The as per conservative estimate the yield loss in

The country
bean, Lablab purpureus L. (Leguminosae: Papilionaceae), is an important
vegetables grown everywhere in Bangladesh.  Despite of being a
prospective crop, farmers in our country face significant yield loss of beans per
annum due to severe attack of various insect pests. Though no regular
statistical records are kept, as per conservative estimate the yield loss in
country bean due to insect pests is reported to be about 12-30% (Hossain 1990).
Country bean is attacked by nine different insect species and one species of
mite (Alam 1969). In Bangladesh, over 30 different species of arthropods have
been reported in country bean, although only a few occur regularly and cause
economic damage (Alam 1969, Begum 1993, Karim 1993 and 1995, Das 1998,
Islam1999). Among the arthropods, currently the two-spotted
spider mite, Tetranychus urticae Koch
(Acari: Tetranychidae), is considered as one of the important pests of country
beans in Bangladesh.

The two-spotted
spider mite (TSSM) is a polyphagous and destructive pest of agricultural crops
in Bangladesh and throughout the world. Its host range exceeds 1100 plant
species in 140 families of economic value (Pavela 2017). Both nymphs and adults damages
plants by feeding on the leaves, resulting in the collapse of mesophyll cells,
leaf defoliation, browning, production loss, and even plant death (Gorman et
al. 2002; Oliveira and Moreira 2009). The use of chemical pesticides remains a
key policy in integrated pest management system (IPM) due to several
benefits (Endo and Tsurumachi 2001). For the control TSSM and other co-existing
pests, the producer in Bangladesh mostly dependent solely on chemical
pesticides. Owing to its high reproductive capacity, the fast developmental speed,
arrhenotokous parthenogenesis and a very short generation, in combination with
frequent insecticide and acaricide applications, that often leads to the
development of resistance after a few applications (Vassiliou and Kitsis 2013; Uddin et al.
2017).

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