaws, magpies, foxes and badgers that make the most of an abundant, high protein food lying just beneath the surface. The lifecycle of a chafer grub is illustrated below and explains that the most effective time to apply nematodes will be between mid-July to mid-October, when larvae are large enough to encounter the nematode, aren’t a significant issue in turf, but before soil temperatures are lower than 12O
C and the grubs move lower down in the soil profile.
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