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Simple Summary: Fall armyworm is difficult to control, due to the cryptic feeding of larvae deep inside maize whorls. Even insecticide spray applications do not always effectively reach larvae inside maize whorls. Applying sand/soil directly into whorls of maize plants once an infestation is noticed, is highly relevant in smallholder farming contexts. However, since the efficacy of these methods has not been evaluated before, the need exists to assess their efficacy and to determine application rates. This study was conducted under greenhouse and laboratory conditions on maize plants artificially infested with larvae of different instars. The efficacy of treatments was generally low and varied largely between experiments. Ash treatments resulted in significant mortality of 1st and 5th instars under laboratory conditions. Despite variability in efficacy, these alternative methods have value in IPM systems for smallholder farmers, provided they are applied timeously. Cryptic feeding inside maize whorls makes it difficult to control fall armyworm (FAW). Smallholder farmers use alternative methods of control, of which the efficacy is uncertain. We determined the efficacy of wood ash and soil for the control of FAW and recorded its effect on larval preference and ballooning. Maize plants were artificially infested with larvae of different instars and treatments were either soil, wet ash, or dry ash, applied as single preventative or curative applications. Larvae exhibited non-preference for treated leaves in choice tests. The efficacy of treatments varied largely between experiments. Under laboratory conditions, ash treatments resulted in significant mortality of 1st and 5th instars. Dry and wet ash as curative applications for 1st instars resulted in 67 and 66% mortality, respectively, compared to mortality recorded in the control (22%). Under field conditions, survival of 3rd instars on treated plants was low (21–34%), compared to 70% on untreated plants. Due to the high variability in efficacy, the use of these alternative methods does not guarantee effective control. They do, however, have a place in IPM systems if applied as soon as infestations are observed and when larvae as still small. Recommendations on the use of ash and soil as spot treatments against FAW are provided. [ABSTRACT FROM AUTHOR]

Insecticides and genetically modified Bt crops are the main tools for control of the fall armyworm, Spodoptera frugiperda (J.E. Smith). Since its invasion of Africa, the Far East, and Australia where Bt crops are largely absent, insecticide use has increased and reduced susceptibility to several insecticides used for decades in its native distribution area have been reported. Poor efficacy at field-level is sometimes incorrectly ascribed to pest resistance, while numerous other factors influence efficacy at field-level. In this paper, we review the history of insecticide resistance in S. frugiperda and discuss the influence that life history traits, migration ecology, and chemical control practices may have on control efficacy and resistance evolution. The indirect role that poor national policies have on pesticide use practices, and indirectly on control efficacy and selection pressure is discussed. Evidence shows that local selection for resistance drives resistance evolution. Integrated pest management, rather than reliance on a single tactic, is the best way to suppress S. frugiperda numbers and the over-use of insecticides which selects for resistance. [ABSTRACT FROM AUTHOR]

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is a very destructive polyphagous insect pest of cereal crops accounting for up to 100% yield losses. To survive winter low temperatures in the Americas, adults FAW are known to migrate south for warmer climates and then re‐invade northern USA and Canada the following summer. Since its African invasion, no studies have looked at its overwintering biology. Specifically, there is no information on in situ ontogenetic low temperature tolerance, despite its significance in explaining overwintering survival. Here, we thus investigated low temperature tolerance of FAW larvae (3rd, 4th, 5th and 6th) and adults from field populations through assessing basal stress tolerance (critical thermal minima [CTmin], supercooling point [SCP] and chill coma recovery time [CCRT]) and plasticity using standardized protocols. Our results showed significant life stage effects on low temperature tolerance, although all were chill‐susceptible. Adults had lower CTmin and CCRT than larvae (higher cold tolerance). However, early instar larvae had significantly depressed SCPs than later instars and adults. All larval instars tested showed no plastic responses to CTmin, while for adults, cold hardening appeared to come at a cost of CTmin. These results suggest ontogenetic differences in S. frugiperda cold hardiness albeit all are susceptible to chilling. Second, the absence or cost of hardening confirms FAW's maladaptation to low temperatures. However, Botswana microclimate records show that severe low temperature stress is limited, and thus, in situ overwintering is possible. These results are important in developing informed pest management options for effective management of FAW in Africa. [ABSTRACT FROM AUTHOR]

Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is a major pest of maize. Yield losses between 30 and 70% in the Americas and between 11 and 100% in Africa have been reported. Little information exists on the effect of pest damage during different plant growth stages on yield loss. Previous studies showed that insecticide applications at weekly intervals did not always provide a yield gain comparable to only a single or two well-timed applications. In this study, we completed four field trials under high natural pest pressure. Treatments consisted of different regimes of insecticide applications that provided protection against damage during different growth stages. In one trial, the mean incidence of infested plants was 65%, and the yield benefit gained from four insecticide applications was 32.6%. The other three trials had 16 treatments which were divided into two spray sequences to protect plants against FAW damage for different lengths of time, between early vegetative stages and tasseling. Yield losses were 41.9, 26.5 and 56.8% for the three respective trials if no insecticides were applied. Yield loss of plants protected during earlier growth stages was significantly lower than that of the treatments which provided protection during later growth stages. More than three spray applications generally completed did not provide further yield gains. Plants that were protected more during early growth stages yield higher than plants protected during later growths stages. [ABSTRACT FROM AUTHOR]

The fall armyworm (Spodoptera frugiperda) is a pest of tropical origin which recently invaded Africa, the Far East and Australia. Temperature, therefore, plays an important role in its invasion biology, since this pest does not go into diapause. The aim of this study was to determine the development rate of S. frugiperda at different temperatures and to calculate the number of degree-days (°D) required for each stage to complete its development. This study was conducted at five different temperatures—18, 22, 26, 30 and 32 ± 1 °C. Larvae were reared individually in Petri dishes with sweetcorn kernels provided as food. The development rate of S. frugiperda increased linearly with increasing temperatures between 18 and 30 °C and larval survival was the highest between 26 and 30 °C. The optimal range for egg, larval and egg-to-adult development was between 26 and 30 °C. The optimum temperature with the fastest larval development rate and lowest mortality was at 30 °C. The pupal development period ranged between 7.82 and 30.68 days (32–18 °C). The minimum temperature threshold for egg and larva development was 13.01 and 12.12 °C, respectively, 13.06 °C for pupae and 12.57 °C for egg-to-adult development. Degree-day requirements for the development of the respective life cycle stages of S. frugiperda were 35.68 ± 0.22 for eggs, 204.60 ± 1.23 °D for larvae, 150.54 ± 0.93 °D for pupae and 391.61 ± 1.42 °D for egg-to-adult development. [ABSTRACT FROM AUTHOR]

Busseola fusca (Fuller; Lepidoptera: Noctuidae) is an important pest of maize in Africa and can be effectively controlled by Bt maize. However, the sustainability of this technology is threatened by resistance evolution, which necessitates the implementation of the high-dose/refuge insect resistance management (IRM) strategy. Despite the success of this IRM strategy, it is based on several assumptions about insect-hostplant interactions that are not always valid for different pest species. In this study, the plant abandonment behavior of Cry1Ab-resistant and susceptible B. fusca larvae were evaluated on a non-Bt, single toxin (Cry1Ab), and a pyramid event (Cry1.105 + Cry2Ab2) of maize over a four-day period. The aim was to determine if larvae are more likely to abandon maize plants that contain Bt-toxins than conventional non-Bt plants, and if resistance to the Cry1Ab-toxin affects this behavior. This study found that both Bt-resistant and susceptible B. fusca neonate larvae show feeding avoidance behavior and increased plant abandonment rates when exposed to Bt maize leaf tissue. The implications of these findings for the design of IRM strategies and choice of refuge structures are discussed in the context of Bt maize in Africa. [ABSTRACT FROM AUTHOR]

Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a destructive pest of maize throughout the African continent. Bt maize is an effective control measure for this pest, however, selection pressure for resistance evolution is high. This necessitates the implementation of insect resistance management (IRM) strategies such as the high-dose/refuge strategy. This IRM strategy relies on the validity of several assumptions about the behaviour of pests during insect-hostplant interactions. In this study, the migration behaviour of B. fusca larvae was evaluated in a semi-field (greenhouse) and field setting. The effect of factors such as different Cry proteins, plant growth stage at infestation, and plant density on the rate and distance of larval migration were investigated over four and five week periods. Migration of the larvae were recorded by using both a leaf feeding damage rating scale and destructive sampling at the end of the trials. Results indicated that B. fusca larval migration success was significantly affected by plant growth stage and plant density—while limited larval migration was recorded in plots inoculated with larvae at a late growth stage (V10), higher plant density facilitated increased interplant migration. The results also suggest that B. fusca larvae do not migrate extensively (rarely further than two plants from the natal plant) and that larval mortality is high. Implications for IRM strategies are discussed. [ABSTRACT FROM AUTHOR]