Cassava whitefly,Bemisia tabaci(Gennadius) (Hemiptera: Aleyrodidae) in East African farming landscapes: a review of the factors determining abundance

Abstract

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a pest species complex that causes widespread damage to cassava, a staple food crop for millions of households in East Africa. Species in the complex cause direct feeding damage to cassava and are the vectors of multiple plant viruses. Whilst significant work has gone into developing virus-resistant cassava cultivars, there has been little research effort aimed at understanding the ecology of these insect vectors. Here we assess critically the knowledge base relating to factors that may lead to high population densities of sub-Saharan African (SSA) B. tabaci species in cassava production landscapes of East Africa. We focus first on empirical studies that have examined biotic or abiotic factors that may lead to high populations. We then identify knowledge gaps that need to be filled to deliver sustainable management solutions. We found that whilst many hypotheses have been put forward to explain the increases in abundance witnessed since the early 1990s, there are little published data and these tend to have been collected in a piecemeal manner. The most critical knowledge gaps identified were: (i) understanding how cassava cultivars and alternative host plants impact population dynamics and natural enemies; (ii) the impact of natural enemies in terms of reducing the frequency of outbreaks and (iii) the use and management of insecticides to delay the development of resistance. In addition, there are several fundamental methodologies that need to be developed and deployed in East Africa to address some of the more challenging knowledge gaps.

Genome-wide analyses of cassava Pathogenesis-related (PR) gene families reveal core transcriptome responses to whitefly infestation, salicylic acid and jasmonic acid

“…In addition, whiteflies (Bemisia tabaci) are major vectors of the viruses Cassava Mosaic Virus and Cassava Brown Streak Virus, which devastate cassava in Eastern and Central Africa [8][9][10][11]. Collectively, these attacks produce significant cassava yield losses [12][13][14]. To reduce the impact of whiteflies on cassava, the identification of new resistance mechanisms and the use of novel transgenic strategies to improve cassava varieties has become increasingly important.…”

Take out the rubbish – Removing NUMTs and pseudogenes from theBemisia tabacicryptic species mtCOI database

“…Although the recently published mtCOI dataset with 513 B. tabaci sequences 8 aimed to address molecular diagnostic needs and species identification with efforts to remove insertion-deletion (indel)-affected sequences from the original dataset 8 , indel-affected sequences nevertheless remained present, while amino acid substitution patterns in sequences unaffected by indels were not examined. With the confusion surrounding the B. tabaci cryptic species nomenclature 1,4,27,28 , the global research community will benefit from this well-curated mtCOI dataset and a standardised workflow to assist with future molecular taxonomy, species diagnostics, and evolutionary genomics studies of the Bemisia whitefly species complex.…”

Review and guide to a future naming system of African Bemisia tabaci species

“…There is a long and detailed history of research on B. tabaci species and the viruses vectored by these species in East Africa. Some fundamental information has been generated about life history, rates of growth under different temperatures, host plant use and natural enemies (Macfadyen et al, ). This type of information is needed to underpin many of the management strategies that are likely to be adopted by smallholder farmers and to provide a foundation for the future development of locally appropriate integrated pest management strategies (Naranjo & Ellsworth, ).…”