Optimizing a Basal Bark Spray of Dinotefuran to Manage Armored Scales (Hemiptera: Diaspididae) in Christmas Tree Plantations

Abstract

The armored scales Fiorinia externa Ferris and Aspidiotus cryptomeriae Kuwana (Hemiptera: Diaspididae) are increasingly damaging to Christmas tree plantings in southern New England. The systemic insecticide dinotefuran was investigated for selectively suppressing armored scale populations relative to their natural enemies in cooperating growers' fields in 2008 and 2009. Banded soil application of dinotefuran resulted in poor control. However, a dinotefuran spray applied to the basal 25 cm of trunk resulted in its absorption through the bark, translocation to the foliage, and good efficacy. The basal bark spray did not significantly impact the activity of predators Chilocorus stigma (Say) or Cybocephalus nipponicus Enrody-Younga and in 2009 showed a dosage-dependent improvement in the percentage of scales parasitized by Encarsia citrina Craw. A field dosage-response factorial experiment revealed that a 0.25% (vol:vol) addition of a surfactant with dinotefuran did not enhance insecticidal effect. Probit-transformed scale population reduction relative to the untreated check was subjected to linear regression analysis; reduction of scale populations was proportional to the log of insecticide dosage, whereas basal bark spray efficacy declined in proportion to the cube of tree height. The regression equation can be used to optimize dosage relative to tree height. Excellent efficacy resulted from basal bark spray application dates of 28 April (prebud break) to mid-June, but earlier spray timing within that treatment window had fewer crawlers discoloring new growth with their short-lived feeding. A basal bark spray of dinotefuran is well suited for integration with natural enemies to manage armored scales in Christmas tree plantations.

Coccinellids in Biological Control

“…Another systemic neonicotinoid, dinotefuran, was shown to provide good control of armored scales on Christmas trees when applied in a band around the base of the trunk, without impacting the foraging activities of the scale predators Chil. stigma and Cybocephalus nipponicus (Cowles 2010 ). However, coccinellids can be impaired behaviourally or reproductively by non -lethal concentrations of insecticides that they may acquire when feeding on contaminated pollen or nectar (Smith & Krischik 1999 ) or contaminated prey (Singh et al 2004, Eisenback et al 2010.…”

Interactions of Light Intensity, Insecticide Concentration, and Time on the Efficacy of Systemic Insecticides in Suppressing Populations of the Sweetpotato Whitefly (Hemiptera: Aleyrodidae) and the Citrus Mealybug (Hemiptera: Pseudococcidae)

“…Insecticides with higher water solubilities tend to be more mobile within the plant. Therefore, the low solubility of imidacloprid may impede movement throughout plant tissues (Hale andShorey 1965, Tomlin 1994), particularly in woody plants as woody plant stems may inhibit the concentration of active ingredient that reaches and accumulates within plant leaves although this may vary depending on plant type, developmental stage, and the particular systemic insecticide (Cowles 2010). Both yellow sage and poinsettia develop woody tissue (Liberty Hyde Bailey Hortorium 1976), particularly later in the production cycle, which may delay the movement of imidacloprid throughout the plant.…”

Imidacloprid Bark Treatment for Hemlock Woolly Adelgid (Adelges tsugae)

“…These results are not suprising for many reasons. Imidacloprid is one of several neonictinoids that are water soluable and have been proven (as a class of insecticides) to work as a basal bark spray providing sufficient insecticide concentrations for bark penetration and suffecient insect mortality (Cowles 2010). It is the water solubility that, at least in part, dictates the penetrating abilities of a chemical.…”

“…Dinotefuran and acetamiprid are approved for bark applications. Dinotefuran works rapidly and even treats elongate hemlock scale, another serious pest of eastern hemlock (Cowles 2010). Suppression of HWA is reported to be from 79% to 87% one month after application (Joseph et al 2011).…”

“…Systemic neonicotinoids on the whole are a suspected cause. In the U.S. local, state, and federal decision makers are taking precautions to protect pollinators from neonicotinoids (Cowles 2010). It should be noted that the cause of CCD is still unknown (USDA 2012).…”