Abstract
Invasive alien species have environmental, economic and social impacts, disproportionally threatening livelihood and food security of smallholder farmers in low- and medium-income countries. Fall armyworm (FAW) (Spodoptera frugiperda), an invasive insect pest from the Americas, causes considerable losses on maize to smallholder farmers in Africa since 2016. The increased use of pesticides to control FAW in Africa raises concerns for health and environmental risks resulting in a growing interest in research on biological control options for smallholder farmers. In order to evaluate the occurrence of local natural enemies attacking FAW, we collected on a weekly basis FAW eggs and larvae during a maize crop cycle in the rainy season of 2018–2019 at four locations in the Lusaka and Central provinces in Zambia. A total of 4373 larvae and 162 egg masses were collected. For each location and date of collection, crop stage, the number of plants checked and amount of damage were recorded to analyse which factors best explain the occurrence of the natural enemy species on maize. Overall parasitism rates from local natural enemies at each location varied between 8.45% and 33.11%. We identified 12 different egg-larval, larval and larval-pupal parasitoid species. Location, maize growth stage, pest density and larval stage significantly affected parasitoid species occurrence. Our findings indicate that there is potential for increasing local populations of natural enemies of FAW through conservation biological control programmes and develop safe and practical control methods for smallholder farmers.
Highlights
Invasive alien species (IAS) have environmental, economic and social impacts, disproportionally threatening livelihood and food security of smallholder farmers in lowand medium-income countries (LMIC) (Early et al 2016; Paini et al 2016; Pratt et al 2017)
One additional parasitoid species recovered from one Fall armyworm (FAW) pupa which was absent during the rainy season has been identified as Metopius discolour Tosquinet
Sub-samples of the hymenopteran parasitoid larvae that died in the Petri dishes were sent for molecular identification, which revealed that they belonged to the species Chelonus bifoveolatus Szépligeti and Coccygidium luteum Brullé, and further, morphological examinations suggest that both species were abundant
Summary
Invasive alien species (IAS) have environmental, economic and social impacts, disproportionally threatening livelihood and food security of smallholder farmers in lowand medium-income countries (LMIC) (Early et al 2016; Paini et al 2016; Pratt et al 2017). Smallholder farmers in LMIC face important crop losses due to a lack of knowledge about management practices at early stages of the invasion (Machekano et al 2017). Classical biological control through the introduction of exotic natural enemies has managed to save important staple and cash crops from IAS where chemicals have failed including the citrus industry and cassava production (Menzler-Hokkanen 2006). Investigations on classical biocontrol agents can be long-lasting and, when no suitable agent is available or when time is running out to save crops, augmentative and conservation biological control can play an important role in mitigating damage caused by established IAS. Augmentative and conservation biological control strategies use local natural enemies to target a pest, their implementation differs regarding the type of biological control agents and techniques used (Lazarovits et al 2007)
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