I have had a report of June beetle grub damage earlier this week. From the photo, it appeared that they were early third instar. There was already damage from grub feeding at these sites and the bad news is that the third instar grubs will be feeding all through the fall so there is more damage to come. I am not aware of any nematode species that are effective against third instar June beetle grubs.
We know that European chafer grubs are developing on schedule on irrigated turf sites and they are now in the first instar. It is very difficult to predict what may have happened to European chafer eggs on sites where there has not been significant rain during their egg-laying period. Usually female adult European chafers will seek out sites with sufficient moisture to lay their eggs. That may have been a difficult task for them this summer. If they were unable to find moist sites, there is a chance that their eggs did not develop. If they did find moist sites, it could be that grub damage will be in the low lying wetter areas instead of the usual high areas with light textured soils. We will be doing some grub monitoring in the upcoming week and I will write a post on what I find. There is also the question of when to start nematode treatments this summer. There is still time. Generally speaking, conditions are still on the dry side, although there were some widespread thunder showers yesterday. Nematode treatments work best is soils are moist at the time of application and if they can be kept moist for several days after. If there are watering bans in your communities, you or your clients may need permits to water lawns after a nematode treatment has been made. Nematode treatments can easily be delayed for a couple of weeks without sacrificing efficacy. I would welcome any feedback on what people are observing regarding European chafer grubs so far this summer.
Japanese beetle adults live a lot longer than European chafers. It is possible for them to delay their egg laying until conditions are more favourable. At GTI, we have still seen large numbers of adult Japanese beetles on feeding on ornamental plants. It is predicted that the dry conditions will not impact their numbers for this fall.
The other Scarab grub species that is past its damaging phase is the black turfgrass ataenius. We are seeing some damaged short mown turf, but once we pull it back to find out the cause, all we see are black turfgrass ataenius pupae. At least with this insect there is no need to worry about more damage until next season.
I would like to know if it is a good idea to rake the dead grass before our lawn is treated with nematodes. There isn’t a lot of thatch, but I wonder if a light raking would help the nematodes get past the dead grass. Thanks.
The critical thing with nematodes is getting them to the grubs and the best way to do that is to make sure that the nematodes get watered in. Raking the dead grass will help if you plan to overseed.