Elsevier

Crop Protection

Volume 29, Issue 5, May 2010, Pages 429-434
Crop Protection

Insecticide resistance in Bemisia tabaci biotype Q (Hemiptera: Aleyrodidae) from China

https://doi.org/10.1016/j.cropro.2009.10.001Get rights and content

Abstract

Dispersion of invasive biotypes of the tobacco whitefly, Bemisia tabaci, has led to protracted crop protection constraints in numerous countries over recent decades. These polyphagous, highly efficient vectors of plant viruses present an intractable problem as they frequently carry a diverse suite of insecticide resistance mechanisms. In many areas of China, native biotypes have been supplanted by the invasive and globally widespread biotype B since the 1990s. More recently, biotype Q has established, posing a new and more potent threat to agricultural production systems throughout the country. Insecticide resistance profiles for a range of Chinese B. tabaci strains covering biotypes B and Q were examined, to establish the potential for insecticides to play a pivotal role in biotype competition and ultimate displacement. Commonly used compounds including pyrethroids, neonicotinoids, abamectin and pyriproxyfen were targeted as widespread use is pre-requisite to drivers of population dynamics on a national scale.

It was found that across several strains, both biotypes responded similarly against pyrethroids, abamectin and pyriproxyfen. However, their responses to three commercially available neonicotinoids were consistently contrasting. Biotype B strains remained largely susceptible to acetamiprid, imidacloprid, and thiamethoxam, whereas biotype Q strains expressed 20–170 fold resistance to these insecticides. It appears that in China the use of neonicotinoid insecticides has the potential to select for biotype Q within mixed biotype areas, contributing to the establishment and prevalence of this relatively recent introduction.

Introduction

The tobacco whitefly, Bemisia tabaci (Gennadius), is considered a taxonomically complex and intractable pest of vegetable, ornamental and commodity crops (Brown et al., 1995, Denholm et al., 1998). Conventional practice is to divide the species into biochemically distinct but morphologically inseparable biotypes, two of the most prevalent being biotype B and biotype Q. Biotype B is distributed throughout the world, following a dramatic expansion in range that commenced in the late 1980s (Guirao et al., 1997, Rosell et al., 1997). Biotype Q, which is thought to originate from the Iberian Peninsula (de la Rua et al., 2006), has spread throughout the Mediterranean region and has more recently become established in China (Chu et al., 2006), Japan (Ueda and Brown, 2006), Mexico (Martinez-Carrillo and Brown, 2007), the USA (Boykin et al., 2007) and New Zealand (Scott et al., 2007). Both biotypes exhibit broad host ranges, rapid population growth, and a marked ability to develop strong resistance to insecticides (Horowitz et al., 2005).

B. tabaci was first recorded in China in 1949 (Zhou, 1949) but was not considered a significant pest until the 1990s (Xu, 1996). Since then biotype B has been found to be widely distributed in China on vegetable and cotton crops (Luo et al., 2002, Wu et al., 2002, Qiu et al., 2007, Ma et al., 2007). Following suspected importation on ornamental plants, biotype Q was first found in China in 2003 (Chu et al., 2005, Zhang et al., 2005) and subsequently in new regions in 2004 (Chu et al., 2006). A further infestation of biotype Q occurred at the 2006 Shenyang International Horticultural Show (Fang et al., 2008). The exact contemporary distributions of biotypes B and Q remains unclear but it is known that Q has substantially supplanted B on outdoor crops in Hubei province (Qiong Rao, unpublished data), where reported crop losses due to B. tabaci in 2007 were in excess of US$ 600 million (data supplied by Hubei Plant Protection Service, 2008).

Insecticides are the primary means of controlling B. tabaci in China and resistance is a constant threat. Resistance can be selected de novo through over-reliance on particular chemicals or, more perversely, may already be present when pests invade new cropping systems (Denholm et al., 1998). This is a particular concern with biotype Q, which shows a frequent association with resistance to IPM-compatible insecticides including neonicotinoids and the juvenile hormone analogue, pyriproxyfen (Horowitz et al., 2005). We report here for the first time on resistance profiles of biotype Q insects collected in China, compare these with contemporary biotype B collections, and discuss the implications for biotype dynamics and the potential displacement of one biotype by another.

Section snippets

B. tabaci strains

Five samples of B. tabaci were collected in 2007/2008 from Xinjiang (XJ), Beijing (BJ), Zhejiang (ZHJ), Jiangsu (JS) and Hubei (HB) provinces (Fig. 1). Each consisted of numerous leaves collected at random from the crop canopy, containing a minimum of 100 adults or nymphs per sample. Of the compounds tested, the neonicotinoids (imidacloprid, thiamethoxam and acetamiprid), pyrethroids (cypermethrin, bifenthrin) are being widely used for control of B. tabaci outbreaks on vegetable crops in China.

Biotype determination

All individuals from the biotype reference strains scored correctly. Negative controls did not induce fluorescence of either reporter dye; positive controls demonstrated differential fluorescence rates. Biotypes B and Q positive controls increased fluorescences of VIC and FAM reporter dyes, respectively. All individuals from the five Chinese strains fell unambiguously into one of two clusters on a bivariate scatter graph (Fig. 2). All the strains were single biotype, i.e. different biotypes

Discussion

Factors influencing the invasiveness and subsequent establishment of biotypes of B. tabaci are likely to be complex and dependent, in large part, on regional differences in climate, cropping systems and control practices. In China, the appearance and spread of biotype B in the late 1990s led to a substantial expansion in the geographical and host ranges of B. tabaci, and in its status as an agricultural pest. Use of insecticides against this species increased accordingly with strong reliance on

Acknowledgements

We thank colleagues from the Beijing Academy of Agriculture and Forestry Sciences and Rothamsted Research for detailed scientific discussion. We thank National Basic Research and Development Program No.2009CB119200 and National Natural Science Foundation of China No.30400291 for funding of research in China, and Dr. Shusheng Liu and Dr. Yuanxi Li for providing insect samples. Chen Luo acknowledges receipt of a Rothamsted International Fellowship. Rothamsted Research is an institute of the

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