Management of Sweetpotato Whiteflies on Poinsettias With Ventigra^TM and Velifer^TM Insecticides as a Rotation or Solo Application

The purpose of this study was to assess relative efficacy of Ventigra and Velifer insecticides in managing whiteflies on greenhouse-grown poinsettias, as part of an insecticide rotation or as a solo application. The trial was conducted between Sep 3 and Oct 15 (2019) in the IPM greenhouse at the Texas A&M AgriLife Research & Extension Center in Overton, TX. Poinsettias were artificially infested with whitefly by covering all the potted plants under row cover (Row Cover Deluxe; Greenhouse Megastore, Danville, IL) and releasing 2 adults (average) per plant per week on two consecutive weeks (Aug 19 and Aug 26) into the plant enclosure. On Sep 3, counts of the number of whitefly nymphs and pupae per leaf were made non-destructively by visual inspection using a 3.5× head magnifying lens. All leaves on each plant were inspected and adults removed from plants. Treatments were assigned to experimental units in a CRD with seven replications per treatment, with one replicate constituting of one poinsettia plant inside a 47.5 × 47.5 × 47.5 cm netted observation cage (44545F; MegaView Science Co., Ltd., Talchung, Taiwan). All insecticide treatments were made as foliar sprays using an R&D CO₂ sprayer (Model D-203S) fitted with a 601FA single nozzle spray boom (Bellspray, Inc., Opelousas, LA) and sprayed until runoff (Table 1).

The number of whitefly immatures (nymphs and pupae), adults, and dead immatures were sampled from a single tagged leaf per plant using visual counts at 0, 7, 14, 28, and 42 days after the first spray application. Phytotoxicity and pesticide residue were also rated from 0 (no phytotoxicity/no residue) to 10 (high phytotoxicity/highly visible residue) during each sampling date. Differences between treatment means were compared separately for each DAT using ANOVA on log-transformed data and Tukey’s Honest Significant Difference (HSD) for multiple comparisons.

All Velifer and Ventigra treatments (individually or in a rotation) provided significant suppression of whitefly immatures and adults by 28 DAT compared to the untreated check (Tables 2 and 3), with up to 100% suppression in some treatments, such as Velifer 13 fl. oz. / 100 gal. Botanigard 22WP provided significant suppression of immatures by 28 DAT (Table 2) and whitefly adults by 14 DAT (Table 3) compared to the untreated control. Further inspection of poinsettias at 42 DAT provided additional support for excellent control of whitefly immatures on Ventigra treatments alone or in rotation with Velifer (data not shown). Applications of Velifer were at least equivalent to Botanigard 22WP in suppression of immatures and adults on poinsettias when applied weekly for three times. No signs of phytotoxicity or insecticide residue were observed for the duration of the trial.¹

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