Neil A. Spomer

Bioavailability of Chlorantraniliprole and Indoxacarb to Eastern Subterranean Termites (Isoptera: Rhinotermitidae) in Various Soils

ARSTRACT A laboratory study was conducted to determine the toxicity of indoxacarb and chlorantraniliprole to Eastern subterranean termites, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) resulting from topical applications and exposure to treated soil. Soils with varying organic matter (0.57–3.64%) and chemical characteristics were used in termiticide bioassays. Lethal dose resulting from topical application indicated that chlorantraniliprole was two- to 11-fold more toxic than indoxacarb. Lethal concentration assays yielded opposite results where concentrations of indoxacarb in soil that caused either 50 or 90% mortality of R. flavipes workers at 48 and 144 h were two- to six-fold lower than chlorantraniliprole. The bioavailability of indoxacarb and chlorantraniliprole was negatively correlated with soil organic matter. Our results suggest that indoxacarb is more bioavailable to termites in soil than chlorantraniliprole based on calculated bioavailability ratios. However, how these laboratory results correlate to actual field application data and termite efficacy is unknown, and more research is needed. These compounds seem to have excellent activity on termites and have potential to provide new modes of action and new chemistry as liquid termiticides.

Influence of Temperature on Rate of Uptake and Subsequent Horizontal Transfer of [14C]Fipronil by Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract The effect of temperature on [14C]fipronil uptake and transfer from donor (D) to recipient (R) Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) workers was evaluated. Test chambers used in the fipronil uptake study were constructed from petri dishes containing autoclaved soil treated with 1 ppm [14C]fipronil (1.14 μCi of total radioactivity per petri dish), distilled water, and R. flavipes workers. Test chambers were held in environmental growth chambers preset at 12, 17, 22, 27, and 32°C. For the fipronil transfer study, donor termites stained with Nile blue-A were exposed to soil treated with 1 ppm [14C]fipronil for 2 h. Donors were then combined with unexposed recipient termite workers at either 1D:5R, 1D:10R, or 1D:20R ratios. Test chambers consisted of a nest and feeding chamber connected by a piece of polyethylene tube and held in growth chambers at 12, 17, 22, 27, and 32°C. Worker termites were sampled over time and the amount of [14C]fipronil present was measured by scintillation counting. Some degree of uptake and transfer occurred at all temperatures and ratios in this study. The highest level of uptake occurred by termites held at 22–32°C, followed decreasingly by 17 and 12°C. Maximum transfer of [14C]fipronil occurred at the higher ratios (1:5 > 1:10 > 1:20) of donors to recipients. Data presented in this study suggest that temperature is one of the key factors affecting the rate of uptake and subsequent horizontal transfer of [14C]fipronil in subterranean termites.

Temporal changes in chlorantraniliprole and indoxacarb in four midwestern soils and bioefficacy against the eastern subterranean termite (Isoptera: Rhinotermitidae).

ABSTRACT Temporal changes in indoxacarb and chlorantraniliprole were determined in four midwestern soils by simulating commercial field applications of termiticides. Indoxacarb (0.0625 and 0.125%) and chlorantraniliprole (0.05 and 0.10%) were applied to each soil type in a rotating cement mixer to ensure uniform distribution of active ingredient (AI). Temporal and spatial changes in termiticide concentrations were determined by sampling soil cores subdivided at different depths (0–20, 20–40, and 40–61 cm) at various intervals up to 705 d after application. Percentage loss of indoxacarb was initially greater (0–180 d) than losses after 180 d. The lowest indoxacarb extractable concentrations were detected in soils closest to the surface. Chlorantraniliprole losses with time from all soils were slower than indoxacarb, with no differences observed with soil type or depth. Bioefficacy was evaluated in laboratory glass tube bioassays that monitored the distance of termite penetration into treated soils and resulting eastern subterranean termite, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), worker mortality. Bioassay data revealed that R. flavipes termites were unable to completely penetrate 50 mm of indoxacarb- and chlorantraniliprole-treated soils at 0 d after treatment; however, termites were not deterred from foraging in these soils indicating no repellency to these termiticides. Termites completely penetrated (50 mm) soils treated with indoxacarb (0.0625%) by 360 d and complete penetration occurred in all soils treated with indoxacarb (0.0625 and 0.125%) by 705 d. Termites were unable to completely penetrate chlorantraniliprole-treated soils at 705 d. Mortality of termite workers was high in all chlorantraniliprole-treated soils at all sampling intervals. These data confirm that vertical differences in termiticide persistence occur in various soils.

Temperature Effect on Kinetics of Uptake, Transfer, and Clearance of [14C]Noviflumuron in Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract [14C]Noviflumuron uptake, clearance, rate of excretion, and transfer from treated to untreated termite workers were evaluated at 15, 19, 23, and 27°C. Feeding units were constructed from plastic containers provisioned with washed sand, distilled water, [14C]noviflumuron-treated feeding discs (0.05 or 0.5% [AI]), and Reticulitermes flavipes (Kollar) workers. Feeding units were held in environmental growth chambers preset at 15, 19, 23, and 27°C. The amount of [14C]noviflumuron present within R. flavipes was measured by scintillation counting and subsequently quantified. Uptake of noviflumuron by R. flavipes workers at 15°C was ≈2.8 times less than at 19 or 23°C and ≈4.4 times less than at 27°C. The highest uptake of [14C]noviflumuron occurred at 27°C and 144 h. Most transfer of [14C]noviflumuron from treated to untreated termite workers occurred between 19 and 27°C. [14C]Noviflumuron had a half-life in R. flavipes workers of ≈31–45 d, dependent on temperature. A higher amount of [14C]noviflumuron was lost through excretion at ≥19°C (≈15–22%) compared with 15°C (0.27%). Results indicated that increased uptake, transfer, and clearance of noviflumuron by R. flavipes occurred at warmer temperatures (19–27°C), and all of these processes were significantly lower at 15°C.