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Variance associated with genotype, cause of death, and stage of growth on mortality of immature stages of B. tabaci SSA1 on cassava in Uganda.
Source publication
Natural death is a key determinant of a species population dynamics. Thus, a clear understanding of natural mortality factors aids the development of appropriate management strategies for insect pests. Cohort-based life tables were constructed to determine the sources and rates of mortality of field populations of the pest, Bemisia tabaci Sub-Sahar...
Contexts in source publication
Context 1
... information was then used to estimate the probability of death from all causes (aq x : Table S2) at a given stage of growth according to Carey, 1989. The aq x values were then used to compute the survival (al x : Table S3) of the immature B. tabaci populations subjected to all causes of death in a given stage to construct the multiple decrement life table following the methods of Carey (1989). ...Context 2
... the ANOVA result, the variation in MMR, Ic and k-value was due to cause of death nested within genotype (Table 3). There was considerable variation in MMRs for each cause of death when pooled over all immature stages; the highest median rates of death were associated with disappearance in both genotypes in all cohorts; median MMR was 0.355 in Alado alado (Fig. 1A). ...Context 3
... highest stage-specifi c mortality for both genotypes was observed in the third instar stage; 55% for Alado alado and 49% for NAROCASS 1. Only about 12% of the nymphs survived to adult emergence in both genotypes (Table S3). For both the egg and nymph stages, disappearance was associated with the highest mortality of 73% and 69% of nymph deaths in Alado alado and NAROCASS 1, respectively (Table S3). ...Similar publications
Anagyrus lopezi (De Santis) is an endo-specific parasitoid of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. The objective of the study was to determine the efficiency and effectiveness of parasitoids by estimating the parameters of functional response. A fertile female of A. lopezi was tested on the 2nd and 3rd instar nymphs of P. mani...
Citations
... However, there is still a diversity of cassava cultivars (both traditional varieties and ICVs) grown by farmers in East Africa because not all cassava traits have been the focus of breeding efforts (e.g., complex traits like cooking time, taste and texture of roots are very cultivar-specific). Furthermore, some traditional varieties have high levels of natural tolerance to certain pest species and diseases, but not all pests and diseases (Katono et al., 2021a;2021b). Some varieties released to help control CMD and CBSD pandemics may also be suitable hosts for whitefly pests Omongo et al., 2022). ...
A key constraint to cassava productivity in Africa is the lack of adoption of improved cassava varieties tolerant to pests and diseases. To understand the drivers of adoption behavior, we examine the simultaneous adoption of improved cassava varieties and intercropping by 1200 smallholder farmers in Malawi, Tanzania, and Uganda. Using a linear model, we find that varietal characteristics, such as yield and early maturity, are critical drivers of adoption. Access to extension and credit is associated with an increase in the attractiveness of yield‐improving characteristics. We conclude that a more targeted extension approach would increase technology adoption in these countries.
... In general, B. tabaci populations are favored by elevated temperatures and moderate rainfall (Sseruwagi et al., 2004). Similarly, high rainfall amounts can also cause high mortality of whiteflies and other insect and mite pestslargely through a washing-away effect (Leite et al., 2005;Katono et al., 2021;Amjad-Bashir et al., 2022;Zsögön et al., 2022) which in turn reduces pest and natural enemy. We observed a strong positive relationship between B. tabaci nymph abundance and parasitism rate by E. lutea in all the AEZs, similar to the findings of Kalyebi et al. (2021) in Burkina Faso, Benin, and Togo, which all together support the assumption that the action of parasitoids on B. tabaci is density-dependent (Otim et al., 2006(Otim et al., , 2018. ...
... Other studies have shown that altitude influences the abundance of B. tabaci; however, the mechanisms explaining these effects have not been elucidated. It has been noted that, at higher altitudes (>1000 m above sea level), there are fewer plant disease problems and an absence of B. tabaci in cassava (Jeremiah et al., 2015;Doungous et al., 2022), probably due to low whitefly reproductive success and high mortality at lower temperatures at higher altitudes (Katono et al., 2021;Amjad-Bashir et al., 2022;Zsögön et al., 2022). ...
... Dislodgement from the plant surface is a common cause of mortality in the sessile immature stages of B. argentifolii and recent studies on cassava identified disappearance to be the key factor. 61 Naranjo and Ellsworth 27 showed that death of all immature stages by dislodgement on cotton is associated with wind and blowing dust generated by monsoon storms in our region, whereas rainfall can contribute to dislodgement of eggs and first-instar nymphs. Predation from beetles and lacewings was associated with removal of larger nymphs from the plant surface. ...
BACKGROUND
The population dynamics of polyphagous pests such as Bemisia argentifolii (B. tabaci MEAM1) are governed by complex, interacting factors involving its cultivated and wild host plants, seasonality, movement and demography. To understand mechanisms contributing to population development and pest success within the agroecosystem, contiguous multi‐host field sites were established in three environmentally distinct areas in Arizona. Life tables quantified and partition models described mortality sources and rates for immature insect stages on each host plant.
RESULTS
Predation and dislodgement were the largest sources of marginal mortality, supplied the highest irreplaceable mortality and predation was the key factor. Rates of mortality were best predicted, in order, by source, temperature, host plant and season. Marginal mortality was highest for fourth‐stage nymphs followed by eggs. Mortality rates were predicted in descending order by stage, temperature and season. Survivorship patterns varied among host plants, and generational mortality averaged 70% on spring cantaloupes but nearly 95% on all other hosts. Population density varied seasonally, persisting at low levels on winter hosts and expanding beginning in the spring; perennial hosts and weeds bridge populations year‐round.
CONCLUSION
Survival on winter hosts such as broccoli, albeit low, enables population continuity, whereas unusually high survivorship on spring crops like cantaloupe is an ecological release propelling population growth and driving regional dynamics in the summer and fall. This detailed understanding of mortality dynamics provides clues to the success of this invasive pest in our agroecosystems and facilitates opportunities for improved pest management at a broader landscape scale. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
... Although many species of whiteflies are reported on cassava (Belloti and Van Schoonhoven, 1978;Legg, 1995;Kamau et al., 2005;Mugerwa et al., 2012;Guastella et al., 2015), few are predominant and cause substantial damage to the crop. In the Neotropics, Aleurotrachelus socialis (Bondar) and Aleurothrixus aepim (Goeldi) are the most devastating (Belloti and Van Schoonhoven, 1978), while in Africa it is the African cassava whitefly species, Bemisia tabaci Sub-Saharan Africa 1 (SSA1) and Sub-Saharan Africa 2 (SSA2) (Mugerwa et al., 2012;Ally et al., 2019;Katono et al., 2021a). ...
Cassava whitefly are a group of cryptic species within the Bemisia tabaci sensu lato complex that causes significant damage to cassava in Africa. B. tabaci Sub-Saharan Africa 1 (SSA1) is the major species in the study region which transmits plant-virus diseases to cassava and causes direct feeding damage. Benefits from management of cassava viral diseases through deployment of resistant varieties are being undermined by their susceptibility to B. tabaci SSA1 and the problem is exacerbated by high populations of B. tabaci in cassava fields. To develop a clean seed system that is disease-free, the judicious use of insecticides is required to manage this pest and vector. This study evaluated the effect of timing of insecticide application on controlling B. tabaci SSA1 population abundance and damage to cassava. Field trials were carried out between 2017 and 2018 in Kamuli and Wakiso districts of Uganda using the widely available insecticide Imidacloprid. Three cassava cultivars (NAROCASS1, SAUTI, KBH/2002/026) were planted in a randomized complete block trial design replicated three times. The insecticide was applied in split-plots designated as: (i) no protection (NP), no insecticide applied (control), (ii) early protection (EP), insecticide applied 2 times between 0 and 4 months after planting, (iii) long protection (LP), insecticide applied 3 times between 0 and 8 months after planting, and (iv) total protection (TP), insecticide applied 4 times between 0 and 12 months after planting. Except for control plots, stem cuttings were first dipped into a diluted solution of Imidacloprid prior to planting. Bi-monthly data were collected on the B. tabaci population, feeding damage, cassava mosaic disease and cassava brown streak disease. Stem cuttings and root yields were determined at harvest. The marginal rate of return for each treatment was calculated to determine cost effectiveness. Insecticide application effectively reduced B. tabaci populations, feeding damage and disease spread. Cassava yield differed significantly with insecticide treatment and amongst cultivars. Root and stem yield losses of >60% was recorded in unprotected control plots. The marginal rate of return of the early protection (0–4 MAP) program was 163%. We discuss these findings and the implication for judicious use of insecticides as part of a cassava clean seed system.
