Laboratory evaluation of the effects of triflumuron on the development of Rhodnius prolixus nymph

Abstract

Studies were carried out to evaluate the efficacy of the growth regulator, triflumuron (TFM) (Starycide ® sc 480 Bayer), for disrupting the development of Rhodnius prolixus fifth-instar nymph by oral, topical or continuous treatment. All treatments were able to induce high levels of mortality, delay development and molt inhibition. Oral treatment induced molt inhibition in all insects that survived at doses of 0.25, 0.50 and 5.0 mg/mL of a blood meal. The highest levels of both mortality in 24 h and molt inhibition were always observed after topical treatment. The lowest doses needed to obtain considerable biological effects were always observed after continuous treatment. In this way, the highest levels of mortality within 30 days were detected after continuous treatment, which also induced an extended inter-molting period, a lower number of over-aged nymphs and the highest level of molting in nymphs that survived. Moreover, the effects of TFM on insects were often displayed in a dose response manner. These results indicate that TFM acts as a potent growth inhibitor of R. prolixus nymphs and has the potential to be used in integrated vector control programs against hematophagous triatomine species.Key words: Rhodnius prolixus -triflumuron -benzoylphenylurea -chitin synthesis inhibitorIn search of alternative methods against insect pests that would avoid the harmful effects of conventional insecticides on both the environment and human health (WHO 2006), the insect growth regulators (IGRs) of the benzoylphenylurea (BPU) family were used against a wide range of crop, pasture and forest pests (Amir & Pevelling 2004) and also against disease vectors (Langley 1995, Rehini & Soltani 1999, Senthil-Nathan et al. 2006. The primary mode of action of BPUs is to disrupt chitin synthesis during larval development, which is the period that determines molting inhibition and/or malformations of the cuticle (Merzendorfer 2006). Since BFUs are relatively selective towards immature life stages of arthropods and are safe for vertebrates, they are often preferred over broad-spectrum insecticides when control operations against agricultural plagues are conducted in natural and semi-natural ecosystems (Sulaiman et al. 1994).Chagas disease (Chagas 1909) is an illness widely spread in South America that currently affects 18 million people (Garcia et al. 2007) by the dissemination by hematophagous insects such as Rhodnius prolixus. Furthermore, R. prolixus is traditionally used as a model for studies of insect physiology, control vector strategies and parasite vector interactions (Garcia & Azambuja 2004). Therefore, the aim of the present work was to investigate the biological effects of different doses and treatments , containing 48 g of TFM per 100 mL, was kindly provided by Bayer (Brazil) and directly used for the experiments using fifth-instar nymph of male R. prolixus (Hemiptera: Reduviidae). The insects were reared and maintained in the laboratory at 28 o C with a relative humidity of 60-70%, as described by Garcia et al. (...

Triflumuron Effects on the Physiology and Reproduction ofRhodnius prolixusAdult Females

“…Our data obtained with adult females of R. prolixus corroborate previous observations, showing that TFM is able to induce high levels of mortality after treatment [32]. Regardless of the putative differences in the chitin metabolism between male nymphs [32] and adult females (present work), we registered similar mortalities among these groups.…”

“…We previously confirmed the effectiveness of triflumuron (TFM) against R. prolixus nymphs [32]. The aim of this work is to extend these studies and determine the biological and physiological effects of TFM (Starycide® sc 480 Bayer) on R. prolixus adult females.…”

“…Adult females of Rhodnius prolixus were reared in laboratory conditions at 28°C and relative humidity of 60–70% [32]. Randomly chosen insects were then allowed to feed upon a membrane apparatus [33] and submitted to biological assays (see Section 2.3).…”

Effect of the chitin synthesis inhibitor triflumuron on the development, viability and reproduction of Aedes aegypti

“…aegypti (Vasuki 1992), suggesting subtle variations among different CSIs. Triflumuron diminished the longevity of the triatomine Rhodnius prolixus when administered by contact, blood ingestion or injection (Mello et al 2008). The coleoptera Tenebrio molitor exposed to the CSI diflubenzuron also exhibited reduced longevity (Soltani et al 1983).…”

Development of an insecticidal nanoemulsion with Manilkara subsericea (Sapotaceae) extract

“…Untreated insects received no treatment, being only fed. Biological evaluation was performed in order to determine mortality levels during the entire time required for development from the fourth instar to the adult stage [9,33,34]. All experiments were repeated at least three times with samples from 30 insects ( n  = 30 in each triplicate).…”