Washington State University
Vancouver Research and Extension Unit
Vancouver, WA 98665-9752
Website: vancouverreu.wsu.edu
Bamboo spider mites, Stigmaeopsis celarius Banks (Schizotetranychus celarius) live in protected web nests and are difficult to control. Current recommendations are limited and do not reflect the new acaricide chemistries. Eight acaricides with and without the organosilicone surfactant, Silwet (a total of sixteen tests), were evaluated for bamboo spider mite control against young, thinly webbed colonies and older heavily webbed colonies. Efficacy of the organosilicone surfactants, Silwet and Sylgard were compared.
Mite infested leaves were collected from an ornamental planting of Dragon’s head bamboo, Fargesia dracocephala from Portland, Oregon, 19 July 2005. Bioassays were performed using a leaf dip technique. Small twigs of bamboo with mite-infested leaves were inserted into a water-filled, small dram, shell vials and plugged with cotton. One leaf/vial was selected and the remaining leaves were removed. Selected leaves were infested with one or more web nests. Each web nest represented a single colony or replicate. The twigs were laid horizontally on water-dampened cotton pads situated in trays. Young colonies appeared translucent with at least one motile mite visible beneath the webbing, while older colonies were opaque. Only motile stages, adults, nymphs, and larvae were evaluated.
Ten replicates were prepared for the water treated check and for each of three tests: miticides, miticides with surfactants added, surfactants alone. Leaves were dipped for two seconds into the solutions and treated checks were dipped into distilled water. After dipping, the vials were returned to the trays. Colonies were scored as alive or dead based on the presence or absence of motile mites at one, two, and three-day intervals.
After 24 hours, Avid (abamectin), Mesa (milbemectin), Sanmite (pyridaben) and Talstar (bifenthrin), all provided complete control alone and with the addition of Silwet (Table 1). In contrast Floramite (bifenazate) and Vendex (fenbutatin-oxide) provided the weakest control after 24 hours. The addition of Silwet to Kanemite (acequinocyl) and Floramite improved their performance by 30% and 50% respectively, after 24 hours. Three days following treatment, only Kanemite failed to reach 100% mortality.
When mite colonies were treated with the surfactants Silwet and Sylgard, without the benefit of a miticide, each treatment exhibited a surprising 90% mortality at 1 DAT and complete control after three days. These results provide additional options for specialty bamboo growers.
| Treatment | Product (amt/100 gal) | Percent mortality | ||
|---|---|---|---|---|
| 1DAT | 2DAT | 3DAT | ||
| Means within columns followed by the same letter are not significantly different (Tukey HSD test P<0.05). | ||||
| Avid 0.15EC | 4 fl oz | 100d | ||
| + Silwet | 100d | |||
| heavy nests | 100d | |||
| Floramite 50WP | 4 oz | 50b | 90b | 100c |
| + Silwet | 100d | |||
| heavy nests | 100d | |||
| Kanemite 15WC | 32 fl oz | 70bcd | 90b | 90b |
| + Silwet | 100d | |||
| heavy nests | 100d | |||
| Mesa EC | 12.8 fl oz | 100d | ||
| + Silwet | 100d | |||
| heavy nests | 100d | |||
| Sanmite 75WP | 4 oz | 100d | ||
| + Silwet | 100d | |||
| heavy nests | 100d | |||
| Talstar 10WP | 16 oz | 100d | ||
| + Silwet | 100d | |||
| heavy nests | 100d | |||
| Tame 2.4EC | 16 fl oz | 100d | ||
| + Silwet | 80bcd | 90b | 100c | |
| heavy nests | 100d | |||
| Vendex 50WP | 16 oz | 60bc | 80b | 100c |
| + Silwet | 70bcd | 80b | 100c | |
| heavy nests | 90cd | 100b | ||
| Silwet L-77 | 4 fl oz | 90cd | 80b | 100c |
| Sylgard | 4 fl oz | 90cd | 100b | |
| Treated check I | 0a | 0a | 0a | |
| Treated check II | 0a | 0a | 0a | |