Potential of Commercial Biorational and Conventional Pesticides to Manage the Ruellia Erinose Mite in Ornamental Landscapes

Abstract

Acalitus simplex is an eriophyoid mite pest of the ornamental plant Ruellia simplex. Acalitus simplex compromises the esthetics of R. simplex by inducing erinea formation. Management practices for A. simplex are currently lacking. This study assessed the potential of commercial biorational (citric acid, potassium salt of fatty acids, garlic, thyme, and mineral oil) and conventional (abamectin, fenpyroximate, bifenthrin, spiromesifen) pesticides under laboratory conditions, using two types of spray applications: (A) curative, after erinea formation, and (B) prophylactic, before erinea formation. In the curative application, abamectin, garlic oil, and mineral oil were most effective; in the prophylactic application, abamectin and mineral oil showed the highest efficacies. Abamectin and mineral oil were further tested under greenhouse conditions. Both treatments effectively controlled A. simplex by preventing erinea formation over a four-week post-application period, regardless of the application type. At the end of the experiment, mites were extracted from R. simplex plants. In the curative application, significantly fewer mites were extracted from abamectin and mineral oil treatments than in the control. In the prophylactic application, mites were absent in abamectin and mineral oil treatments but present in the control. Abamectin and mineral oil can be used to manage A. simplex in landscapes.

Keywords: Eriophyoidea; chemical control; curative application; integrated pest management; prophylactic application.

Figure 1

(a) Mean cumulative number of Acalitus simplex emerging from white erinea over time (hours) after curative applications; (b) Mean cumulative number of dead A. simplex over time after prophylactic applications. Statistically different treatments are separated with lowercase letters (N = 30 for each treatment, GLMM, p < 0.05). Gray shaded areas represent the predicted standard error, generated by R program.

Figure 2

Mean cumulative number of Ruellia simplex tissue (stems, leaves, buds and flowers) developing erinea over time (days) after (a) curative application and (b) prophylactic treatment application. Statistically different treatments are separated with lowercase letters (N = 30 for each treatment, Kruskal–Wallis, p < 0.05). Gray shaded areas represent the predicted standard error, generated by R program.

Figure 3

(a) Mean number of Acalitus simplex extracted from sprayed Ruellia simplex with curative and (b) prophylactic applications. Statistically different treatments are separated with lowercase letters (Kruskal–Wallis, p < 0.05). Error bars indicate the standard error of the mean, with N = 30 for each treatment.