Here in Canada, we’ve been talking for years about research on the highly effective method of dipping your poinsettia cuttings in low-risk pesticides to reduce starting whitefly populations.
Thanks to Dr. Rose Buitenhuis (VRIC), Cary Gates (FCO) and BioWorks, the label for BotaniGard WP has now officially been expanded to include dip applications. This now adds to our arsenal (see below for more dip products).
Read on for the current BotaniGard label and how dipping can help improve your Bemisia whitefly program this year, whether you’re using pesticides or biocontrol.
WHEN to Dip:
This week and next are when many growers are still receiving their poinsettia cuttings, so NOW’S THE TIME to add dipping to your whitefly control program.
For best results, cuttings should be dipped soon after receipt. Once dipped, allow cuttings to dry before sticking and placing on the misting bench.
(In bad whitefly years, I’ve also heard anecdotal reports of growers successfully dipping after rooting, while the cuttings are still in trays. Trays should be turned upside-down in the dip tank; contact of the dip solution with the root area should be avoided).
WHAT to Dip:
Recent CANADIAN label registrations include BotaniGard WP (see the most current label by clicking the registration number for BotaniGard WP here) and Kopa insecticidal soap (here), both for whitefly nymphs. Together, BotaniGard and soap are the most effective treatments for whitefly (see Figs. 2 and 3 below).
Suffoil X was also recently registered for whitefly on greenhouse ornamental cuttings in general (see label here) and can be highly effective (see Fig. 3 below). However, rates given on the label are MUCH HIGHER than have been reported by VRIC researchers to be SAFE for most plant cuttings. To avoid phytotoxicity to poinsettia, reduce rates to 0.1% Suffoil (1ml/L water). Rates higher than this can cause burn when used as a dip, and simply aren’t necessary.
Additionally, both Suffoil X and Landscape oil (see label here) are registered as dips for THRIPS control. (Check back for an upcoming post to help you plan your spring crop season!). Again, rates for Suffoil should be lowered to under 0.1% to avoid phytotoxicity. Always test a small batch of cuttings first, and reduce again if necessary.
For our readers in the United States, BotaniGard WP is also registered for dips, as are Rootshield and Rootshield plus, which some growers add to their dip solution to help control disease in poinsettia, such as Pythium.
Overall, dipping provides MANY benefits, including:
- Dipping cuttings in insecticidal soap (e.g. Kopa) and BotaniGard WP can reduce final whitefly populations by 70% (see more here) if used in combination with biocontrol (see Fig. 2). If you don’t want to use soap, BotaniGard by itself reduces whitefly nymph survival by ~40-50% compared to a control (water) or a soap-only treatment (see Fig. 3, below).
- Even when using a chemical control program, by reducing the initial whitefly pressure, dips can decrease the amount of pesticides needed on poinsettias by 50%, according to Dr. Rose Buitenhuis.
- Given the reduce-risk products used, dips are 100% compatible with whitefly biocontrol programs.
- Dips may also benefit whitefly biocontrol by helping to rinse off pesticide residues, allowing for better survival of natural enemies like Delphastus.
- Dips pose little risk in spreading the poinsettia pathogen Erwinia, though other pathogens (e.g. Pythium) have not been tested.
More information on the Vineland Research and Innovation Centre’s research on dips can be found here and here, and a video demonstrating proper dipping techniques can be seen here. Dips are fairly simple, but taking care to make sure ALL the cuttings are immersed in the solution is key.
To make sure your dipping program is successful, below are a few tips for dips:
- Dip rates are lower than spray rates for soap and oil to prevent phytotoxicity. But always test a small batch of cuttings before committing to a full dip program.
- Place unrooted cuttings in a mesh immersion tray with a lid for dipping. Total coverage of the foliage is required for dips to be effective. Do not pack the cuttings too tightly.
- Verify that there are no dry surface areas after dipping to make sure your technique is effective.
- Good sanitation is essential. Research has shown that the risk of disease transfer through the dip solution is low, but pathogens may still build up. Don’t re-use dipping water. Ideally, dip water should be changed every 4 hrs.
- Don’t use on weak or stressed cuttings, and don’t expose the dipped cuttings to full sun.
Now that product registrations are approved for dips, this preventative technique will likely form the backbone of many greenhouse pest control programs, whether they be pesticide OR biocontrol based. Happy dipping!