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This experiment was conducted at the Teaching and Research Farm of the Faculty of Agriculture and Veterinary Medicine, Imo State University, Owerri, between May and August 2019. The experiment investigated the effect of garlic (Allium sativum) extracts in the control of maize stem borer (Busseola fusca) in Owerri. The experiment was arranged in a Randomized Complete Block Design (RCBD) with four treatments and three replications. In this trial, various levels of treatments were used. (0ml, 50ml, 100ml, 150ml) and (0g, 50g, 100g, 150g) for crude liquid and crude powder extracts. Proximate analysis was carried out on Allium sativum which revealed the nutritional contents in percentages such as moisture content (62.86), Ash Content (0.90). Phytochemical analysis was carried out which revealed the presence of anti-nutritional constituents in percentages, such as Tannin (0.97), Phenol (0.15), Alkaloid (4.77), flavonoid (1.96), Saponin (1.44), oxalate (3.38), HCN (0.01) and Phytate (0.19). More so, infrared spectroscopy of Allium sativum revealed the presence of bioactive compounds and the different wavelength at which they were absorbed. Such compounds are amines (1032.36 and 3998.00), alkane and alkyl (2935.00), Alkene (1641.00), Aromatic compounds (1406.39), Alcohol (1126.14), Alkyl halides (532.36 and 593.00). data were collected on number of insects, number of plants infested leaf area, leaf area index, plant height, number of leaves, number of fruits per plot, stem girth and fruit yield and subjected to analysis of variance at 0.05% level of significance. The results of the trial revealed that the plots that received 50mls, 100mls and 150mls of crude liquid extracts suppressed number of insects (1.0, 1.3 and 1.0) also, plots that received 50mls, 100mls of crude liquid extract at 1WAT reduced the number of plants infested (0.3 and 0.3) than the crude powder extract (0.6 and 1.0) and these were significantly different (P= 0.05). The lowest mean (51.38kg/ha) and (2.67) in fruit yield and number of fruit per plot were recorded from untreated plots. The plant height showed no significant difference (P≤ 0.05). In this study, Allium sativum reduced the number of insect pests attack (Busseola fusca) on maize plant. This action might be due to the anti-nutritional or bioactive compounds inherent in Allium sativum. [ABSTRACT FROM AUTHOR]

In insect communities, the outcome of intra- and inter-specific competitions for food utilisation depend primarily upon density and duration even inter-specific competitions can occur when they are not sharing the same feeding niche such as between foliar feeders and stemborers. Experimental manipulations of larval densities and the durations of common diet feeding of fall armyworm (FAW), S. frugiperda, and the African lepidopteran stemborers, Busseola fusca, Sesamia calamistis and Chilo partellus, were conducted to determine how the density and the duration of resource utilization affected larval survival and the relative growth rate (RGR) in intra- and inter-specific interactions. The results showed both intra- and interspecific competitions were observed among all the four species and interspecific competition was significantly stronger between the stemborers than between the FAW and the stemborers. The results showed that multiple infestations of cereal plants with low larval densities of each species at optimum conditions will very likely prolong the coexistence between FAW and stemborers. In addition, the time partitioning of the resource use significantly influenced this coexistence. [ABSTRACT FROM AUTHOR]

African stem borer, Busseola fusca Fuller (Noctuidae) and spotted stem borer, Chilo partellus Swinhoe (Crambidae) cause more than 40 % of grain yield loss in cereals and bothpests co-exist in mid-altitudes in Kenya. Development of sorghum with dual resistance to B. fusca and C. partellus has been difficult due to the inadequate understanding of inheritance of resistance traits to the two species. The objective of this study was to investigate the genetics of dual resistance to the two insect species in sorghum. Thirty sorghum populations derived from crossing sorghum lines with varying levels of resistance to the two insect species were studied. The experiments were conducted in two separate sites at Embu and Kiboko in Kenya with two replications per site. North Calorina Design II mating design was used. Artificial infestation with first instar neonates of each pest species was done at 30 days after planting in both sites. Data collected included sorghum damage due to the two borer species and agro-morphological traits. Genetic analyses were performed using line x tester method using Genstat statistical software. Data analyses revealed that general combining ability (GCA) and specific combining ability (SCA) effects were significant for foliar and stem damage traits, indicating that additive and non-additive gene effects conditioned resistance to B. fusca and C. partellus. Sorghum lines ICSA 464, ICSB 474, ICSB 464 and ICSA 472 and ICSB 473 exhibited desirable high negative GCA effects to B. fusca and C. partellus. These parents could be used in development of sorghum with dual resistance to B. fusca and C. partellus thus contributing to sustainable integrated management of these two stem borer species in sorghum via host plant resistance management. [ABSTRACT FROM AUTHOR]

Exotic invasive insect herbivores have the potential to interfere with existing herbivore-natural enemy interactions in new environments. Fall armyworm (FAW), Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a new invasive pest in maize fields in Africa. Understanding the acceptability and suitability of FAW to existing maize stemborer-parasitoid interactions is the first step in elucidating the impact that this exotic insect pest can have on the existing natural enemies used in biological control of maize stemborers in Kenya. The most commonly used larval parasitoids for biological control programs against maize stemborer communities in East Africa are Cotesia flavipes Cameron (Hymenoptera: Braconidae) and two populations of the native Cotesia sesamiae (Cs-Inland and Cs-Coast) Cameron (Hymenoptera: Braconidae). All these parasitoid species attacked FAW larvae but none yielded offspring, although they induced high non-reproductive host mortality when compared to natural mortality. Furthermore, the parasitoids that inserted their ovipositor into FAW larvae exhibited no significant preference between FAW larvae and their respective stemborer hosts under dual-choice bioassays. In olfactometer bioassays, the parasitoids were more attracted to plants infested by FAW than uninfested plants and even showed a marked preference for the odours of plants infested by FAW over those of plants infested by their natural host counterparts. This study illustrates that exotic pests, such as FAW, can impact existing stemborer-parasitoid interactions associated with maize, even if they cannot be used as hosts by parasitoids associated with these stemborers. Although additional studies are needed, FAW might therefore have a negative impact on stemborer biological control existing before its invasion. [ABSTRACT FROM AUTHOR]

Bt maize is genetically engineered to express insecticidal proteins from the bacterium Bacillus thuringiensis. Bt maize is used extensively by South African farmers to reduce yield losses caused by lepidopteran larvae. Starting in the 2004/2005 season, severe Busseola fusca-associated damage to Cry1Ab-expressing Bt maize was noted by South African farmers. The unsatisfactory pest control was eventually attributed to the development of insect resistance to the Cry1Ab protein in the Bt maize hybrids. An assessment of the historical events surrounding the development of resistance by B. fusca showed that there was room for improvement both in the insect resistance management (IRM) strategy selected and the implementation of the strategy. With the recent arrival of fall armyworm (Spodoptera frugiperda) in Africa, it is important to have IRM programs that are appropriate for all of the pests that constitute the maize lepidopteran pest complex. After the identification of shortcomings in the IRM programs implemented in South Africa, a framework is proposed for effective Bt maize IRM programs. The IRM framework integrates pre-marketing research, post-marketing monitoring, and two-level remedial action plans (RAPs). The core of the framework is a regulator-approved IRM strategy that is based on comprehensive pre-marketing research and serves to guide stakeholders during the post-marketing phase. The framework will assist technology developers and regulators, especially those with nascent regulatory systems, to select and implement IRM strategies that facilitate sustainable pest management.

In Lepidoptera, larval dietary experience of volatile cues can induce adult preference for these cues. However, such induction may require several generations, depending in part on the degree of specialization of the insects. In a previous study, using species of noctuid stem borers with different diet breadths, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and monophagous Busseola nairobica, it was shown that in S. nonagrioides, one generation was enough to induce a preference for vanillin in the resulting gravid females, whereas even two generations failed to induce a response in adults of Busseola spp. In this study, we checked whether a higher number of generations of exposure to a vanillin-enriched medium could induce a significant olfactory preference for this medium in the species B. fusca and B. nairobica, which have narrower host-plant utilization ranges than S. nonagrioides. Larvae were reared to the adult stage on an artificial diet enriched with vanillin for periods of from 2 to 7 or 8 generations, followed by two-choice tests on gravid females using a Y-tube olfactometer. The results showed different responses according to the species: for the oligophagous B. fusca, there was no significant effect of the conditioning, while a significant preference for the odours emitted by this new vanillin-enriched diet was recorded for the polyphagous S. nonagrioides and monophagous B. nairobica, but after different numbers of generations. In conclusion, different diet breadths seem to be associated with different levels of plasticity in the odour preference of adults. The implication of this result for insects' adaptability in a changing landscape is discussed.

Different traits in insects such as locomotor activity, egg-hatching, emergence from puparia and oviposition follow light and dark rhythms. In noctuid stemborer moths, activity cycles of the adults linked to their reproductive traits concentrate at the first half of the night and some of them are highly species specific. However, little information is available on the light and dark rhythm of egg hatching in noctuid stemborer moths as compared to adult's activities (emergence, oviposition and mating). The purpose of this study was to compare the light and dark rhythms of pupal eclosion and egg hatching, respectively, for four main species of Afro-tropical noctuid stemborers under 24 h light-dark cycle conditions. In contrast to pupal eclosion, egg-hatching showed to be less controlled by light and dark rhythms. This arrhythmic pattern on egg-hatching compared to pupal eclosion is discussed in terms of interspecific resource utilization within a community of lepidopteran stemborers sharing the same resource. [ABSTRACT FROM AUTHOR]

Larval dispersal either through ballooning or crawling results in a redistribution of the insect population and infestations within and between plants. In addition, invasive species, such as the fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), and the exotic stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), may displace indigenous stemborers on maize in Africa. To test whether larval dispersal activity may play a role in the displacement of indigenous stemborers, larval dispersal was compared between FAW, C. partellus, and the indigenous species Busseola fusca (Fuller) and Sesamia calamistis (Hampson) (both Lepidoptera: Noctuidae). Twenty potted maize plants were infested with one batch of eggs either from stemborers (B. fusca, S. calamistis, or C. partellus) or from FAW and monitored in the greenhouse for ballooning activities. After egg hatching, both ballooning and non‐ballooning larvae were identified according to species and counted. FAW neonate larvae had greater potential for ballooning off than stemborers, irrespective of species. For each species, more females dispersed than males, and their survival rate was higher than that of non‐ballooning larvae. In addition, plant‐to‐plant larval movements were studied using 6.25‐m2 plots of caged maize in a completely randomized design with five replicates. FAW was found to have wider dispersal and plant damage potential than any of the stemborer species. In conclusion, in contrast to C. partellus, the invasive characteristic of FAW can be explained, in part, by its higher larval dispersal activity compared to stemborers. This difference in larval dispersal might also be considered in sampling plans for monitoring pest density in the field. [ABSTRACT FROM AUTHOR]

• The proportion of maize in the landscape overrides management effects on maize stemborer. • At field level, stemborer infestation was positively associated with plant density. • At high infestation levels, infestation was positively associated with planting date. • At high infestation levels, infestation was negatively associated with the botanic diversity of hedges. • Maize grain yield was weakly negatively associated with stemborer infestation level. Lepidopteran stemborers are a serious pest of maize in Africa. While farmers have adopted cultural control practices at the field scale, it is not clear how these practices affect stemborer infestation levels and how their efficacy is influenced by landscape context. The aim of this 3-year study was to assess the effect of field and landscape factors on maize stemborer infestation levels and maize productivity. Maize infestation levels, yield and biomass production were assessed in 33 farmer fields managed according to local practices. When considering field level factors only, plant density was positively related to stemborer infestation level. During high infestation events, length of tunnelling was positively associated with planting date and negatively with the botanical diversity of hedges. However, the proportion of maize crop in the surrounding landscape was strongly and positively associated with length of tunnelling at 100, 500, 1000 and 1500 m radius, and overrode field level management factors when considered together. Maize grain yield was positively associated with plant density and soil phosphorus content, and not negatively associated with the length of tunnelling. Our findings highlight the need to consider a landscape approach for stemborer pest management, but also indicate that maize is tolerant to low and medium infestation levels of stemborers. [ABSTRACT FROM AUTHOR]

The article focuses on spatio-temporal dynamics of multi-species pest communities and the interactions between them influence the structure of pest complex that attack crops. Topics discussed include lepidopteran stemborer species made up of Busseola fusca (Fuller) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae), and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), and community ecology.

The interactions among insect communities influence the composition of pest complexes that attack crops and, in parallel, their natural enemies, which regulate their abundance. The lepidopteran stemborers have been the major maize pests in Kenya. Their population has been regulated by natural enemies, mostly parasitoids, some of which have been used for biological control. It is not known how a new exotic invasive species, such as the fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera, Noctuidae), may affect the abundance and parasitism of the resident stemborers. For this reason, pest and parasitism surveys have been conducted, before and after the FAW invaded Kenya, in maize fields in 40 localities across 6 agroecological zones (AEZs) during the maize-growing season, as well as at 3 different plant growth stages (pre-tasseling, reproductive, and senescence stages) in 2 elevations at mid-altitude, where all maize stemborer species used to occur together. Results indicated that the introduction of the FAW significantly correlated with the reduction of the abundance of the resident communities of maize stemborers and parasitoids in maize fields; moreover, the decrease of stemborer density after the arrival of FAW occurred mostly at both reproductive and senescent maize stages. It also suggests a possible displacement of stemborers by FAW elsewhere; for example, to other cereals. However, since this study was conducted only three years after the introduction of the FAW, further studies will need to be conducted to confirm such displacements.

Busseola fusca is a maize and sorghum pest that can cause significant damage to both crops. Given that maize is one of the main cereals grown in the worldwide, this pest is a major challenge for maize production and therefore for the economies of several countries. In this paper, based on the life cycle of B. fusca, we propose a mathematical model to study the population dynamics of this insect pest. A sensitivity analysis using the eFast method was performed to show the most important parameters of the model. We present the theoretical analysis of the model. More precisely, we derive a threshold parameter N0, called basic offspring number and show that the trivial equilibrium is globally asymptotically stable whenever N0≤1, while if N0>1, the non trivial equilibrium is globally asymptotically stable. The theoretical results are supported by numerical simulations. [ABSTRACT FROM AUTHOR]

Competitive or facilitative interactions characterise phytophagous insect communities that utilise the same resources. These interactions are often mediated by the host plant. Plant mediation influences the oviposition choices that a community of insects, sharing the same host plant make. In this context, the oviposition choices of females within a community of lepidopteran cereal stemborers namely Busseola fusca, Sesamia calamistis and Chilo partellus were studied in plant choice-experiments under laboratory and field conditions. Gravid females of each species were presented with a choice between maize plants infested by conspecific or heterospecific larvae and uninfested maize plants. The number of eggs and egg batches laid on plants were used to quantify oviposition. Results showed that none of the three stemborer species avoided oviposition on infested maize plants. In some cases a significant preference for infested maize plants were observed. Similarly, data from field trials under natural stemborer infestation, with B. fusca as the only species, showed that the wild ovipositing moths were not avoiding infested plants. Host plant mediation may influence the incidence of multi-species infestations by stemborer species often found in the field. The potential roles of herbivore-induced and egg-deposited-induced plant volatiles in this mechanism are discussed. [ABSTRACT FROM AUTHOR]

Lepidopteran stem borers are among the most important pests of maize in East Africa. Understanding the factors that influence maize stem borers' distribution is crucial in predicting their response to future climate change. The hypothesis of this study was that the potential distribution of the maize stem borers Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) and Busseola fusca (Fuller) (Lepidoptera: Noctuidae) at small scale along altitudinal gradients at Mount Kilimanjaro and Taita Hills in Tanzania andKenya, respectively, depends on other climatic and edaphic factors besides temperature. The species distribution was studied using the maximum entropy (Maxent) application with three climatic (temperature, rainfall and relative humidity) and five soil variables [soil silicon (Si), potassium (K), phosphorus (P), nitrogen (N) concentrations and water-holding capacity (WHc)]. The model accuracy was evaluated using area under the curve (AUC) values based on 25%independent test data set. The results revealed that in addition to temperature, rainfall, and relative humidity, soil characteristics were affecting the geographical distribution of C. partellus and B. fusca at both the Mount Kilimanjaro and Taita Hills study sites. The relative importance of all studied variables varied between the two study sites. At Mount Kilimanjaro, WHc exhibited the greatest influence on C. partellus distribution while at Taita Hills it was relative humidity. For B. fusca distribution, the temperature was found more crucial at both Mount Kilimanjaro and Taita Hills. [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.

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.

Fusarium verticillioides and Busseola fusca are among the most significant biotic constraints to maize production in South Africa. In this study, the effect of B. fusca damage and mechanical wounding to maize ears on Fusarium ear rot development and fumonisin production was investigated. The effect of the interaction on Fusarium ear rot and B. fusca damage was studied by inoculating maize ears with F. verticillioides isolate MRC826 and infesting plant whorls with aliquots of 10–15 neonate larvae at the 12th leaf stage prior to tasselling. To simulate hail damage, maize ears were mechanically wounded at the blister stage with cork borers of different sizes and number of wounds, with and without F. verticillioides inoculation. Uninoculated, uninfested and undamaged control treatments were included. Field trials were conducted over three seasons using a randomised complete block design with six replicates per treatment. In all seasons, most Fusarium ear rot developed on ears inoculated with F. verticillioides . This study indicated that B. fusca infestation was not associated with higher Fusarium ear rot incidence in two of the three seasons. Moreover, B. fusca infestation was not associated with high fumonisin production in any season. This indicates that the presence of B. fusca was not highly associated with Fusarium ear rot or fumonisin production, possibly due to its characteristic feeding nature that causes sporadic wounds on maize ears, but also the strong impact of weather variability. Fusarium ear rot development and fumonisin production by F. verticillioides inoculum varied seasonally indicating the importance of environmental conditions on Fusarium ear rot and fumonisin production. Fusarium ear rot and fumonisin production significantly increased with the severity of cork borer wounding in both naturally infected and artificially inoculated maize ears. Therefore, the prevention of severe injuries to kernels, whether by mechanical damage or insects, should be considered as important in reducing Fusarium ear rot and fumonisin production in maize. [ABSTRACT FROM AUTHOR]

Interactions within and between species sharing the same resources are characterised by competition or facilitation, and can be influenced by factors such as larval numbers and phenotypic plasticity of the interactions. The effect of larval density on the survival and relative growth rate of the stemborers Busseola fusca ( Fuller) and Sesamia calamistis Hampson (both Lepidoptera: Noctuidae), and Chilo partellus ( Swinhoe) ( Lepidoptera: Crambidae) were studied, as well as the temporal plasticity of their competitive interactions. These stemborers attack maize crops ( Zea mays L.) ( Poaceae) in sub-Saharan Africa. Experiments were conducted in the laboratory under controlled conditions at the optimum development temperature (25 °C) for the three species. Surrogate stems filled with artificial diet were intra- and interspecifically infested with larvae of each species. The effect of larval density on competition was studied at low (six larvae) and high (12 larvae) levels of infestation, whereas the temporal plasticity of competition was evaluated at 7, 14, 21, or 28 days after infestation. The two experiments involved single- and multi-species infestation treatments. Larval numbers and wet mass in each artificial stem were recorded in each experiment. Survival and relative growth rate of the three species were significantly higher at low-infestation levels when facing either intra- or interspecific competition. The intensity of competition was also temporally plastic among the species and increased as the duration of competition increased. These results are discussed in terms of general infestations of cereal crops by borers. [ABSTRACT FROM AUTHOR]

Post-release monitoring of transgenic Bt maize fields for resistant pest populations is an important activity that will contribute to early identification and mitigation of resistance evolution by target pests. An effective Bt maize pest resistance monitoring programme relies on well-established baseline susceptibility data. The target pest of Bt maize in South Africa, Busseola fusca (Fuller) (Lepidoptera: Noctuidae), has evolved resistance to Bt maize expressing Cry1Ab proteins, with numerous reports of resistance from the highveld region of the country. Although Bt maize has been cultivated in the Eastern Cape province since 2001, no data exist on the resistance status of field populations of B. fusca to Bt maize in this region. In view of this, B. fusca larvae were collected from fields in two Bt maize cultivating areas and a non-Bt maize cultivating area of the Eastern Cape for laboratory assays to determine the level of susceptibility of B. fusca to Bt maize. Rearing colonies of each population were established and neonate larvae from each population were used to infest non-Bt maize plants, and Bt maize of events MON810 and MON89034. All larvae maintained on MON89034 died within seven days of infestation. Survival of all B. fusca populations maintained on MON810 declined rapidly during the first seven days and was significantly (P<0.001) lower than larval survival on non-Bt maize. Similarly, mass of surviving larvae of all populations on MON810 from the first two weeks to the 21st day was significantly (P < 0.001) lower than the mass of larvae on non-Bt maize. These results indicate that fieldcollected populations screened in this study are still susceptible to Bt maize. [ABSTRACT FROM AUTHOR]

The host recognition and acceptance behaviour of two braconid larval parasitoids (Cotesia sesamiae and C. flavipes) were studied using natural stemborer hosts (i.e., the noctuid Busseola fusca for C. sesamiae, and the crambid Chilo partellus for C. flavipes) and a non-host (the pyralid Eldana saccharina). A single larva was introduced into an arena together with a female parasitoid and the behaviour of the wasp recorded until it either stung the larva or for a maximum of 5 min if it did not sting the larva. There was a clear hierarchy of behavioural steps, which was similar for both parasitoid species. In the presence of suitable host larvae, after a latency period of 16-17 s, the wasp walked rapidly drumming the surface with its antennae until it located the larva. After location and antennal examination of the host, which lasted 60-70 s and 30 s, respectively, the parasitoid inserted its ovipositor. Stinging that resulted in successful oviposition usually lasted 5-6 s. In the presence of non-host larvae, the latency period was between 25-70 s, and parasitoids spent significantly more time walking and antennal drumming on larvae without ovipositing. It is likely that these two parasitoid species use their antennae for host recognition, and both their antennae and tarsi for final acceptance of a host for oviposition. In both C. sesamiae and C. flavipes tactile and contact-chemoreception stimuli from the hosts seemed to play a major role in the decision to oviposit.

Ecological intensification utilizes biodiversity to maintain agricultural yields while reducing negative environmental impacts. While pest management is a common goal of ecological intensification, studies examining ecologically intensified pest management systems over longer time scales are rare. Using the push-pull system in Western Kenya, we examine whether pest abundance (for both insects and parasitic weeds) and yield vary with time since a given push-pull field was established. With a total of 1880 data points from 476 unique farmers and 24 cropping seasons, we found that pests declined with time since establishment in both push-pull and nearby control fields, while yield improved with time since establishment in push-pull fields. Although this study did not directly address mechanisms, it seems likely that pests in the push-pull system are not successfully adapting to overcome its pest management effects given the continued declines in pest abundance over time. Our data suggest that ecologically intensified agriculture may be resilient against pest adaptation over time, maintaining consistently high yields. • An agroecological system for maize maintains benefits over several growing seasons. • Analysis included 1880 data points from 476 unique farmers and 24 cropping seasons. • The push-pull system's effects appear to become stronger with time. • Control fields near push-pull fields also have fewer pests as push-pull fields age. [ABSTRACT FROM AUTHOR]

Resistance evolution by target pests threatens the sustainability of Bt maize in Africa where insect resistance management (IRM) strategies are faced by unique challenges. The assumptions, on which current IRM strategies for stem borers are based, are not all valid for African maize stem borer species. The high dose-refuge strategy which is used to delay resistance evolution relies heavily on the presence of appropriate refuges (non-Bt plants) where pests are not under selection pressure and where sufficient numbers of Bt-susceptible individuals are produced to mate with possible survivors on the Bt maize crop. Misidentification of stem borer species and inaccurate reporting on wild host plant diversity over the past six decades created the perception that grasses will contribute to IRM strategies for these pests in Africa. Desired characteristics of refuge plants are that they should be good pest hosts, implying that larval survival is high and that it produces sufficient numbers of high-quality moths. Refuge plants should also have large cover abundance in areas where Bt maize is planted.While wild host plants may suffice in IRM strategies for polyphagous pests, this is not the case with stenophagous pests. This review discusses data of ecological studies and stemborer surveys conducted over the past decade and shows that wild host plants are unsuitable for development and survival of sufficient numbers of stem borer individuals. These grasses rather act as dead-end-trap plants and do not comply with refuge requirements of producing 500 susceptible individuals for every one resistant individual that survives on Bt maize. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to understand the spatio-temporal spread of the maize stem borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae) in smallholder maize farms. The analysis carried out allowed the establishment of complementary sampling scheme and analysis that can be applied to investigate the propagation of stem borer damages and extended to other insect pests. This approach requires consideration of all plants point locations, the knowledge on the level of damage and its characterization. Results showed that there was a two-week interval between occurrence of the peaks of leaf damage and male adult moth abundance. The prior role of leaf damages in the farm infestation by B. fusca is revealed, and an estimate of the mean transition time between different damage types is provided. Furthermore, damaged plants exhibited a local spatial autocorrelation within a range of dependence of 0-10 meters; and the spatio-temporal pattern of B. fusca damage spread evolves as a spiral around an initial patch of damaged plants. By assuming a neighbor configuration of distribution of damaged plants nearby non-damaged, we showed that the inner plants are likely to become damaged within a time period of a week; thus, B. fusca infests farms in a systematic fashion. Overall, these results have useful implications for improving and optimizing existing field sampling methods for insect pest damages. The approaches used in carrying out the analysis further provided a deep understanding helpful to improve integrated pest management (IPM) strategies against stem borers, and offer IPM practitioners’ the opportunity to design, develop, and implement optimum control methods against B. fusca , an important pest of maize in Africa. [ABSTRACT FROM AUTHOR]

A study was conducted to assess the performance of maize hybrids with Bt event MON810 ( Bt -hybrids) against the maize stem borer Busseola fusca (Fuller) in a biosafety greenhouse (BGH) and against the spotted stem borer Chilo partellus (Swinhoe) under confined field trials (CFT) in Kenya for three seasons during 2013–2014. The study comprised 14 non-commercialized hybrids (seven pairs of near-isogenic Bt and non- Bt hybrids) and four non-Bt commercial hybrids. Each plant was artificially infested twice with 10 first instar larvae. In CFT, plants were infested with C. partellus 14 and 24 days after planting; in BGH, plants were infested with B. fusca 21 and 31 days after planting. In CFT, the seven Bt hybrids significantly differed from their non-Bt counterparts for leaf damage, number of exit holes, percent tunnel length, and grain yield. When averaged over three seasons, Bt -hybrids gave the highest grain yield (9.7 t ha −1 ), followed by non- Bt hybrids (6.9 t ha −1 ) and commercial checks (6 t ha −1 ). Bt -hybrids had the least number of exit holes and percent tunnel length in all the seasons as compared to the non- Bt hybrids and commercial checks. In BGH trials, Bt -hybrids consistently suffered less leaf damage than their non-Bt near isolines. The study demonstrated that MON810 was effective in controlling B. fusca and C. partellus . Bt -maize, therefore, has great potential to reduce the risk of maize grain losses in Africa due to stem borers, and will enable the smallholder farmers to produce high-quality grain with increased yield, reduced insecticide inputs, and improved food security. [ABSTRACT FROM AUTHOR]

Genome size varies considerably among organisms, largely as the result of differences in the content of non-coding and/or repetitive DNA, such as introns, pseudogenes, or transposable elements, as well as whole-genome duplications. Genome size is known to correlate with metabolic rates. Because polyphagy also affects the metabolism, a correlation between diet specialization and genome size can be expected. To test this hypothesis, a study was undertaken with five closely related species of stem borers which are easy to rear under artificial conditions, namely Busseola fusca ( Fuller), Busseola segeta ( Bowden), Busseola nairobica Le Ru, Sesamia calamistis Hampson, and Sesamia nonagrioides Lefebvre (all Lepidoptera: Noctuidae). However, as the number of species was too low for correlating diet with genome size in Lepidoptera in general, literature data from 16 Lepidoptera species were used in addition. The results pointed to a relationship between genome size and the insect's host plant range in Lepidoptera, but below the family level only, with larger genomes in polyphagous compared to specialist species. In addition, the genome size appeared to be influenced not only by host plant range but also by environmental/climatic conditions. Studies to test this hypothesis should be done strictly below the family level. [ABSTRACT FROM AUTHOR]

In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus . Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca . [ABSTRACT FROM AUTHOR]

The African stem borer, Busseola fusca Fuller, is one of the most devastating insect pests of maize in tropical environments. Understanding of combining ability and heterosis may be useful for designing insect resistant hybrids. However, among the adapted maize inbred lines used in this study, the combining ability and heterotic orientation for grain yield and borer resistance is not known. The objective of this study was to determine combining ability and heterotic orientation of maize inbred lines under B. fusca infestation. Sixty six inbred lines were crossed to two single cross testers from CIMMYT in accordance with the line × tester mating scheme. The 132 three-way testcross hybrids and four checks were evaluated at two locations in Kenya. Data were analysed using PROC GLM of SAS statistical package. The genotypes × environment interactions were significant, therefore the two test locations were considered as ideal environments for genotype comparison. General combining ability effects were significant for B. fusca stem borer resistance and grain yield, suggesting a preponderance of the additive gene effects for borer resistance traits. Specific combining ability effects were significant for B. fusca borer resistance traits and grain yield indicating that non-additive effects were also influential. Based on grain yield heterosis data at Embu, 22 lines were allocated to group A, 18 to group B and 8 to group AB, while at Kakamega, 24 lines were oriented to group A, 13 to group B and 9 to group AB, whilst the remainder could not be classified. Based on the SCA effects, at Embu, 20 lines revealed positive SCA effects with both testers and were considered to be AB-oriented; while 12 and 7 lines were oriented towards A and B, respectively. A similar trend was observed at Kakamega but only one line exhibited positive SCA effects for grain yield with both testers, while the remainder had negative SCA effects. The identified lines and heterotic groups may be used by maize programmes that emphasize stem borer resistance in hybrids. [ABSTRACT FROM AUTHOR]

Stem borers, Busseola fusca and Chilo partellus, are among the key devastating lepidopteran insect pests of maize causing grain yield losses. Recurrent selection studies for stem borer resistance in maize are limited. However, maize populations carrying resistance genes to these stem borers have not been exploited fully in breeding programmes. The objective of the study was to separately improve resistance to B. fusca and C. partellus stem borers for two maize populations CML395/MBR C5 Bc and CML444/MBR/MDR C3Bc and therefore grain yield after two cycles of S1 progeny recurrent selection. Cycle 0 and the advanced generations (cycle 1-susceptible, cycle 1-resistant and cycle 2-resistant) were evaluated at three locations in Kenya using a 35 × 12 α-lattice design with 2 replications. The net reductions in cumulative tunneling, number of exit holes and leaf feeding damage scores ranged from 0 to 69 % for both populations after two cycles of selection. In the two populations, each cycle of selection for borer resistance improved grain yield by 0.5-0.8 t ha. Actual net gains in grain yield with reference to cycle 0 were 43 % for population CML395/MBRC5 Bc under B. fusca infestation and 70 % under C. partellus infestation. For population CML444/MBR/MDR C3Bc, the actual net gains in grain yield were 25 % under B. fusca infestation and 36 % under C. partellus infestation. The reductions in the injurious effects attributable to leaf feeding damage, cumulative stem tunneling and number of exit holes contributed towards the 43 and 70 % net genetic gain in grain yield under B. fusca and C. partellus infestation respectively, for both populations. Broad sense heritability (H) for grain yield ranged from 2 to 98 % in both maize populations. The study showed that two cycles of S1 progeny recurrent selection was effective in accumulating favourable alleles for B. fusca and C. partellus stem borer resistance. [ABSTRACT FROM AUTHOR]

The host plant range of pests can have important consequences for its evolution, and plays a critical role in the emergence and spread of a new pest outbreak. This study addresses the ecological genetics of the indigenous African maize stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae), in an attempt to investigate the evolutionary forces that may be involved in the recent host range expansion and establishment of this species in Ethiopian and southern African sugarcane. We used populations from Ethiopia, Zimbabwe, and South Africa to examine whether the host range expansion patterns shared by the Ethiopian and the southern African populations of B. fusca have evolved independently. Base-pair differences in the cytochrome oxidase I (COI) gene were used to characterize haplotype diversity and phylogenetic relationships. There were seven haplotypes among the 30 sequenced individuals collected on four host plant species from 17 localities in the four countries. Of the seven COI haplotypes identified, the two major ones occurred in both sugarcane and maize. Genetic analyses revealed no detectable genetic differentiation between southern African B. fusca populations from maize and sugarcane (FST=0.019; P=0.24). However, there was strong evidence of variation in genetic composition between populations of the pest from different geographic regions (FST=0.948; P<0.001). The main implication of these findings is that the B. fusca populations in maize in southern Africa are more likely to shift to sugarcane, suggesting that ecological opportunity is an important factor in host plant range expansion by a pest. [ABSTRACT FROM AUTHOR]

Napier grass,Pennisetum purpureum(Schumach), in combination with intercrops has been used successfully in habitat management for maize stem borers in Africa. The use of Napier grass only as a trap or barrier plant forChilo partellus(Lepidoptera: Crambidae) andBusseola fusca(Fuller) (Lepidoptera: Noctuidae) was evaluated in this study. Napier grass borders were planted only on two sides of small-scale farmers’ maize fields, since planting of perennial trap crops on all sides of fields hampered mechanical cultivation.C. partelluswas the dominant borer species, followed byB. fuscaandSesamia calamistis(Hampson) (Lepidoptera: Noctuidae). Reductions between 0% and 27.4% in the incidence of borer-infested plants were observed on the 16 farms evaluated in this study. The results show that Napier grass as trap/barrier crop suppresses stem borer numbers in maize fields. [ABSTRACT FROM PUBLISHER]

Lepidopteran stemborers, mainly the African stemborer Busseola fusca Fuller and spotted stemborer Chilopartellus Swinhoe, are among the economically important pests of sorghum in Kenya. Identification of sources of resistance is valuable for the development of an integrated pest management strategy to minimize losses. This study evaluated 27 genotypes with artificial infestations (mostly for tolerance) in two different agroecological zones. Data on damage from leaf feeding, dead heart, exit holes, and stem tunnelling; plant height; days to 50% flowering; total grain yield; and hundred-grain mass were collected. Significant differences (P< 0.001) were observed in all the traits evaluated, except leaf damage, under infestation by C. partellus. Classification into different categories of resistance revealed genetic variation. Genotypes resistant/moderately resistant to both pests were as follows: ICSA 464>ICSB 464>ICSB 467>ICSA 472>ICSB 472>ICSA 473>ICSA 474>IESV 91131 DL>Macia. The relative contributions of the damage parameters to grain yield loss were partitioned into direct and indirect relationships by path coefficient analysis with grain yield as the resultant variable. The results revealed that damage from exit holes, dead heart, leaf feeding and stem tunnelling had a negative indirect effect on grain yield. The identified genotypes can be used to enhance resistance to both pests in susceptible cultivars that farmers prefer. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied effects of push–pull and landscape complexity on stemborer population and parasitism. [•] Pest abundance in maize increased with increasing grassland cover in the landscape. [•] Natural enemy activity was unaffected by landscape complexity. [•] Push–pull system suppressed stemborer colonization and enhanced larval and pupal parasitism. [•] There was an interactive effect of local management and landscape complexity on pest abundance. [ABSTRACT FROM AUTHOR]