Sweetpotato whiteflies Bemisa tabaci have been observed on poinsettias since early in the growing season. While many growers are using biological controls and are keeping them in check there may be situations where late season treatments may be necessary.
Some growers have found removing heavily infested lower leaves helped reduce infestations and helped improve coverage when sprays were applied. Old lower leaves that curl under can harbor large infestations of whiteflies. As bracts turn color, poinsettias become more sensitive to spray injury. In past years some growers have successfully used the following foliar sprays for late season control:
- Rycar (pyrifluquinazon) - Contact and translaminar activity. Insects stop feeding within 2 hours and adults are controlled for up to 3 weeks. SePRO reports in their technical literature that it is gentle on BCAs and pollinators. Some growers have reported success using Rycar in hot spots when using biological control for whitefly on poinsettias.
- Judo (spiromesifen) (MOA 23) – Labeled as a foliar spray and has translaminar activity. It is effective against all stages of whiteflies and has provided control of Bemisia Q and B biotypes. The Judo technical bulletin reports that Judo is gentle on biologicals particularly parasitic wasps. We are not aware of any reports of injury to bracts from applications of Judo.
- Safari (dinotefuran) (MOA 4A) – Labeled as a soil drench or foliar spray. Safari has been effective for end-of season treatment against either biotype. Expect 4- 6 weeks residual with drench applications. According to IR-4 data, it has been among the best performing products. Safari is highly water soluble and taken up into the foliage as plants grow. Drenches will not be effective on plants with unhealthy roots.
- Sanmite (pyridaben) (MOA 21A) – Contact pesticide for adults.
- TriStar (acetamiprid)(MOA 4A) – Translaminar activity for nymphs and adults.
Mainspring (cyantraniliprole) (MOA 28) is labeled for foliar and systemic use, but is best used early in production. The Syngenta bulletin “Mainspring Best Practices Q&A” recommends application no later than the second week of October. It is also compatible with Eretmocerus.
Kontos (spirotetramat) (MOA 23) is a systemic pesticide, primarily for immature stages and is also best used preventatively. This season, some growers applied Kontos (spirotetramat), early as a soil drench with good results. (It’s too late now). Although systemic, Kontos is very water insoluble and slow acting. As a rule, insecticide drenches tend to be long-lasting (4 to 6 weeks).
Differences in cultivars, culture and environmental conditions may increase or decrease bract sensitivity to pesticides and unlike lower leaves, which can be removed, bracts need to remain and appear ‘perfect’ at sale. If you are inexperienced with using a particular pesticide, always test a small portion across varieties before treating your entire crop. Be sure to follow label directions exactly. See the company's website to read any technical bulletins about the product or call the company's technical representative before using a product for the first time.
After the poinsettia season is over, be sure to thoroughly clean your greenhouse: remove all poinsettias and weeds so the whiteflies do not have host plants to feed on. Careful attention to proper sanitation is needed to prevent whiteflies from becoming established on spring plants.
Photos: Tips on Scouting Poinsettia Insect and Mite Pests, Leanne Pundt, UConn Extension (slide show, pdf) shows photos of whitefly stages, parastized whitefly etc.
Photos (many) and information: Bemisia, Lance S. Osborne, University of Florida
Tina Smith, UMass Extension and Leanne Pundt, UConn Extension