Field efficacy of isocycloseram (plinazolin technology sc200), a new insecticide product for control of diamondback moth in cabbage in Southern California, 2024

We conducted a field experiment at the UC ANR Hansen Agricultural Research and Extension Center in Camarillo, CA, to evaluate the efficacy of a new foliar insecticide for the management of diamondback moth (DBM) larvae feeding on cabbage. The new foliar insecticide (PLINAZOLIN Technology SC200, isocycloseram), a broad-spectrum local standard (Radiant SC, spinetoram), and an untreated control were evaluated. Each bed was assigned 1 of these 3 treatments in an RCB design with 4 blocks with each treatment replicated per block. Cabbage ‘Supreme Vantage’ transplants were planted by hand on 6 Aug on beds (36-inch center-to-center). In each bed, 2 cabbage rows were planted, and plant spacing within a row was 1.5 ft. The experimental area included 12 beds total; each bed was 27 ft long with ~36 plants/bed. Beds were separated by 22-inch furrows.

The insecticide treatments were applied on 19 Aug and 5 Sept using a CO₂-pressurized backpack sprayer (BellSpray Inc.) with a boom equipped with 2 nozzles (5500-X1 Adjustable Cone Jet Tip) spaced 24 inches apart. The sprayer was calibrated to deliver a volume of 30 GPA at 40-60 PSI, and all insecticide treatments were applied in water with the nonionic surfactant Dyne-Amic at 0.25% (v:v). The control treatment did not receive any treatment.

The experimental area was sampled before and after each insecticide application for DBM larvae. Pretreatment evaluations were conducted 6–18 h prior to application, and posttreatment evaluations were carried out at 2, 7, and 14 DAA. For each evaluation, we randomly selected 10 plants in each treatment and assessed the number of DBM larvae in each plant. We also conducted an additional evaluation at 21 DAA after the second pesticide application. For each plant observed during the experiment, every leaf was inspected for live DBM larvae.

We compared levels of DBM larvae across the three treatment groups prior to each application and at 2, 7, and 14 DAA. We additionally compared DBM larvae counts between treatments at 21 DAA for the second application. We checked the assumption of normality with a Shapiro–Wilk test and the assumption of homogeneity of variances with a Levene’s test. Because the DBM count data violated these assumptions, we compared DBM levels across treatment groups using Kruskal–Wallis tests. To determine which groups differed significantly, we used Dunn’s test with adjusted P-values for multiple comparisons. All analyses were performed in R.

Prior to the first application, the DBM infestation level was 0.37 DBM larvae/plant and there were no significant differences between treatments. There were significant differences between treatments of DBM larvae counts at every sampling period after the 2 applications (Tables 1 and 2). The PLINAZOLIN technology SC200 treatment exhibited significantly lower DBM counts compared to the untreated check at each of the sampling periods after both applications. It also exhibited significantly lower DBM counts compared to the conventional control (Radiant SC) at each of the sampling periods after each application, except for 2 DAA after the first application. The conventional standard treatment (Radiant SC) exhibited significantly lower DBM counts compared to the untreated check only at 2 DAA after the first application.

Across posttreatment sampling dates, the PLINAZOLIN technology SC200 treatments (2.1 fl oz/acre) suppressed DBM larvae infestation by a minimum of 56.8% (21 DAA, Spray 1) and a maximum of 90.5% (2 DAA, Spray 2) compared to the untreated control. The Radiant SC treatments (10 fl oz/acre) suppressed DBM larvae infestation by a minimum of 12.7% (2 DAA, Spray 2) and a maximum of 71.43% (2 DAA, Spray 1) compared to the untreated control. At 7 and 14 DAA for Spray 1 and 21 DAA for Spray 2, Radiant SC failed to suppress infestation entirely, and on average, DBM larvae counts were greater compared to the control. The results of this field experiment suggest that foliar applications of PLINAZOLIN technology SC200 can provide higher control of DBM larvae than the commercial standard spinetoram (Radiant SC) or untreated control.¹

Footnotes