Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar
Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar
Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar
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Conclusions <strong>and</strong> Recommendations<br />
CHAPTER 3.14<br />
Conclusions <strong>and</strong> Recommendations<br />
Despite over 40 years of research on<br />
Bemisia tabaci (Gennadius)<br />
(Homoptera:Aleyrodidae) as a pest <strong>and</strong><br />
vector of plant <strong>viruses</strong>, this <strong>whitefly</strong><br />
species cont<strong>in</strong>ues to cause<br />
considerable damage to food <strong>and</strong><br />
<strong>in</strong>dustrial crops <strong>in</strong> Mexico, Central<br />
America <strong>and</strong> <strong>the</strong> Caribbean. B. tabaci<br />
first became a pest of cotton<br />
(Gossypium hirsutum L.) <strong>in</strong> Middle<br />
America, <strong>and</strong> <strong>the</strong>n a major vector of<br />
plant <strong>viruses</strong> <strong>in</strong> common bean<br />
(Phaseolus vulgaris L.) <strong>and</strong> tomato<br />
(Lycopersicon esculentum Mill.)<br />
plant<strong>in</strong>gs throughout <strong>the</strong> region. The<br />
expansion of non-traditional crops <strong>in</strong><br />
<strong>the</strong> 1980s, ma<strong>in</strong>ly vegetables for<br />
export, fur<strong>the</strong>r aggravated <strong>the</strong> problem<br />
by provid<strong>in</strong>g more reproductive hosts<br />
for <strong>the</strong> <strong>whitefly</strong> pest <strong>and</strong> a higher<br />
dem<strong>and</strong> for pesticides. The<br />
<strong>in</strong>troduction <strong>in</strong> <strong>the</strong> early 1990s of a<br />
more aggressive <strong>and</strong> polyphagous<br />
biotype (B) of B. tabaci <strong>in</strong> <strong>the</strong> Americas<br />
fur<strong>the</strong>r jeopardized past efforts to<br />
control this pest.<br />
In this region, <strong>whitefly</strong>-<strong>borne</strong><br />
gem<strong>in</strong>i<strong>viruses</strong> (begomo<strong>viruses</strong>) are<br />
more prevalent dur<strong>in</strong>g <strong>the</strong> dry months<br />
of <strong>the</strong> year (November through April),<br />
when B. tabaci populations encounter<br />
more favourable wea<strong>the</strong>r. The area<br />
planted to crops such as melon<br />
* Centro Internacional de Agricultura Tropical<br />
(CIAT), Cali, Colombia.<br />
Francisco Morales*<br />
(Cucumis melo L.), common bean,<br />
tomato, eggplant (Solanum melongena<br />
L.), cucurbits <strong>and</strong> sweet <strong>and</strong> hot<br />
peppers (Capsicum spp. L.) has been<br />
reduced greatly or completely<br />
ab<strong>and</strong>oned dur<strong>in</strong>g this period of <strong>the</strong><br />
year because of <strong>the</strong> frequent outbreaks<br />
of whiteflies <strong>and</strong> <strong>whitefly</strong>-<strong>borne</strong> <strong>viruses</strong>.<br />
The development of B. tabaci from a<br />
harmless <strong>in</strong>sect to a major pest is<br />
closely related to <strong>the</strong> <strong>in</strong>troduction <strong>and</strong><br />
<strong>in</strong>tensive use of pesticides after <strong>the</strong><br />
Second World War. Pesticide abuse<br />
rema<strong>in</strong>s a major factor <strong>in</strong> B. tabaci <strong>and</strong><br />
begomovirus epidemics <strong>in</strong> this region.<br />
Whiteflies are known to develop<br />
resistance to <strong>in</strong>secticides, <strong>the</strong> frequent<br />
use of which elim<strong>in</strong>ates natural<br />
predators of B. tabaci. It is not<br />
uncommon to see farmers spray<strong>in</strong>g<br />
<strong>in</strong>secticides on susceptible crops every<br />
o<strong>the</strong>r day <strong>and</strong> even daily, up until<br />
harvest time, <strong>in</strong> open defiance of food<br />
safety regulations. The high levels of<br />
pesticide residues <strong>in</strong> tomato, pepper,<br />
common bean, eggplant <strong>and</strong> o<strong>the</strong>r<br />
vegetables attacked by B. tabaci<br />
disqualifies <strong>the</strong>se products for sale <strong>in</strong><br />
<strong>in</strong>ternational markets <strong>and</strong> constitutes a<br />
serious health hazard for <strong>the</strong> millions<br />
of rural <strong>and</strong> urban consumers <strong>in</strong> <strong>the</strong><br />
region, where produce is not tested for<br />
toxic residues.<br />
But <strong>the</strong> ma<strong>in</strong> reason for <strong>the</strong><br />
persistence of <strong>the</strong>se pest problems is<br />
<strong>the</strong> lack of qualified technical<br />
assistance for farmers, particularly<br />
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