Field resistance in maize cultivars to stem borer Chilo partellus

The Kenyan maize varieties, Hybrid 511, Hybrid 622, Pwani hybrid, Katumani Composite B, and local populations were evaluated along with the varieties of Multiple Insect-Resistant Tropical (MIRT) pool and experimental varieties from The Maize and Wheat Improvement Centre (CIMMYT), Mexico for resistance to the stem borer, Chilo partellus (Swinhoe). The artificial infestation by first-generation C. partellus on maize during the early whorl stage revealed that the leaf feeding damage, the dead heart formation, and the stem damage on the Kenyan hybrids and populations were significantly greater than on the MIRT varieties. The experimental varieties of CIMMYT were also susceptible to C. partellus. When the maize was infested at anthesis, the Kenyan varieties displayed a moderate level of resistance in terms of stem tunnelling and grain damage by C. partellus. The varieties of Multiple Insect Resistance Tropical pool can be effectively used by the breeders to enhance the resistance of agronomically good, but susceptible, varieties of Kenya.     

Distribution,relative importance,and agro-climatic preferences of cereal stem borers in Eastern Ethiopia

Abstract

The distribution and relative importance of lepidopteran stem borers attacking maize and sorghum were investigated in farmers’ fields during the main cropping seasons of 2015 and 2016 across three main agro-climatic zones (ACZs) of eastern Ethiopia. Three stem borer species, namely Busseola fusca Fuller, Chilo partellus Swinhoe and Sesamia calamistis Hampson were found attacking these crops with different levels of distribution and abundance among ACZs. Busseola fusca was the only borer species in the highlands and dominant (67%) in the midhighland zones, while C. partellus was predominant (75%) in the lowlands. The abundance of S. calamistis was low across its distribution range. Across both years, mean plant infestation by B. fusca ranged from 20.38 in lowlands to 42.97% in highlands. Chilo partellus resulted in a mean infestation of 27.38% in the midaltitude to 68.24% in lowlands. Mean density of larvae per plant was higher for C. partellus (2.85), followed by B. fusca (1.41) and S. calamistis (0.46). Moreover, within each ACZs, variation in plant damage variables was observed between the study periods. These spatio-temporal differences in community structures of stem borers are discussed particularly in relation to agro-climatic requirements.     

Effects of water stress, nitrogen stress and certain sensory stimuli on infestation and damage by Chilo partellus (Swinhoe) to maize

Foliar, stalk and dead heart damage caused by Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) to several maize genotypes (Inbred A, MBR 8637, Poza Rica 7832, ER-29SVR, Across 7844, Bulk CG 4141, MMV 600 and ICZ2-CM) subjected to water stress were significantly lower than those observed when plants were grown in the absence of water stress. Resistance of maize genotypes to C. partellus was distinguished clearly when there was no water stress to the plants. Resistance/susceptibility of maize genotypes Inbred A, MMV 400, MBR 8637 and Poza Rica 7832 to C. partellus was the same at 0, 60, 90 and 120 kg of N per hectare. At each nitrogen level, the genotypes MMV 400, MBR 8637 and Poza Rica 7832 suffered significantly lower damage than the susceptible Inbred A. The humidity stimuli from maize plants and the olfactory/hygro stimuli from the plants infested with larvae were the most important factors affecting host plant selection by ovipositing C. partellus females.     

Assessment of the impact of natural enemies on stemborer infestations and yield loss in maize using selected insecticides in Mozambique

The effect of natural enemies on stemborer infestations and maize grain yields was estimated using an insecticide exclusion method. Field experiments were conducted at low, mid and high elevation zones, which vary in the stemborer species composition. Dimethoate was applied to exclude natural enemies and Cypermethrin to suppress stemborers, while other plots served as control. At all study sites more stemborer larvae and pupae were collected when natural enemies were excluded. Parasitism as well as maize grain weight in the unprotected plots were significantly higher than in the exclusion plots. Yield losses increased by 28.9 % in unprotected to 43.3 % in exclusion plots. The most abundant parasitoids of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) were Cotesia sesamiae (Cameron), Cotesia flavipes Cameron (Hymenoptera: Braconidae) and Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae). While for Busseola fusca (Fuller) (Lepidoptera: Noctuidae) they were C. sesamiae, Sturmiopsis parasitica (Curran) (Diptera: Tachinidae) and Porcerochasmias nigromaculatus Heinrich (Hymenoptera: Ichneumonidae). It was concluded that exclusion of natural enemies caused an increase in stemborer populations, thus, the parasitoids play an important role in suppressing stemborer infestations and increase maize yield.     

Multiparasitism by the pupal parasitoids, Xanthopimpla stemmator (Hymenoptera: Ichneumonidae) and Pediobius furvus (Hymenoptera: Eulophidae) on two African cereal stemborers, Chilo partellus (Lepidoptera: Crambidae) and Busseola fusca (Lepidoptera: Noctuidae)

The outcome of multiparasitism by two pupal parasitoids, the exotic solitary ichneumonid Xanthopimpla stemmator and the indigenous gregarious eulophid Pediobius furvus, was studied using the invasive crambid stem borer Chilo partellus and the indigenous noctuid Busseola fusca as hosts. Two parasitism sequences were observed, where X. stemmator oviposited before P. furvus, and vice versa. In addition, the effect of time between first and second parasitism on parasitoid emergence, development, sex ratio, and number of offspring was assessed. For most treatments, time interval between parasitism had no significant effect on the percentage if pupae producing either P. furvus or X. stemmator. In general, X. stemmator outcompeted P. furvus irrespective of the order of oviposition, time interval between ovipositions and host species. Further studies, especially on host finding capacity of the two parasitoid species are required to determine the competitiveness of the two species under field conditions.     

The effect of grassy field margins and fertilizer on soil water,plant nutrient levels,stem borer attacks and yield of maize in the humid forest zone of Cameroon

Two field experiments, planted in a split plot design, were conducted during 2002 in the forest zone of Cameroon, to investigate the effect of border rows with Pennisetum purpureum (Poaceae) or with Panicum maximum (Poaceae) on soil water, plant nitrogen (N), phosphorus (P) and potassium (K), borer infestations, parasitism and maize yield. The grassy boundaries were the main plots and fertilizer treatment the sub plots. Soil humidity was significantly higher under the grass borders than in maize plots. Nitrogen uptake by maize tended to be highest in plots surrounded by P. purpureum but the differences were significant during the second season only. Busseola fusca (Fuller) (Lepidoptera: Noctuidae) was the predominant borer species followed by Eldana saccharina (Walker) (Lepidoptera: Pyralidae). The predominant parasitoid species was the scelionid egg parasitoid Telenomus busseolae Gahan (Hymenoptera: Scelionidae). During both seasons, plant nitrogen, B. fusca infestation, plant damage and yield were significantly higher in maize sub-plots that received fertilizer The interaction between the grassy margin effect and the fertilization was significant only for B. fusca infestations, during the second season with maize + P. purpureum having a significantly lower number of borers in the fertilized than the unfertilized sub-plots. The grassy borders had no effect on B. fusca egg parasitism variables except in the first season, when maize with P. purpureum had a significantly higher percentage of egg batches parasitized. During both seasons, there were some significant differences in yield variables between main plots but the trends were not clear. Multiple regression showed that B. fusca infestation, plant damage, egg parasitism, plant N, P and K affected yield, with plant nutrients explaining most of the variability. The implication of the findings for the feasibilty of this habitat management technology to farmers in southern Cameroon is discussed.     

Hibernation by the lepidopteran stalk borers, Busseola fusca and Chilo partellus on grain sorghum

The lepidopteran stalk borers, the indigenous Busseola fusca (Fuller) (Noctuidae), and the exotic Chilo partellus (Swinhoe) (Pyralidae), were studied in grain sorghum fields, Sorghum bicolor (L.) Moench (cultivar SSK-52), in the dry season of 1986 (April–October) at Delmas and Brits, Transvaal, South Africa. More than 90% of plants at both sites were infested, but as winter progressed, the proportion of plants infested and the level of infestation dropped gradually. The borer larvae hibernated inside the dry stalks, but the location differed: 65% of B. fusca were in the lower third and 30% in the middle third, whereas for C. partellus it was 45 and 50% respectively. Both borers overwintered as larvae in either of the last three instars, but the proportions of larval instars were different. About 82% of B. fusca hibernated as 6th and 16% as 5th larval instars whereas with C. partellus it was 40 and 45% respectively. C. partellus started to emerge from diapause in the second part of August and it lasted until the first week of November, a period of 12 weeks, but with B. fusca on the other hand pupation lasted only 3 weeks during October–November. Parasitism was low on both species, but higher on B. fusca. Three parasites, Chelonus curvinaculatus Cameron, Chelonus sp. and Pristomerus sp. hibernated in the borers, one parasite Iphiaulax sp., hibernated in its cocoon inside the stalks, and two parasites Apanteles sesamiae Cameron and Bracon sp. were active in winter. Two ants, Pheidole megacephala Febricius, and Dorylus helvolus (L.), preyed on the borer larvae in winter.

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Hibernation des chenilles de deux espèces de mineuses, Busseola fusca et Chilo partellu dans les tiges de Sorghum bicolor

Résumé Deux chenilles mineuses de tiges, B. fusca, Noctuidae indigène, et C. partellus, Pyralidae exotique, ont été étudiées dans des champs de S. bicolor (cultivar SSK-52), pendant la saison sèche de 1986 (Avril–Octobre) à Delmas et Brits, au Transvaal en Afrique du Sud. Plus de 90% des pieds des deux stations étaient infestés, mais plus l'hiver avançait, plus la proportion de plantes in festées et le taux d'infestation diminuaient. Les chenilles ont hiverné dans les tiges sèches, mais leurs positions étaient différentes: 65% des B. fusca étaient dans le tiers inférieur et 30% dans le tiers médian, tandis que pour C. partellus, il s'agissait respectivement de 45 et 50%. Les duex chenilles hivernaient à l'un des 3 derniers stades larvaires, mais les proportions étaient différentes. Pour B. fusca environ 82% hivernaient au 6ème stade et 16% au 5ème stade, tandis que pour C. partellus c'étaient 40 et 45% respectivement. C. partellus a commencé à sortir de diapause pendant la seconde moitié d'Août et a continué jusqu'à la première semaine de Novembre, soit durant une période de 12 semaines, mais avec B. fusca la nymphose a duré seulement 3 semaines en Octobre–Novembre. Le parasitisme des deux espèces a été faible, mais plus important chez B. fusca. Trois parasites, Chelonus curvimaculatus Cameron, Chelonus sp. et Pristomerus sp. ont hiverné dans leurs cocons à l'intérieur des tiges, et deux parasites, Apanteles sesamiae Cameron et Bracon sp. étaient actifs en hiver. Deux fourmis, Pheidole megacephala Fabricius et Dorylus helvolus L. capturaient des chenilles de ces mineuses pendant l'hiver.

     

Duration of diapause in the stem borers, Busseola fusca and Chilo partellus

The duration of diapause in the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) was studied in South Africa by collecting diapausing larvae from the field throughout winter (April–August). B. fusca larvae emerged as moth around the middle of October regardless of the date of collection and the length of time they were kept in the laboratory under constant 21 °C. C. partellus larvae collected in April–June emerged in November, those collected in July emerged in October, and those collected in August emerged in September. Regardless of the collection date C. partellus started to emerge from diapause earlier and moth emergence lasted up to twice as long as in B. fusca. Under laboratory conditions at 60% RH both borer larvae lost about 50% of their body mass during diapause. When provided with water B. fusca larvae lost about 30% of their body mass and adults emerged 20 days earlier than when kept dry. C. partellus, on the other hand, lost only 13% of their body weight and emerged 34 days earlier. The differences between the two species are discussed in light of different types of diapause; i.e., obligatory diapause in B. fusca and facultative diapause in C. partellus.     

Species diversity of lepidopteran stem borer parasitoids in cultivated and natural habitats in Kenya

Field surveys were conducted during 2005 to 2007 to assess the species diversity of stem borer parasitoids in cultivated and natural habitats in four agroecological zones in Kenya. In total, 33 parasitoid species were recovered, of which 18 parasitized six stem borer species feeding on cereal crops, while 27 parasitized 21 stem borer species feeding on 19 wild host plant species. The most common parasitoids in cultivated habitats were Cotesia flavipes Cameron, Cotesia sesamiae (Cameron), Pediobius furvus Gahan and the tachinid Siphona sp., whereas in natural habitats, Siphona sp. was the most common. The majority of parasitoids were stenophagous species; only five species –Cotesia sp., Enicospilus ruscus Gauld and Mitchell, Pristomerus nr. bullis, Sturmiopsis parasitica (Curran) and Syzeuctus ruberrimus Benoit – were monophagous. In both cultivated and natural habitats, parasitoid species diversity was highest on the most dominant stem borers Busseola spp. and Chilo spp. On cereal crops, parasitoid diversity was highest on maize and among wild host plants, it was highest on Setaria spp. The ingress‐and‐sting attack method was the most common strategy used by parasitoids in both habitats. In all agroecological zones, parasitoid species diversity was significantly higher in natural than in cultivated habitats. Furthermore, the majority of parasitoid species were common to both cultivated and natural habitats. It was concluded that natural habitats surrounding cereal crops serve as refugia for sustaining the diversity of stem borer parasitoids from adjacent cereal fields.     

The effect of abscisic acid on cell growth, cell division and DNA synthesis in the maize root meristem

Cis -abscisic acid (ABA), when applied to maize ( Zea mays L. cv. LG 11) roots, decreases the rates of cell growth and cell division in the meristem. It also decreases the rate at which nuclei become labelled with [³H]-thymidine and enter mitosis. Removing the root cap accelerates the entry of nuclei into the DNA synthetic phase of the mitotic cycle and enhances the rate of cell proliferation in the quescent centre. ABA diminishes these effects, but does not suppress them. Thus, ABA cannot wholely substitute for the presence of a cap. One of the primary effects of applied ABA is to retard cell enlargement which may in turn affect the rate of cell division; natural endogenous ABA may act similarly. ABA might in this way assist in maintaining the quiescent centre in intact roots, but cannot be the sole agent involved.     

Phylogeography and population genetics of the maize stalk borer Busseola fusca (Lepidoptera, Noctuidae) in sub-Saharan Africa

The population genetics and phylogeography of African phytophagous insects have received little attention. Some, such as the maize stalk borer Busseola fusca, display significant geographic differences in ecological preferences that may be congruent with patterns of molecular variation. To test this, we collected 307 individuals of this species from maize and cultivated sorghum at 52 localities in West, Central and East Africa during the growing season. For all collected individuals, we sequenced a fragment of the mitochondrial cytochrome b. We tested hypotheses concerning the history and demographic structure of this species. Phylogenetic analyses and nested clade phylogeographic analyses (NCPA) separated the populations into three mitochondrial clades, one from West Africa, and two--Kenya I and Kenya II--from East and Central Africa. The similar nucleotide divergence between clades and nucleotide diversity within clades suggest that they became isolated at about the same time in three different refuges in sub-Saharan Africa and have similar demographic histories. The results of mismatch distribution analyses were consistent with the demographic expansion of these clades. Analysis of molecular variance (amova) indicated a high level of geographic differentiation at different hierarchical levels. NCPA suggested that the observed distribution of haplotypes at several hierarchical levels within the three major clades is best accounted for by restricted gene flow with isolation by distance. The domestication of sorghum and the introduction of maize in Africa had no visible effect on the geographic patterns observed in the B. fusca mitochondrial genome.     

Characterization of eight microsatellite loci in the maize stalk borer Busseola fusca Fuller, 1901 (Lepidoptera: Noctuidae)

The noctuid stem borer Busseola fusca occurs throughout sub‐Saharan Africa, where it is considered as a major pest of corn and sorghum. To understand B. fusca phylogeography, we isolated and characterized eight microsatellite loci in this species. We investigated these loci for polymorphism on a subset sample of individuals from different geographic populations. All loci were polymorphic, showing between four and 10 alleles. Cross‐species amplification of four of these loci was tested on 11 other noctuid species.     

Calyx fluid proteins of two Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) biotypes in Kenya: implications to biological control of the stem borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae)

Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) is an indigenous larval endoparasitoid of Busseola fusca (Fuller) (Lepidoptera: Noctuidae) in sub-Saharan Africa. In Kenya, reports suggest that C. sesamiae occurs as two biotypes. Biotype avirulent to B. fusca gets encapsulated by haemocytes in this host and is unable to complete development. Biotype virulent to B. fusca is able to overcome immune defences. Factors present in the calyx fluid such as the PolyDNAviruses (PDV), venom and calyx fluid proteins have been implicated in the variation of C. sesamiae virulence against B. fusca. In the present study, calyx fluid proteins of the two C. sesamiae biotypes were compared using 2-D gel electrophoresis. More protein spots were observed in the virulent parasitoid calyx fluid, but some proteins were specifically observed in the avirulent parasitoid calyx fluid while others were observed in both. To study changes in proteins due to parasitism of B. fusca larvae by the two strains, SDS-PAGE gel were performed on fat body tissues and the haemolymph at three time points. Differences between the two strains were observed in both the fat body and haemolymph tissues. Parasitism-specific protein bands were detectable in fat body tissues of B. fusca larvae parasitized by the two C. sesamiae strains. These proteins were absent in unparasitized larvae. Implications for using C. sesamiae as a biocontrol agent of B. fusca in Africa are discussed.     

Diversity and abundance of wild host plants of lepidopteran stem borers in two different agroecological zones of Kenya

A survey was carried out between 2004 and 2005 in two ecologically different locations, Kakamega and Muhaka to assess diversity and abundance of wild host plants of lepidopteran stem borers as compared to maize plots during the cropping and non-cropping seasons. Kakamega in Western Kenya is characterized by a Guineo-Congolian rain forest mosaic and Muhaka at the Kenyan coast by a Zanzibar Inhambane mosaic with secondary grassy and woody vegetation. In Kakamega, wild host plants and maize covered 2 and 43% of the surveyed area. No variation in diversity and relative abundance of wild host plants was observed between both the cropping and non-cropping seasons. In Muhaka, the diversity and relative abundance of wild host plant species differed between seasons, with the Shannon Weaver Index (H) of 1.67 and 0.95 for cropping and non-cropping seasons, respectively. Similarly in this location, wild host plant cover varied between cropping (23%) and noncropping (17.9%). During both seasons, this was higher than the maize cover, with 10.7% and 0% for the cropping and non-cropping seasons, respectively. For both localities, the implication of the differences found in the abundance and diversity between the cropping and non-cropping seasons is discussed.     

The role of wild host plants in the abundance of lepidopteran stem borers along altitudinal gradient in Kenya

Presence of wild host plants of stem borers in cereal-growing areas has been considered as reservoirs of lepidopteran stem borers, responsible for attack of crops during the growing season. Surveys to catalogue hosts and borers as well as to assess the abundance of the hosts were carried out during the cropping and non-cropping seasons in different agro-ecological zones along varying altitude gradient in Kenya. A total of 61 stem borer species belonging to families Noctuidae (25), Crambidae (14), Pyralidae (9), Tortricidae (11) and Cossidae (2) were recovered from 42 wild plant species. Two noctuids, Busseola fusca (Fuller), Sesamia calamistis Hampson, and two crambids, Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) were the four main borer species found associated with maize plants. In the wild, B. fusca was recovered from a limited number of host plant species and among them were Sorghum arundinaceum (Desvaux) Stapf, Setaria megaphylla (Steudel) T. Durand & Schinz, Arundo donax L. and Pennisetum purpureum Schumacher. In contrast, the host range of C. partellus was considerably wider [13 for S. calamistis]. However, the number of larvae of these species was lower in the wild compared to cultivated fields, thus the role of natural habitat as a reservoir for cereal stem borers requires further studies. Importance of the wild host plants as well as borer diversity along the altitudinal gradient is discussed.     

Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the teveis of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize ( Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature, however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.     

Species richness and parasitism in an assemblage of parasitoids attacking maize stem borers in coastal Kenya

Abstract. 1. Parasitoids were reared from four species of lepidopteran stem borer collected in maize in southern coastal Kenya from 1992 to 1999. The stem borers included three native species, Sesamia calamistis Hampson, Busseola fusca Fuller, and Chilo orichalcociliellus (Strand), and one exotic borer, Chilo partellus (Swinhoe). A total of 174 663 caterpillars was collected, of which 12 645 were parasitised.
2. Twenty-six primary parasitoid species were reared from the exotic borer, C. partellus , indicating a rapid accumulation of native parasitoids on the alien borer.
3. The three most abundant parasitoids were the larval parasitoids Cotesia sesamiae Cameron, Cotesia flavipes (Cameron), and the pupal parasitoid Pediobius furvus Gahan. The pupal parasitoid Dentichasmias busseolae Heinrich and the larval parasitoid Goniozus indicus Ashmead were also common. All used an ingress-and-sting method of attack.
4. Cotesia flavipes , introduced into Kenya in 1993, was found in all seasons from 1997 onwards, and has become the most abundant stem borer larval parasitoid in the area. A native congener, Cotesia sesamiae , appeared in all seasons from 1992 to 1999. Together, these two parasitoids accounted for 83.3% of the parasitised borers.
5. Thirty parasitoid species were recovered in Kilifi district, 27 in Kwale, and 15 in Taita Taveta. Parasitism was much greater in Taita Taveta district than in Kilifi or Kwale districts.     

Larval dispersal of the invasive fall armyworm,Spodoptera frugiperda,the exotic stemborer Chilo partellus,and indigenous maize stemborers in Africa

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.     

Diversity and abundance of lepidopteran stem borers and their host plants in Ethiopia

Lepidopteran stem borers are among the most important insect pests of maize, sorghum and sugarcane in sub‐Saharan Africa. Except for Chilo partellus, the other stem borer pests in Ethiopia are indigenous to Africa and are assumed to have coevolved with some native grasses and sedges in the natural habitat. In addition to pest species, natural habitats harbour diverse non‐economic stem borer species, some of which are new to science. However, with the growing threats to natural habitats, some non‐economic stem borer species may switch or expand their host ranges to include cultivated crops and evolve as “new” pests. Besides host switch, some of the unknown species currently limited to natural habitats may disappear. We examined the diversity, abundance and interactions of lepidopteran stem borers and their wild host plants in five different vegetation mosaics in Ethiopia. The stem borer species diversity varied among vegetation mosaics and host plants. Forty‐four stem borer species belonging to 14 different genera in the families of Noctuidae, Crambidae, Pyralidae and Tortricidae were recorded from 34 wild host plants and through light trap. Among these families, Noctuidae was the highest in species richness in which 31 species were identified, out of which 15 species and two genera were new to science. This paper discusses the ecological interpretation of host plant–stem borer species interactions, particularly in relation to habitat disturbances.