Is High Whitefly Abundance on Cassava in Sub-Saharan Africa Driven by Biological Traits of a Specific, Cryptic Bemisia tabaci Species?

Abstract

In East Africa, the prevalent Bemisia tabaci whiteflies on the food security crop cassava are classified as sub-Saharan Africa (SSA) species. Economically damaging cassava whitefly populations were associated with the SSA2 species in the 1990s, but more recently, it has been to SSA1 species. To investigate whether biological traits (number of first instar nymphs, emerged adults, proportion of females in progeny and development time) of the cassava whitefly species are significant drivers of the observed field abundance, our study determined the development of SSA1 sub-group (SG) 1 (5 populations), SG2 (5 populations), SG3 (1 population) and SSA2 (1 population) on cassava and eggplant under laboratory conditions. SSA1-(SG1-SG2) and SSA2 populations’ development traits were similar. Regardless of the host plant, SSA1-SG2 populations had the highest number of first instar nymphs (60.6 ± 3.4) and emerged adults (50.9 ± 3.6), followed by SSA1-SG1 (55.5 ± 3.2 and 44.6 ± 3.3), SSA2 (45.8 ± 5.7 and 32.6 ± 5.1) and the lowest were SSA1-SG3 (34.2 ± 6.1 and 32.0 ± 7.1) populations. SSA1-SG3 population had the shortest egg–adult emergence development time (26.7 days), followed by SSA1-SG1 (29.1 days), SSA1-SG2 (29.6 days) and SSA2 (32.2 days). Regardless of the whitefly population, development time was significantly shorter on eggplant (25.1 ± 0.9 days) than cassava (34.6 ± 1.0 days). These results support that SSA1-(SG1-SG2) and SSA2 B. tabaci can become highly abundant on cassava, with their species classification alone not correlating with observed abundance and prevalence.

Distribution and Molecular Diversity of Whitefly Species Colonizing Cassava in Kenya

“…It is known to have over 1000 host-plant species including cassava, sweet potato, tomato, cucurbits, cotton as well as various fruits and ornamental plants [ 15 , 16 ]. Bemisia tabaci is known to transmit over 300 economically important plant viruses including begomoviruses, criniviruses , carlaviruses , torradoviruses and ipomoviruses [ 4 , 17 , 18 , 19 , 20 ].…”

The role of pathogen‐mediated insect superabundance in the East African emergence of a plant virus

“…SSA2 is one of five B. tabaci species found colonising cassava in sub‐Saharan Africa (SSA1 to SSA5; Ally et al, 2019). Although high B. tabaci abundance has persisted on cassava regionally (Ally et al, 2019), SSA2 has rarely been found in significant numbers in the region subsequent to the initial report by Legg et al (2002) (Ally et al, 2019; Legg et al, 2014; Mugerwa, Colvin, et al, 2021; Mugerwa, Sseruwagi, et al, 2021). As such, published experimental evidence since the initial expansion has tended not to support INViS.…”

“…As such, published experimental evidence since the initial expansion has tended not to support INViS. Recent reports, however, of SSA2 on cassava in the drier and hotter regions of northern Uganda (Mugerwa, Colvin, et al, 2021; Mugerwa, Sseruwagi, et al, 2021) and nearby south Sudan (Misaka et al, 2020), has rendered it feasible that B. tabaci SSA2 moved southwards with the initial CMD expansion—but did not ultimately displace B. tabaci SSA1 species due to a lack of adaptation to the environment of central Uganda.…”

Cassava mosaic disease and its whitefly vector in Cameroon: Incidence, severity and whitefly numbers from field surveys

“…Our data highlighted counts of more than 50 adult whiteflies per plant in some surveyed fields. This is alarming since epidemics of CMD and other cassava diseases in Uganda, parts of western Kenya and north-western Tanzania have been associated with similar whitefly populations on cassava ( Colvin et al, 2004 ; Legg et al, 2014b ; Mugerwa et al, 2021 ).…”