Are Leatherjackets a common problem in the UBC/West Point Grey area? The nematode treatment is very expensive. Sould it be considered as a preventive treatment or is it best to simply monitor in Autumn?
I suspect that the Leatherjackets at West Point Grey are no different than the ones in Burnaby: they come in cycles. They are numerous some years and scarce in others. Judging by the numbers of Crane Flies that I've seen, this is nowhere near a peak year. I certainly wouldn't waste effort or money by treating a lawn in an off year. If the damage is severe, treatment may be warranted, but I've never even noticed any damage from Leatherjackets even when Crane Flies are abundant. I suppose some of the racoon holes in the lawn may be from their digging out Leatherjackets, but I view that as free lawn aeration.
I'll add some general information to this. In the Vancouver B.C. area, we now have two species of Crane Flies. You may recall a huge Autumn infestation in the early nineteen seventies. Since then we have also acquired a spring time Crane Fly species that got here from Europe. The Crane Fly itself doesn't do the damage. It's the larvae that are eating the grass roots that can be a problem. The Larvae turn into the Crane flies and by then, any damage to your lawn by the Larvae is done. The Crane flies are the end of the life cycle. There is no need to be afraid of them, nor do they actually cause any damage. If you have brown spots and dead areas, then dig up some of the turf and count how many Larvae you have per square foot. Your grass can easily handle twenty five to fifty of them per square foot before there is serious damage. Keep in mind too that the European Chafer grubs look similar to the Crane Fly Larvae. The last two years have been slow for the European Chafer. I advocate the use of the nematodes, but if you are allowed to use pesticides and want to, you could have your licensed pesticide applicator/landscaper spray your lawn with a product called "Sevin". (Canadian name) Carbaryl is the chemical name. It can be used any time of the year for grubs of all kinds. Another pesticide that can be used in Canada for grubs like the European Chafer is "Merit" (first and second week of July only) If you're reading this in another country, please check with a professional to see what pesticides you are allowed to use there on grubs. If you don't want to use pesticides or aren't allowed to and the nematodes are too expensive, then try soaking your lawn so the grubs come to the surface. Perhaps the birds will feast on them.
Thank you for this very complete and informative reply. Digging up a sample of brownish lawn sounds like a good idea.
