Alternatives to a pyrethroid for controlling Madeira mealybug (Hemiptera: Pseudococcidae) on coleus cuttings
Keywords:
insecticide dips, nursery, Mavrik Aquaflow®, biorational productsAbstract
Mealybugs (Hemiptera: Pseudococcidae) are soft-bodied insects that infest a variety of ornamental plants, and early instars are almost undetectable to the human eye. Because the cryptic mealybugs can cause significant damage quickly, plant cuttings often are preventively dipped into pyrethroid-based insecticides. Dips differ widely, however, in their phytotoxicity, effectiveness in killing mealybugs, and operational efficiency and cost. Therefore, to assess the efficacy of alternative dips, tests were conducted on biorational products for controlling the Madeira mealybug, Phenacoccusmadeirensis Green, on coleus plants, Plectranthus scutellarioides, var. ‘Big Red Judy’ L. (Lamiaceae). Initially, phytotoxicity was evaluated using different concentrations and exposure times for dips containing Natur’l oil, dish detergent, Wetcit®, or Vapor Gard®. The highest concentrations of these products for which phytotoxicity could be tolerated were 1%, 1%, 0.1%, and 0.1%, respectively, in 30 s dips. Based on the results, these concentrations were used in dips to evaluate their effectiveness in eliminating mealybugs. The most effective biorational product, Natur’l oil, then was compared with the commercial standard synthetic pyrethroid, Mavrik Aquaflow® (22.3% tau-fluvalinate). Both products killed > 90% of the nymphs within 14 d when applied as a 1% aqueous mixture for 60 s. Thus, Natur’l oil could be used instead of the pyrethroid as a dip to remove Madeira mealybugs from coleus cuttings.
Resumen
Las cochinillas son insectos de cuerpo blando que infestan una gran variedad de plantas ornamentales, los estadios tempranos de estos insectos son casi imperceptibles para el ojo humano. Las inmersiones de plantas en insecticidas que contienen piretroides sintéticos son utiliadas a menudo en un intento de matar cochinillas crípticas y prevenir daños las plantas. Las inmersiones difieren ampliamente en su fitotoxicidad, efectividad en eliminar cochinillas, eficiencia operacional y costo. Por lo tanto, para evaluar la eficacia de las inmersiones alternativas, se realizaron pruebas en productos bioracionales para controlar el piojo harinoso, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae), en plantas de coleo, Plectranthus scutellarioides, var. ‘Big Red Judy’ L. (Lamiaceae). Inicialmente, se evaluó la fitotoxicidad utilizando diferentes concentraciones y tiempos de inmersión en soluciones o emulsiones con aceite natural “Natur’l oil”, detergente para platos, Wetcit® o Vapor Gard®. Las concentraciones más altas de estos productos en las cuales se tolera fitotoxicidad fueron 1%, 1%, 0.1%, y 0.1%, respectivamente, a un tiempo de inmersión de 30 s. Basados en estos resultados, estas concentraciones fueron utilizadas en inmersiones para evaluar la efectividad eliminando piojos harinosos El producto bioracional más eficaz, fue el aceite natural Natur’l oil que se comparó con el piretroide sintético comercial, Mavrik Aquaflow® (22,3% tau-fluvalinato), y ambos mataron a más del 90% de las ninfas cuando se aplicaron como mezcla acuosa al 1% por 60 s. Por lo tanto, el aceite natural “Natur’l oil” puede ser utilizado en lugar del piretroide sintético en inmersión para eliminar las cochinillas en los esquejes de coleo.
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