It will soon be that time of year again, when Japanese beetle adults begin to fly!
However, the cooler spring means pupation may take longer. So what does that mean for timing of control products?
This post answers those questions and provides current infographics for JB control for those exporting to non-JB areas.
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.
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.
Pesticide Considerations for 2021 and Beyond
When Can Acelepryn Be Applied, REALLY?
Last year, we’ve had several growers ask us to clarify whether Acelepryn can be used as a curative treatment for shipments of ornamentals from Ontario after April 30th (which appears to be the cut-off on the infographic, above). The short answer to this is technically, YES, BUT UP TO A POINT.
Why is this? The answer is two-fold:
- WE NEED TO CONSIDER THE PRODUCT LABEL AS WELL AS RISK MANAGEMENT: the label, as the legal document for any registered product in Canada, suggests that Acelepryn is efficacious on JB when applied from early April to early September when the HIGH rate of Acelepryn is used (as indicated on the JB Control Timing chart, above). HOWEVER, it is well known that most pesticides are less effective against the pupal stages of insects than on larvae. Because the movement of JB can result in quarantine and trade issues, OMAFRA is no recommending the use of any product once the suspected pupation period of JB has begun.
- WE ALSO NEED TO CONSIDER THE WEATHER AND INSECT BIOLOGY: Being ectotherms, the development of insects is mostly dictated by how warm, or cold, the outside temperature is. Given the cold spring in 2020, OMAFRA extended the recommended curative Acelepryn application date to May 21st in 2020, since JB pupation was likely delayed (based on observations of adult flight period). Given the same cold spring in 2021 (at the writing of this post on June 11, we haven’t seen a single JB adult yet!), application of Acelepryn can also be safely extended to May 21st in 2021, if you happened to apply it late this year.
So, the bottom line is that, since pesticides tend to be less effective against the pupal stage of insects, OMAFRA’s recommendation is currently that this product should only be applied UP TO the pupation period (WHICH CAN BE CONSIDERED TO BE MAY 21, 2021), but NOT DURING.
This is to reduce the risk of spreading this invasive pest and jepordizing export relationships in the process. We have confirmation that CFIA agrees with this clarification. With proper planning using the new modules under the GCP, few instances should occur where growers are caught needing to apply products between May 15th and June 15th.
You can download the current JB Timing Chart and Decision Tree here: