Managing a Transboundary Pest: The Fall Armyworm on Maize in Africa

The fall armyworm (Spodoptera frugiperda J.E Smith) (Lepidoptera: Noctuidae) invaded Africa in 2016, and has since spread to all countries in sub-Saharan Africa, causing devastating effects on mainly maize and sorghum. The rapid spread of this pest is aided by its high reproductive rate, high migration ability, wide host range and adaptability to different environments, among others. Since its introduction, many governments purchased and distributed pesticides for emergency control, with minimal regard to their efficacy. In this chapter, we review efforts towards managing this pest, highlight key challenges, and provide our thoughts on considerations for sustainable management of the pest

The Biology of the Red and Green Morphs of the Tobacco Aphid, Myzus Persicae Nicotianae (Blackman) on Flue-Cured Tobacco

The tobacco aphid, Myzus persicae nicotianae is an economically important pest of tobacco. Damage is through direct injury by sucking sap of infested plants as well as reduction of the quality of the leaf by leaving honey-dew which encourages the subsequent growth of sooty-mould. In addition to this, aphids also transmit economically important virus diseases such as the bushy-top virus, the alfalfa mosaic virus and the potato virus-Y. Before 2002, the main colour form of the tobacco aphid in Zimbabwe was green. However, during the 2003/2004 tobacco season, concerns were raised where red forms of the tobacco aphid were observed to be more prevalent than the green form. During the 2004/2005 tobacco season, green forms of the tobacco aphid could only be found with difficulty. In intensive research spanning three years, the days to adulthood, days to 1st nymph, nymphs/day, longevity, fecundity and survival of the red morph were compared to that of the green aphid. Across all years, days to adulthood were the same for the two forms. The red morph produced more nymphs/day than the green morph. Longevity was similar but fecundity was 1½ to 2 times higher for the red morph than the green aphid. The red morph survived longer than the green aphid. These parameters combined to give the red morph of the tobacco aphid a greater reproductive potential and rate of population increase over the green morph thereby partly explaining the sudden increase in this pest in the recent past

The Response of the Red Morph of the Tobacco Aphid, Myzus Persicae Nicotianae, to Insecticides Applied under Laboratory and Field Conditions

The tobacco aphid, Myzus persicae nicotianae is an economically important pest of tobacco, causing extensive yield losses especially as it is an important host of numerous viruses and the sudden shift from the green morph to the red morph is of concern as reports of insecticide resistance are common in this morph. The efficacy of several insecticides was studied, both in the laboratory and in the field, to establish the pest status of the red coloured morph of the tobacco aphid with respect to resistance build up. The laboratory tests confirmed that resistance could be of concern in Monocrotophos only and the field work appeared to show some build up of resistance additionally in Aldicarb. The results point at a need for continued monitoring as well as use of rotations in chemical use in order to reduce the chance of resistance build up

Biting behaviour of Anopheles funestus populations in Mutare and Mutasa districts, Manicaland province, Zimbabwe: Implications for the malaria control programme

Background & objectives: Biting behaviour of Anopheles funestus in Mutare and Mutasa districts, Zimbabwe, is little understood. An investigation was conducted to primarily compare indoor and outdoor biting behaviour of the mosquito, as well as blood meal sources and sporozoite rates. Methods: Monthly adult anopheline sampling was conducted from October 2013 to September 2014 using Centers for Disease Control light-traps, pyrethrum spray catch and artificial pit shelter methods. Mosquitoes sampled by light-traps were divided into two cohorts. In one cohort, traps were left overnight and mosquitoes were collected the following morning, while in the other set, mosquitoes were collected hourly from 1800-0600 hrs . Collected females were identified using morphological characters and categorised according to their abdominal status. Polymerase chain reaction was used to identify An. funestus sibling species and blood meal sources. Infection rate was tested by enzyme-linked immunosorbent assay. Results: Morphological identification showed that indoor and outdoor catches comprised Anopheles funestus (98.3%) and Anopheles gambiae s.l. (1.7%). Of the 2268 mosquitoes collected, 66.2% were caught by light-traps, and 33.8% were caught resting indoors and outdoors. Anopheles funestus and An. gambiae s.l. were trapped more abundantly indoors (68%) than outdoors (32%). Both indoor and outdoor An. funestus densities were higher in wet (4.3) than dry season (1.8). In Burma Valley and Zindi areas, An. funestus demonstrated variable nocturnal indoor and outdoor flight activity rhythms, with two peaks during the night; between 2200-2300 hrs and 0200- 0400 hrs. Human blood index in An. funestus was 0.64, with Plasmodium falciparum infection rate of 1.8%. Interpretation & conclusion: The present work highlighted important information on the host-seeking behaviour, blood meal sources and infection rates in An. funestus. The information would be helpful in improving the vector control strategies

A pilot study to delimit tsetse target populations in Zimbabwe

Tsetse (Glossina sensu stricto) are cyclical vectors of human and animal trypanosomoses, that are presently targeted by the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) coordinated by the African Union. In order to achieve effective control of tsetse, there is need to produce elaborate plans to guide intervention programmes. A model intended to aid in the planning of intervention programmes and assist a fuller understanding of tsetse distribution was applied, in a pilot study in the Masoka area, Mid-Zambezi valley in Zimbabwe, and targeting two savannah species, Glossina morsitans morsitans and Glossina pallidipes. The field study was conducted between March and December 2015 in 105 sites following a standardized grid sampling frame. Presence data were used to study habitat suitability of both species based on climatic and environmental data derived from MODIS and SPOT 5 satellite images. Factors influencing distribution were studied using an Ecological Niche Factor Analysis (ENFA) whilst habitat suitability was predicted using a Maximum Entropy (MaxEnt) model at a spatial resolution of 250 m. Area Under the Curve (AUC), an indicator of model performance, was 0.89 for G. m. morsitans and 0.96 for G. pallidipes. We then used the predicted suitable areas to calculate the probability that flies were really absent from the grid cells where they were not captured during the study based on a probability model using a risk threshold of 0.05. Apart from grid cells where G. m. morsitans and G. pallidipes were captured, there was a high probability of presence in an additional 128 km2 and 144 km2 respectively. The modelling process promised to be useful in optimizing the outputs of presence/absence surveys, allowing the definition of tsetse infested areas with improved accuracy. The methodology proposed here can be extended to all the tsetse infested parts of Zimbabwe and may also be useful for other PATTEC national initiatives in other African countries

Land cover in Masoka area.

<p>Land cover units were discriminated based on a supervised classification of Spot imagery from November 2014.</p

Variable contributions, ROC curves and AUCs of the Maxent models for tsetse distribution.

<p>G. m. morsitans is presented on the top pannel and G. pallidipes at the bottom. nlst, night land surface temperature; avg, average; treecv, tree cover; pd, patch density; dlst, day land surface temperature; dem, digital elevation model.</p

Ecological niche factor analysis (ENFA) of tsetse distribution in the Masoka area.

<p>First plans of the ENFA of <i>G</i>. <i>m</i>. <i>morsitans</i> is presented on the left panel and <i>G</i>. <i>pallidipes</i> on the right one. For each species, the light gray polygon shows the overall environmental conditions available in the study area whilst the dark gray one shows environmental conditions where each species were observed (representation of the realized niche). The small white circle corresponds to the barycenter of each species’ distribution. The first axis (marginality axis) measures the dimension in the ecological space in which the average conditions where the species lives differ from the global conditions with a large marginality value implying that the conditions where the species is found are “far” from the global environmental conditions. The second axis (specialization) measures the narrowness of the niche (ratio of the multidimensional variances of the available to occupied spaces). avg, average; pd, Patch density; NLST, Night Land Surface Temperature; DLST, Day Land Surface Temperature; DEM, Digital Elevation Model; EVI, Enhanced Vegetation Index; MIR, Mid-InfraRed; TWI, topographic wetness index.</p

Apparent densities per trap of tsetse in the Masoka area.

<p>G. m. morsitans is presented in red color on the left and G. pallidipes in blue color on the right.</p