Japanese Beetles Have Started To Emerge

Japanese Beetle (Popillia japonica) adults are starting to take flight in southern Ontario! They have been spotted in Hamilton and Toronto this week.

Look for these shiny green and copper beetles feeding on grape leaves, roses and many other trees and shrubs. Where possible, homeowners can knock adults into a bucket of soapy water (to smother them). Several insecticides are registered for the adults in the nursery, including BeetleGONE and Imidan.

European chafer (Amphimallon majale) adults are also starting to emerge. Look for medium brown scarab beetle swarming blooming Linden trees (e.g. Tilia cordata). Historically we see them around Canada day in the Guelph area.

RoseChaferAdultJLA And don’t forget about our little friends, the Rose Chafers (Macrodactylus subspinosus). They are also out in full force. These scarab beetles feed on the flowers, fruit and foliage of several ornamentals. The larval stage feeds on roots of grasses and weeds (usually a sod nursery pest). Like most scarab beetles, females are more likely to lay their eggs in sandy soils and will avoid egg laying in clay soils. Insecticides for the grub stage of other scarab beetles will also reduce larvae of rose chafer.

Have white grubs (e.g. European chafer, June beetle) OR Japanese Beetle phytosanitary restrictions been an issue at your Nursery?

Preventative applications of Intercept and Acelepryn are registered for white grubs in nursery and greenhouse production and the application period begins now. (Above photo: European chafer larval feeding damage)

The following section answers those questions and provides current infographics for JB control for those exporting to non-JB areas. It is from ONFloriculture.com from Sarah Jandricic, OMAFRA Greenhouse IPM Specialist:

JB Spray Decision Tree 2020

Japanese beetle pesticide application decision tree. Infographic developed by S. Jandricic in collaboration with the CFIA. Only applicable to Ontario crops.

Step 1: Do You Need to Treat For JB at All?

As always, you want to start with this decision tree (pictured, above) to decide whether you even need to spray at all. If your plants have been grown indoors during critical periods, or you’re not shipping to areas that restrict Japanese beetle, than you might not have to.

Step 2: Pesticide Choice and Timing

Now that you’ve figure that you DO need to use chemical controls for JB, the next question is WHAT do I apply and WHEN? As there are only 3 products registered for JB control under the Greenhouse Certification Program in Ontario, the “what” part is easy (see the infographic, below).

The “when” part is a little harder, and heavily depends on timing of the JB life cycle in Ontario, and when you need to get your crop out the door.

You can either choose to treat your plants preventively (before first instar larvae show up), or curatively (when grubs of any stage are likely already present in your soil). Either way, you’ll need to understand the timing of your chosen strategy under the CFIA guidelines, and plan accordingly. Otherwise, you may end up need to re-apply chemicals, or worse – get in a situation where shipping needs to be delayed until you can put the right product on.

*JB pupa are generally less suscepetibe to pesticide than other pest stages. This affects insecticide choice and timing.*

Different products are recommended at different times of year because of a variety of factors that affect their efficacy. OMAFRA and the CFIA take these factors into consideration as much as possible when making their recommendations. A summary of our current recommended timing for products can be seen in the infographic below, and is based on these factors:

AVOIDING NON-SUSCEPTIBLE STAGES: Generally speaking, pesticides are less effective against immobile insect stages. This is either because they aren’t ingesting any of the active ingredient or because they don’t have the right receptors. For JB, our registered, soil-applied pesticides are going to have much less effect against the pupal and egg stages. Thus, for the “usual” JB pupation window between May 15 and June 15 in Ontario, pesticides are likely to be less effective, so application during this time should be avoided with careful planning. But SEE OUR 2021 CONSIDERATIONS, BELOW!
TARGETING OPTIMAL STAGES: Some pesticides are only effective on smaller larvae of JB, meaning they have a much smaller application window. Imidacloprid (Intercept), specifically, will not control the older, bigger larval stages of JB, so it must be applied when 1st instar larvae are present.
RESIDUAL TIMES OF PRODUCTS: Because chlorpyrifos (Lorsban or Dursban) only persists in the soil or media for a relatively short time, it can only be applied curatively, close to shipping, to kill any larvae that might be present.Alternatively, chlorantraniliprole (Acelepryn) or imidacloprid (Intercept) have long residual times (up to 16 weeks), meaning that they can be applied preventively once JB adults start flying, offering protection against any young JB larvae that hatch out in the soil. This is why Acelepryn can be applied during the adult JB flight period, for example.