One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/
B. tabaci can acquire and transmit a range of plant viruses (see Economic Impact) which produce a variety of different symptoms on susceptible plant species. Although plants can become infected from migratory feeding of B. tabaci, plants infected with B. tabaci-transmitted viruses are often indicative of B. tabaci colonization.
Infected plants could exhibit any one or a combination of the following symptoms: vein yellowing, inter-vein yellowing, leaf yellowing, yellow blotching of leaves, yellow mosaic of leaves, leaf curling, leaf crumpling, leaf vein thickening, leaf enations, leaf cupping, stem twisting, plant stunting.
Intercropping practices using non-hosts have been used in many countries aiming to reduce numbers of whiteflies on specific crops. However, intercropping with susceptible crops can promote whitefly populations, by offering more leaf area for feeding.
Weed species play an important role in harbouring whiteflies between crop plantings and attention should be paid to removing these in advance of planting susceptible crops. Weeds also often harbour whitefly-transmitted viruses (Bedford et al., 1998) and may be a major source of crop virus epidemics.
Conservation of natural enemies is important in field crops where feeding damage is the cause of losses, rather than virus transmission, for example, on cotton. Under these circumstances, attempts have been made in Israel to enhance natural enemy action on cotton by introduction of additional, hopefully more efficient parasitoids (Rivany and Gerling, 1987). This effort resulted in the establishment of two species from the USA, Encarsia luteola and a species of Eretmocerus. Similarly, parasitoids are being introduced in Florida, USA, from other regions for the control of B. tabaci on vegetables and ornamentals (Rosen et al., 1994). Predatory mites have been shown to be efficient against Mediterranean species (Cuthbertson, 2014). Entomopathogenic agents such as nematodes (Cuthbertson et al., 2003a, 2007a,b) and fungi (Cuthbertson et al., 2005a, 2012; Cuthbertson and Walters, 2005) have also been shown to be important biological tools in the control/eradication of B. tabaci.
Plant and crop species that exhibit a high level of resistance to both vector and virus must also be considered when designing an IPM system. The development of transgenic resistant plant and crop species through genetic engineering must be considered and accepted as a future method of control where whitefly-transmitted viruses are already endemic and causing severe crop losses.
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
The pest status of B. tabaci insects is complicated and through the comparison of mitochondrial cytochrome oxidase 1 (mtCO1) gene it is generally accepted that, rather than one complex species, B. tabaci is a complex of 11 genetic groups. These genetic groups are composed of at least 34 morphologically indistinguishable species, which are merely separated by a minimum of 3.5% mtCOI nucleotide divergence (Dinsdale et al., 2010; De Barro et al., 2011; Boykin and De Barro, 2014). Within the B. tabaci complex, the Middle East-Asia Minor 1 (MEAM1) cryptic species, formerly referred to as 'B' and Mediterranean (MED) cryptic species, formerly referred to as 'Q' biotype that are the two most widely distributed, and as a result, best known of the species. These two species present the greatest threat to glasshouse crops worldwide (Bethke et al., 2009). The damaging MEAM1 is described as an aggressive coloniser and is an effective vector of many viruses, whereas the MED characteristically shows strong resistance to novel insecticides (Jones et al., 2008; McKenzie et al., 2009).
B. tabaci has been recorded as a minor pest of cotton and other tropical or semi-tropical crops within the warmer parts of the world and, until recently has been successfully managed with a range of insecticides.
A few biotypes from certain areas have become major pests, often within large mono-cropping areas where they are regularly exposed to insecticides. In these cases, the biotypes have rapidly evolved resistance to almost all currently available insecticides (Cahill et al., 1996; Mushtaq Ahmad et al., 2002; Luo et al., 2010; Wang et al., 2010). Exposure to sustained insecticide treatments may have promoted other characteristics of these 'pest' biotypes, such as increased fecundity and host adaptability. Populations of the cosmopolitan MEAM1 species [see datasheet on B. tabaci (MEAM1)], the Pakistan K biotype and the Mediterranean species are currently within this group. Other presently uncharacterized biotypes within Africa appear specifically adapted to cassava, causing severe losses to this important subsistence crop (Maruthi et al., 2000).
The feeding of B. tabaci adults and nymphs causes chlorotic spots to appear on the surface of the leaves. Depending on the level of infestation, these spots may coalesce until the whole of the leaf is yellow, apart from the area immediately around the veins. Such leaves are later shed. The honeydew produced by the feeding of the nymphs covers the surface of the leaves and can cause a reduction in photosynthetic potential when colonized by moulds. Honeydew can also disfigure flowers and, in the case of cotton, can cause problems in processing the lint. With heavy infestations, plant height, number of internodes and quality and quantity of yield can be affected (for example, in cotton).
Most biotypes of B. tabaci can vector over 60 plant viruses in the genera Geminivirus, Closterovirus, Nepovirus, Carlavirus, Potyvirus and a rod-shaped DNA virus (Markham et al., 1994; Alegbejo, 2000). Those biotypes that are poor vectors, appear so, due to their inability to feed on alternative host plant species (Bedford et al., 1994b). Whitefly-transmitted geminiviruses, now called begomoviruses, are by far the most important agriculturally, causing yield losses to crops of between 20 and 100% (Brown and Bird, 1992; Cathrin and Ghanim, 2014). Begomoviruses cause a range of different symptoms that include yellow mosaics, yellow veining, leaf curling, stunting and vein thickening. Presently a million ha of cotton is being decimated in Pakistan by cotton leaf curl disease (CLCuV) (Mansoor et al., 1993) and important African subsistence crops such as cassava are affected by begomoviruses such as African cassava mosaic virus (ACMV). Tomato crops throughout the world are particularly susceptible to many different begomoviruses, and in most cases exhibit yellow leaf curl symptoms. This has caused their initial characterization as Tomato yellow leaf curl virus (TYLCV). TYLCV has also recently been recorded in the New World, as well as several other begomoviruses such as Tomato mottle virus (EPPO/CABI, 1996), Tobacco leaf curl virus (TLCV), Sida golden mosaic virus (SiGMV), Squash leaf curl virus (SLCV), Cotton leaf crumple virus (CLCV) and Bean golden mosaic virus (BGMV) some of which cause heavy yield losses in their respective hosts. Dual infections have also been shown to occur (Bedford et al., 1994c).
Europe presently has five known begomoviruses. Three have been shown to no longer be transmissible by B. tabaci: Honeysuckle yellow vein mosaic (also known as Tobacco leaf curl virus), Abutilon mosaic virus (Bedford et al., 1994a) and Ipomea yellow vein virus (Banks et al., 1999), possibly through many years of vegetative propagation of their ornamental host plants. The others are two different transmissible TYLCVs that are causing major crop losses within the tomato industries of Spain, Portugal, Italy and the Canary Islands. Indigenous weed species such as Solanum nigrum and Datura stramonium have also been shown as field reservoirs for these tomato viruses (Bedford et al., 1998) and may be the source of others yet to be identified within Europe. Two B. tabaci-transmitted closteroviruses are also now affecting European crops, including those in the Canary Islands. Cucurbit yellow stunting disorder, is causing severe damage to cucumbers and melons in southern Europe (Celix et al., 1996), along with Tomato chlorosis virus (Navas-Castillo et al., 2000). There are also reports of a third closterovirus, Tomato infectious chlorosis virus, in Europe (Duffus et al., 1996) although this virus currently appears not to be of economic significance. However, a Bemisia-transmitted potyvirus, Cucumber yellow vein virus, appeared in cucumber crops in southern Spain for the first time in 2000 (Cuadrado et al., 2001). Despite a crop destruction programme to eradicate this virus, it has recently spread to melon crops in the region. Protected Zones (e.g. UK and Finland) within Europe remain free from damaging begomoviruses (Cuthbertson and Vänninen, 2015).
In Pakistan, the K biotype is responsible for the spread of a decimating viral disease of cotton, cotton leaf curl disease (CLCuD) (Briddon and Markham, 2000). This disease first became a serious problem in the early 1990s, rapidly affecting a million ha of cotton, which comprises 60% of the country's foreign exchange (Mansoor et al., 1993).
Mediterranean species (Biotype Q)
The Mediterranean species (formerly known as Q biotype) is found throughout the Iberian peninsula, around the Mediterranean basin (including Israel) and in the Canary Islands. It is widely thought that this is the indigenous biotype to these regions, although it co-exists with MEAM1 species in Israel, Italy and the Canary Islands. A population of MEAM 1 was recorded within a Mediterranean species population around Almeria in southern Spain in 1995. It appears that this population failed to become established since recent surveys have only identified Mediterranean species. Mediterranean species was first recorded entering Guatemala in 2009 (Bethke et al., 2009) and the UK in 2012 (Powell et al., 2012). Mediterranean species has, over recent years, been exposed to extensive insecticide applications and within areas of intensive agriculture exhibits a high level of resistance (Dennehy et al., 2010). The use of IPM control programmes is presently restricted where crops are susceptible to viruses. This is particularly the case with Tomato yellow leaf curl viruses which are transmitted very efficiently by B. tabaci. Because of insecticide resistance, large numbers of Mediterranean species often infest crops within southern Europe, resulting in rapid spread of viruses to newly planted crops. Field grown tomato crops in areas of southern Spain and Morocco have recently suffered 100% losses and TYLCV has spread to Phaseolus vulgaris and Capsicum annuum crops.