Efficacy of Insecticides for Control of Aphelenchoides fragariae and Ditylenchus dipsaci in Flowering Perennial Ornamentals.

The effects of abamectin B1, diazinon, and methiocarb insecticides on Aphelenchoides fragariae and Ditylenchus dipsaci in Lamium maculatum, Phlox subulata, Rhododendron indicum, and Begonia x tuberhybrida were determined in a series of greenhouse experiments. Abamectin at 0.005 or 0.011 g a.i./liter (0.3 or 0.6 ml/liter Avid 0.15 EC), diazinon at 0.62 or 1.87 g a.i./liter (2.6 or 7.8 ml/liter KnoxOut GH), or methiocarb at 3.5 g a.i./liter (4.7 g/liter Mesurol) were applied in two to six weekly or biweekly applications to foliage until runoff. Diazinon and abamectin reduced both A. fragariae and D. dipsaci populations in Lamium and Phlox, especially after repeated applications. Diazinon was generally more effective than abamectin. While methiocarb reduced A. fragariae densities in Lamium, it was not as efficacious as diazinon or abamectin. Nematode populations varied widely between host plant species and over time. Management of high nematode populations was difficult, and none of the materials tested was effective against A. fragariae in azalea or begonia. Both abamectin and diazinon are currently registered for insect control in ornamentals and may be combined with cultural control tactics to manage foliar nematodes.