Feeding cessation after feeding on 20-hydroxyecdysone in the Formosan subterranean termite.

BACKGROUND: To control subterranean termite pests, chitin synthesis inhibitor (CSI) baits have been widely applied. Despite CSI baits having low impacts on the environment, they require a lengthy time period to eliminate colonies. 20-hydroxyecdysone (20E) was proposed to speed up the baiting process as it showed faster mortality than CSI baits. However, the efficacy of 20E has previously not been tested at the colony level prior to applying in the field. RESULTS: We compared the effect of 20E, 20E + noviflumuron, noviflumuron and untreated control using colonies of Coptotermes formosanus. Our result revealed that both 20E and 20E + noviflumuron did not accelerate colony elimination and termite activity remained relatively stable during the observation periods. To determine the limited effects of 20E, we further investigated feeding duration and consumption amount of 20E with different concentrations (control, 100 and 1000 ppm) for 10 days. Termites ceased feeding after 1 day in 100 and 1000 ppm treatment and 100% mortality was observed within 10 days in 1000 ppm 20E, while mortality in the 100 ppm 20E treated group was much lower than that in the 1000 ppm group. Furthermore, no termites molted in the control and termites died from hyperecdysonism in 1000 ppm 20E treatment, whereas about 20% of termites molted in 100 ppm 20E. CONCLUSION: This study demonstrated that 20E may not be suitable as a sole active ingredient to accelerate elimination of a subterranean termite colony, while CSI baits and lower concentrations of 20E may reduce the lengthy time period in colony elimination. © 2023 Society of Chemical Industry.

Concentration-Dependent Feeding Deterrence to 20-Hydroxyecdysone for Three Subterranean Termite Species (Blattodea: Rhinotermitidae).

Effective active ingredients in toxicant bait formulations must be non-deterrent to insect feeding behavior at lethal concentrations. This study evaluated feeding deterrence for Coptotermes formosanus Shiraki, C. gestroi (Wasmann), and Reticulitermes flavipes (Kollar) when provided access to cellulose impregnated with various concentrations of the insect molting hormone, 20-hydroxyecdysone (20E). Termites were exposed to 20E concentrations of 200, 500, 1000 and 2000 ppm and to noviflumuron at 5000 ppm in a 24 h choice-test, and the mass of substrate consumption from treated and untreated media pads was compared for each treatment. 20E feeding deterrence was detected at 500, 1000 and 2000 ppm for C. gestroi, and at 2000 ppm for C. formosanus. No significant differences in consumption of treated and untreated substrate was detected at any concentration for R. flavipes. Potential methods for reducing deterrence are discussed.

Mortality Time Trends of Three Subterranean Termite Species When Exposed to 20-Hydroxyecdysone, Alone and in Combination With Noviflumuron.

Workers of three termite species, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae), and Reticulitermes flavipes (Kollar) (Blattodea: Rhinotermitidae), were force-fed with cellulose media pads treated with 20-hydroxyecdysone (20E) alone and in combination with noviflumuron for 3 d to examine their mortality time trends up to 14 d (including 3-d exposure time). Termites exhibited symptoms of hyperecdysonism before the onset of death. The times required for 20E to fully express its effects were 10-13 d for C. formosanus, 13-14 d for C. gestroi, and 11-13 d for R. flavipes. Higher 20E concentrations resulted in higher mortalities at 14 d, and the addition of noviflumuron generally yielded higher mortalities. The lethal time of 20E was similar to chitin synthesis inhibitors such as noviflumuron than metabolic inhibitors, and the 10-14 d lethal time may be sufficient for 20E-affected termites to return to the central nest before the onset of hyperecdysonism and ultimate death. As an active ingredient in baiting systems, 20E has shown potential to reduce the colony elimination time.

Tonsuritermes, a new soldierless termite genus and two new species from South America (Blattaria: Isoptera: Termitidae: Apicotermitinae).

A new genus, Tonsuritermes Cancello Constantini gen. nov., is described from South America. The main morphological features of the new genus are a remarkable frontal gland and protibia with two rows of spine-like bristles. Two new species of Tonsuritermes are described: T. tucki Cancello Constantini sp. nov. and T. mathewsi Cancello Constantini sp. nov. Comparisons, measurements, a map, histology of the frontal gland, and illustration of all fundamental morphological aspects are provided.

Laboratory and field evaluation of brown dog tick behavioral responses to potential semiochemicals.

The brown dog tick, Rhipicephalus sanguineus sensu lato (Parasitiformis: Ixodidae), is an ectoparasite of dogs that can be found worldwide. This tick poses unique difficulties in management because it can complete its entire life cycle indoors and has demonstrated acaricide resistance. The ability to monitor for tick presence and abundance is necessary for developing effective control programs. As such, an evaluation of adult brown dog tick behavioral responses to 16 potential semiochemicals was undertaken using Y-tube and straight-tube olfactometers. Both sexes of ticks were activated by nine of the 16 semiochemicals tested, including 300µg of 1-octen-3-ol, benzaldehyde, benzyl alcohol, hexanoic acid, nonanoic acid, methyl salicylate, o-nitrophenol, 2,6-dichlorophenol and salicylaldehyde. Rhipicephalus sanguineus s.l. behaviors including movement speed, direction and duration, as well as turning, were quantified following exposure to the same nine chemicals in a straight-tube olfactometer, individually at 300µg and as mixtures. Three individual chemicals, 1-octen-3-ol, hexanoic acid, and methyl salicylate induced strong responses. These three chemicals were evaluated in a semi-field setting using a modified bed bug trap but were found to provide no significant increase in attraction compared with CO2 alone. The results of these studies provide a foundation for future research regarding semiochemicals of R. sanguineus s.l.

Evaluation of Four Bed Bug Traps for Surveillance of the Brown Dog Tick (Acari: Ixodidae).

The brown dog tick, Rhipicephalus sanguineus (Latrielle), can be a serious residential pest due to its unique ability, among ticks, to complete its lifecycle indoors. A single engorged and fertilized female tick can oviposit around 4,000 eggs, allowing indoor establishment to be rapid and easy to miss in early-stage infestations. Acaricide treatment is currently the primary method of control, but can be costly and can lead to the development of acaricide resistance in tick populations. Traps of various designs can be used to help monitor and manage populations of indoor pests, such as cockroaches and bed bugs, but there are currently no commercially available traps for use with brown dog tick infestations. This study included a comparison of four commercially available bed bug traps (NightWatch [BioSensory Inc., Putnam, CT], Bed Bug Beacon [PackTite, Fort Collins, CO], ClimbUp [Susan McKnight Inc., Memphis, TN], and Verify [FMC Corporation, Philadelphia, PA]) with regard to their efficacy in capturing brown dog ticks, and also compared tick attraction to ClimbUp traps baited with several stimuli including CO2. Significantly more ticks were captured and attracted to the NightWatch and CO2-baited ClimbUp traps than the other two trap models. The results suggest that bed bug traps may be useful in brown dog tick monitoring, and CO2 will likely be an important component of a trapping system employed in the future.