Stem Borer Species Research Articles

Relationships of Reproductive Traits With the Phylogeny of the African Noctuid Stem Borers.

The display of the reproductive behavior in most noctuid Lepidoptera follows a diel periodicity and is limited to a precise period of either the day or the night. These behavioral traits and the sex pheromone chemistry can be species specific and thus might be linked to the phylogeny. The objective of this study was to test the relationship of these reproductive traits with phylogeny. The study was undertaken using eight closely related species of noctuid stem borers, which are easy to rear under artificial conditions, namely, Busseola fusca, B. nairobica, B. sp. nr. segeta, Manga melanodonta, M. sp. nr. nubifera, Pirateolea piscator, Sesamia calamistis, and S. nonagrioides. For each species, the adult emergence period, the mating time, and the oviposition period were estimated, referred as biological traits. The components of the sex pheromones emitted by the females of each species were also analyzed by gas chromatography–mass spectrometry. Among the biological traits measured, only those linked to the oviposition pattern (timing and egg loads per night) were significantly correlated with the phylogeny of these species. For the sex pheromone components, among the 13 components identified in all species, only four, namely, Z9-tetradecenyl acetate (Z9-TDA), Z11-TDA, E11-TDA, and Z11-hexadecenyl acetate (Z11-HDA), showed the highest significant correlations with the phylogeny. These results suggest that among the different reproductive traits evaluated, only few are phylogenetically constrained. Their involvement in the reinforcement of ecological speciation in noctuid stem borers is discussed.

Influence of Dietary Experience on the Induction of Preference of Adult Moths and Larvae for a New Olfactory Cue.

In Lepidoptera, host plant selection is first conditioned by oviposition site preference of adult females followed by feeding site preference of larvae. Dietary experience to plant volatile cues can induce larval and adult host plant preference. We investigated how the parent’s and self-experience induce host preference in adult females and larvae of three lepidopteran stem borer species with different host plant ranges, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and the monophagous Busseola nairobica, and whether this induction can be linked to a neurophysiological phenotypic plasticity. The three species were conditioned to artificial diet enriched with vanillin from the neonate larvae to the adult stage during two generations. Thereafter, two-choice tests on both larvae and adults using a Y-tube olfactometer and electrophysiological (electroantennography [EAG] recordings) experiments on adults were carried out. In the polyphagous species, the induction of preference for a new olfactory cue (vanillin) by females and 3rd instar larvae was determined by parents’ and self-experiences, without any modification of the sensitivity of the females antennae. No preference induction was found in the oligophagous and monophagous species. Our results suggest that lepidopteran stem borers may acquire preferences for new olfactory cues from the larval to the adult stage as described by Hopkins’ host selection principle (HHSP), neo-Hopkins’ principle, and the concept of ‘chemical legacy.’

Correlation between agronomic and stem borer resistant traits in maize: Implications in selection

Objective : The interrelationship between agronomic and resistant traits of two stem borer species, and its influence on selection was studied in a yellow maize population, DMR ESR-Y, at Ibadan between 2009 and 2010. Methodology and results: Two hundred and fifty (250) full-sib progenies of the population with three checks were evaluated. Resistant traits had negative correlations with most agronomic traits including grain yield (GY). GY had significant relationship with days to 50% pollen shed, (DTA) (rg = 0.49**), plant height (PH) (rg = 0.46**) and ear aspect (EA) (rg = -0.98**). Indirect selection of GY via DTA and PH gave gains that were a little lower than direct selection for GY, but they have higher heritability. Indirect selection of stem tunnelling and cob damage through EA would give gains of 150.64 % and 106.94 % respectively. Conclusion and application of results : This result suggested that either days to 50% pollen shed or plant height could be considered in selection for stem borer resistance. Ear aspect is another good criterion to consider instead of cob damage and stem tunnelling to hasten selection. The result indicated that breeders selecting for stem borer resistance and high yield could consider plant height, days to 50% pollen shed, ear aspect and grain yield itself as criteria for selection. In selecting the best genotypes in any crop improvement study therefore, breeders need to consider not only the magnitude of the correlation between pairs of traits, but the desirability of their relationship, ease of measuring the traits, correlated response among the traits, and heritability of the secondary trait selected. Keywords : Correlated responses, heritability, secondary traits, selection, stem borer resistance

Geometric Morphometric Analysis of Population Differentiation in Two Species of Stem Borers from Bohol, Philippines

Stem borers are one of the most important insect pests that could infest rice plants from seedling to maturity and thus play a major role in crop losses. The study of its mandible that is used in feeding of stem borer would help understand the mechanisms and variations that could affect the adaptation and modification affecting severity of infestation. In this study, the mandible of two population of stem borers, the yellow stem borer (Scirpophaga incertulas and the striped stemborer (Chilo suppressalis) in three rice varieties IR-66, Pioneer 77 and Bigante were used to analyze the adaptation with regards to mandible shape in relation to rice variety in the same geographical location using outline-based (elliptic Fourier) geometric morphometric (GM) analysis to determine the shape variations in the left and right mandible of two population of stem borers. Further, scatter plot method was used to illustrate variations in the shapes of the mandibles between populations. Results of this study showed symmetrical shape variations in the right and left mandible of the two species of stem borers and their accumulation to the kind of rice plant varieties were not selective. Keywords - Animal ecology, stem borer, mandible, geometric morphometric analysis,Philippines

Abundance and Spatial Dispersion of Rice Stem Borer Species in Kahama, Tanzania.

Species diversity, abundance, and dispersion of rice stem borers in framer’s fields were studied in four major rice growing areas of Kahama District. Stem borer larvae were extracted from the damaged tillers in 16 quadrants established in each field. Adult Moths were trapped by light traps and collected in vials for identification. Results indicated the presence of Chilo partellus, Maliarpha separatella, and Sesamia calamistis in all study areas. The most abundant species was C. partellus (48.6%) followed by M. separatella (35.4%) and S. calamistis was least abundant (16.1%). Stem borers dispersion was aggregated along the edges of rice fields in three locations (wards) namely: Bulige, Chela, and Ngaya. The dispersion in the fourth ward, Kashishi was uniform as established from two of the three dispersion indices tested. Further studies would be required to establish the available alternative hosts, the extent of economic losses and the distribution of rice stem borers in the rest of the Lake zone of Tanzania.

Aboveground Arthropod Composition, Abundance and Guild Structure in Upland Rice Agro-ecosystem at Matalam, North Cotabato, Philippines

With the recent innovations in the field of ecological pest management,conservation and enhancement of biological diversity at any rice agro-ecosystemshas received considerable attention. The composition and abundance ofaboveground arthropods was assessed on upland rice fields in Matalam, NorthCotabato, Southern Mindanao, Philippines. Sampling and monitoring was doneusing malaise trapping, sweep netting and direct counting techniques. A total of29 arthropod species belonging to 21 families in nine orders were documented.The collected samples were comprised of 40% insect pests, 53% predators and7% parasitoids. The three most abundant insect pests were rice bug (Leptocorisaoratorius), rice seedling maggot (Atherigona oryzae), and pink stemborer (Sesamia inferens). The predators are dominated by lady bird beetle (Micraspis spp.), social wasp (unknown) and long-jawed spider (Tetragnatha maxillosa). Ichneumonids,Braconids and Tachinids, though in smaller numbers, were present throughoutthe cropping season. More importantly, the study reported the presence of four rice stem borer species – Scirpophaga innotta, Scirpophaga incertulas, Sesamia infere and Chilo suppressalis and two rice grain bug species – Paraeucosmetuspallicornis and Elasmolomus sordidus in Matalam. The occurrence, compositionand abundance of insect pests and associated natural enemies vary with ricegrowth and developmental stages. The negative Pearson’s correlation coefficient (r= -0.31) between the insect pests and natural enemies was attributed to effectivecultural management practices which have been developed through decades ofsubsistence upland rice farming.Keywords: Ecology, aboveground arthropods, upland rice agro-ecosystem, sampling andmonitoring, Philippines

Biology and Development ofSturmiopsis parasitica(Diptera: Tachinidae) on Different Species and Populations of Maize Stemborers in Zimbabwe and an Assessment of Its Suitability for Redistribution in Africa

The tachinid larval parasitoid Sturmiopsis parasitica (Curran) has a wide distribution in eastern, southern and West Africa where it attacks several species of cereal stemborers. Its development on Busseola fusca Fuller (four populations), Chilo partellus (Swinhoe) and Sesamia calamistis Hampson was evaluated in Zimbabwe in the laboratory. The parasitoid's larviposition patterns and ways to induce its early emergence from diapausing host larvae inside which it overwinters were also studied. Irrespective of the inoculation method used, the four B. fusca populations were equally suitable for parasitoid development. Chilo partellus was a partially suitable host while S. calamistis was completely unsuitable. Mated female parasitoids commenced larviposition at eight days after mating, with a peak being attained on day 15. Placing field-collected diapausing B. fusca larvae in fresh maize stems or in moistened dry stems could bring forward the emergence of S. parasitica from diapausing hosts. The implications of the current findings on the suitability of S. parasitica as a redistribution candidate in Africa are discussed.

Selective enhancement of parasitoids of rice Lepidoptera pests by sesame (Sesamum indicum) flowers

Rice is one of the most important global crops but, despite suffering serious insect pest damage, has been less the subject of conservation biological control research compared with crops of importance in developed countries. Earlier studies of sesame (Sesamum indicum) as a nectar plant grown on the bunds around rice crop to promote natural enemies of rice pests had focused on the natural enemies of planthopper pests. But there is little available information on the effects of this plant’s nectar on parasitoids of important rice stem borer pests, or on the extent to which sesame may be a selective food plant such that adult Lepidoptera do not feed on its nectar. The present laboratory study assessed the effect of sesame flowers on Apanteles ruficrus, Cotesia chilonis and Trichogramma chilonis and their stem borer hosts, Sesamia inferens and Chilo suppressalis. Adult survival of all parasitoid species was increased by the presence of S. indicum flowers compared with a water control. Realized fecundity of T. chilonis was significantly enhanced by sesame flowers. Egg production of both stem borer species was comparable for S. indicum and the water treatment, and significantly lower than the honey solution control. The same trend, illustrating lack of benefit from access to sesame nectar, was also apparent in adult longevity of C. suppressalis. These findings indicate that sesame is a selective food plant that is unlikely to promote key Lepidoptera pests of rice when used in the field though it does benefit parasitoids representing three genera.

Diversity and Host Range of Lepidopteran Stemborer Species in Cameroon

Lepidopteran stemborers are among the most important field insect pests of cereal crops in sub-Saharan Africa. With the exception of Chilo partellus, all other borer pests are indigenous to Africa and are assumed to have co-evolved with some native grasses and sedges. Understanding the interactions between pest species and their cultivated and native hosts are required to develop sustainable management strategies. In addition to pest species, natural habitats support diverse range of species (non-pests and their associated natural enemies) some of which are unknown to science. Although the stemborer—host plant interactions have been well described for eastern and southern Africa, knowledge regarding distribution and diversity of stem borer species and their host plants in western and Central Africa is limited. Existing knowledge of the stemborer species diversity of these regions indicate a lower specific and generic diversity compared to eastern and southern Africa. There is need to undertake extensive s...

Identification and Distribution of Sugarcane Stem Borer in Bangladesh

Field surveys were conducted during the cropping season of 2010-2011 to assess the distribution of Sugarcane stem borer species in 12 AEZs of Bangladesh. These surveys documented abundance and their distribution and results clearly showed the existence of the stem borer at all locations surveyed, but with a higher incidence in the Atwary (36%) and initiation of infestation was observed on 20 May. Stem borer incidence and distribution varied significantly among the different locations. Second highest rate of infestation (32%) was recorded in Bashudebpur followed by Dinajpur (31%), Pabna and Akandabaria farm (30%). The lower infestation was recorded in Kaliganj. The percentage of stems attacked at the Kaliganj has never exceeded 23% followed by Rajshahi (28%), Thakurgaon and Faridpur (29%). The rate of infestation of stem borer (Chilo tumidicostalis) in different locations varied from 23-36%. While morphological characteristics of stem borer species were identified with standard keys and species composition was only predominated by Chilo tumidicostalis Hampson, though previous workers found other borers in addition to this species. The sex ratio of adult moth Chilo tumidicostalis was 1:1.42 after emergence from the reared collected pupae from different locations. DOI: http://dx.doi.org/10.3329/sja.v11i2.18406 SAARC J. Agri., 11(2): 103-116 (2013)

(Z)–11–hexadecenyl acetate and (Z)–13–octadecenyl acetate improve the attractiveness of the standard sex pheromone of the yellow rice stem borer Scirpophaga incertulas (Lepidoptera: Pyralidae) in northern Vietnam

In a review of the pests and diseases of rice in Vietnam from 1975 onwards, Van Dinh and Doanh (2010) reported 17 key pests of rice. The most important in terms of crop areas damaged were the brown plant hopper Nilaparvata lugens (Stal), the vector of the ragged stunt and grassed stunt viruses, the rice leaf folder Cnaphalocrosis medinalis (Guenee), and the yellow rice stem borer Scirpophaga incertulas (Walker). Among four stem borer species in the Red River Delta, S. incertulas, Chilo suppressalis (Walker), Chilotraea auricilia (Dudgeon) and Sesamia inferens (Walker), S. incertulas was the dominant species, accounting for over 90% of all stem borer populations (Ho et al., 2013). However, during 2010 and 2011, the incidence of S. incertulas at Haiphong Province, a coastal area of Northern Vietnam, was very low (Ho et al., 2013). In northern Vietnam where two rice crops are grown per annum, S. incertulas has six generations per year, two on the first crop and four on the second. C. medinalis has eight overlapping generations per year, seven generations being on rice with one generation on wild grasses. There are two main rice production deltas in Vietnam, i.e., the Red River Delta and the Mekong River Delta, damage caused by S. incertulas being greatest in the former. Large areas of rice are mono–cropped in the deltas. In the Red River Delta the rice fields are sub–divided into numerous small contiguous plots (typically 20–50 plots per ha) each managed by a different farmer. In The Mekong River Delta plots are typically 1–10 ha. In both deltas farmers mainly act independently, and, as a result, the application of control measures is generally uncoordinated, resulting in comparatively poor control of these important pests. Currently, S. incertulas and C. medinalis are controlled with insecticides, one to two spray applications being made on average per crop against each pest, and a wide range of insecticides is used. Sprays to small plots are typically applied with hand lances using knapsack sprayers by individual farmers. The standard of insecticide control is variable and often poor, allowing high populations of the pest in localities to act as a source of infestation for adjacent areas where the pest has previously been well controlled. Better area–wide control tactics for the pests would be beneficial. The female sex pheromone of S. incertulas was originally identified from populations from The Philippines as a 1:3 blend of (Z)–9 hexadecenal and (Z)–11–hexadecenal (Cork et al., 1985). Cork et al. (1985) also found (Z)–11– hexadecen–1–ol and hexadecanal to be produced by females but the former compound reduced catches of (Z)–11–hexadecenyl acetate and (Z)–13–octadecenyl acetate improve the attractiveness of the standard sex pheromone of the yellow rice stem borer Scirpophaga incertulas (Lepidoptera: Pyralidae) in northern Vietnam

African Journal of Food Science and Technology

This study aimed at determining the magnitude of damage inflicted by stem borer species to Zea mays L. and Sorghum bicolor L. and refugia graminae. It involved two growing gramineous crops: maize Z.mays L. and S.bicolor L. and three gramineous forages: Napier grass, Sudan grass and giant Setaria grass. These were planted both in pure and mixed stands and exposed to natural infestation in the field.Sampling for the borer infestation was done throughout the phenology of crops .Field and laboratory bioassays were conducted to determine biophysical efficacies of the control strategy from stem borer fecunditie.The type of the gramineous refugia had a significant (p < 0.05) effect to the magnitude of damage caused by the stem borers. The B. fusca was the most devastating species with a mean of 4.8800, 3.8800, 2.2400 and 1.4000 borers while S. calamistis was the devastating with a mean of 1.0600, 0.9200, 0.4600 and 0.6100 borers in maize, sorghum, Napier and Sudan grass. However C. partellus was the most devastating species in giant Setaria grass with a mean of 3.300 and B.fusca being the least devastating with a mean of 0.6800 borer. Maize was the most damaged host indicating that it provided the best geographical requisites and nutritional attributes. These were more attractive to B. fusca.This implies that it has desirable traits attractive to the stem borers especially the great devastating B. fusca as chemical and biophysical morphology and stem diameter. B.fusca was the most devastating both in the laboratory bioassays and field. Maize was the most damaged host and Napier grass was the most preferred forage refugia. B.fusca was the devastating stem borer species and it preferred hosts with larger stems..However, more research should be conducted to understand the moths better:their biology,seasonality dynamics and generations in different locations and natural enemies surviving on maize and sorghum for their biocontrol.

English

An assessment was done during the long and short rainy cropping seasons of 2010/2011 across different agro-climatic zones (ACZs) with the objective of determining the distribution, species composition and damage levels of important stem borer species in North-eastern Ethiopia. Data were collected from 21 localities of six districts, four fields in each locality, and a total of 84 fields were assessed. Busseola fusca composed of 16 to 100% of the population of stem borer species and caused damage levels of 3 to 60% in South Wollo zone at the elevation ranging from 1750 to 2338 m. Moreover, Chilo partellus is composed of 7 to 100% of the population of stem borer species and cause a damage of 1 to 100% in the same zone at the elevation range of 1492 to 2084 m. Similarly, in North Wollo zone, B. fusca shared 69 to 88% of the total population of stem borer species and cause damage levels of 5 to 53% of the elevation ranging from 1850 to 2044 m, while C. partellus composed of 12 to 31% and caused damage of 2 to 26%. In the Oromia administrative zone, which falls at the elevation of 1400 to 1669 m, 100% of the stem borer population was C. partellus and caused a damage level of 84 to 99%. The result indicates that C. partellus widened its distribution and extent of damage from the previous report of 1900 up to 2044 m. The two stem borers were found in elevation ranging from 1750 to 2044 m but their level of distribution, compositions and damage varied between elevations. Conclusively, C. partellus widened its distribution and might have replaced the indigenous species, because it was recorded as up to 2044 m, which was not reported in the previous decades. &nbsp; Key words: Stemborers, elevation, agro-ecology, composition.

Description of a new species of coffee stem and root borer of the genus Plagiohammus Dillon and Dillon from Colombia (Coleoptera: Cerambycidae: Lamiinae), with a key to the Neotropical species

Description of a new species of coffee stem and root borer of the genus Plagiohammus Dillon and Dillon from Colombia (Coleoptera: Cerambycidae: Lamiinae), with a key to the Neotropical species

Species diversity and distribution of lepidopteran stem borers in South Africa and Mozambique

AbstractCountry‐wide surveys of lepidopteran stem borers in wild host plants were undertaken between 2006 and 2009 in South Africa and 2005 and 2010 in Mozambique. A total of 4438 larvae were collected from 65 wild host plants in South Africa and 1920 larvae from 30 wild host plants in Mozambique. In South Africa and Mozambique, 50 and 39 stem borer species were recovered, respectively, with four new species and two new genera among noctuids. Less than 5% of the total number of species collected are considered to be economically important in Africa. These species were Busseola fusca (Fuller) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae) and Sesamia calamistis Hampson (Noctuidae). Data from this study and others in East Africa on the very low abundance of stem borers in wild host plants question the putative role of wild host plants as reservoir for stem borer pests. One new host plant family (Prioniaceae), as well as 24 and 13 wild hosts from South Africa and Mozambique respectively, was added to the list of known hosts in Africa.

English

&nbsp; The quality of laboratory reared stem borer species for screening of maize varieties is usually&nbsp; questioned by end user cereal breeders. A quality check study was performed in a screen house at&nbsp; KARI-Katumani to evaluate the quality of eight-year old laboratory reared stem borer, Chilo partellus&nbsp; (Swinhoe). The evaluation was aimed at finding out the performance of the laboratory borers subjected&nbsp; to six-month interval of gene infusion in comparison with wild F1 generation of the same species&nbsp; collected from the field. One hundred (100) maize seedlings were grown on plastic pots of 5 by 5 cm and&nbsp; of 12 cm-height. The maize seedlings were infested with five first instar larvae on eight plants replicated&nbsp; four times for each borer ecotype. The wild ecotypes were collected from two different localities for&nbsp; comparison with eight-year old laboratory reared borers. Foliar damage, tunnel length on the maize&nbsp; stems and the recovered number of C. partellus larvae from the maize plants were used as the&nbsp; parameters for quality measure of the borer ecotypes. The laboratory-reared stem borer species had&nbsp; been subjected to frequent six-month gene-infusion interval from the wild. The results indicated feedvoracity drop of 3.8 and 21.5% for stem and foliar damage on the laboratory borer ecotype. The study&nbsp; established the need for continuous gene infusion to maintain high quality maize stem borer species as&nbsp; test organisms.&nbsp; &nbsp; Key words: Chilo partellus, quality insects, insect rearing, maize genotypes.&nbsp;

Maize stemborers distribution, their natural enemies and farmers’ perception on climate change and stemborers in southern Togo

Objective: The objectives of this study were to (i) assess the importance of the different stemborer species and their associated natural enemies on maize, and (ii) evaluate cereal producers’ perception on the effect of the current climate variability, on the maize stem and ear borers and their mitigation strategies to alleviate the impact of climate change on their cropping system. Methodology and results: Surveys were conducted in 2012 during the long cropping season lasting from March to July and the short one from September to October in southern Togo, to determine geographic distribution, relative importance of lepidopterous stemborers and their parasitism by natural enemies on maize. A questionnaire was introduced to evaluate cereal farmers’ perception of climate change and its effects on maize stem and ear borers. Of the total borer species recovered, the most abundant was Sesamia calamistis Hampson (Lepidoptera: Noctuidae) (76.02%), followed by Busseola fusca Füller (Lepidoptera: Noctuidae) (21.71%) and then Eldana saccharina Walker (Lepidoptera: Pyralidae) (2.27%). The borers’ abundance was affected by the agroecological zones and cropping seasons. Eldana saccharina was found in Zio and Yoto in coastal zone whereas B. fusca was recorded only in Yoto. Sesamia calamistis was the only species found in all the surveyed agroecological zones (III, IV and V). Fields were infested by all borer species at 34.4% and 83.3% in the long and short cropping seasons respectively. The percentage of infested plants ranged from 0 to 72% in the first cropping season, and 33 to 95% in the second cropping season. The borer densities varied from 0 to 3 larvae per plant in the long cropping season and 1 to 8 larvae per plant in the short cropping season. The egg parasitoid Telenomus busseolae Gahan (Hymenoptera: Scelionidae) was identified as the most important with a high natural parasitism rate of 82% on S. calamistis. The main larval parasitoid recorded was Sturmiopsis parasitica Curan (Diptera: Tachnidae) with mean parasitism ranged of between 0 and 8%. Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) infection rate vary from 0 to 5%.of borers’ larvae. Data on farmer’s perception showed that all producers recognized stem and ear borers and their damages. However, they perceive climate change effects differently by high temperatures, rains irregularity, floods, strong winds and to a lesser extent the proliferation of new pests such as termites (Isoptera), Zonocerus variegatus (L) (Orthoptera: Pyrgomorphidae) and Cicadulina spp. (Hemiptera: Cicadellidae). Adaptation strategies practiced by farmers are the choice of early maturing crop varieties, the spacing of sowing period and the crop diversification. Conclusion and application of funding: From these results, we conclude that S. calamistis, E. saccharina, and B. fusca and their associated natural enemies are present in all agroecological zones of southern Togo. These findings could serve as baseline data for further studies. Key words: Climate change, ear borers, incidence, maize, parasitism, severity, stem borers.

KEANEKARAGAMAN, DOMINASI, PERSEBARAN SPESIES PENGGEREK BATANG PADI DAN SERANGANNYA PADA BERBAGAI TIPOLOGI LAHAN DI PROVINSI JAMBI

Diversity, domination, and distribution of rice stem borer species and its damage in various land typologies in Jambi Province. The research was conducted to analyze the diversity, domination, species distribution of rice stem borers (RSB) and its damage on various land typologies in Jambi Province. The research was carried out using survey method, from December 2010 until June 2011. Samples of RSB were collected from tidal swamp in Tanjung Jabung Timur District, swampy area in Muaro Jambi District, rainfed lowland in Sarolangun District, irrigated lowland in Merangin District, and irrigated upland in Kerinci District and Sungai Penuh District. The results showed that there were five spesies of RSB found in Jambi Province. Scirpophaga incertulas Walker (yellow stem borer) was the most dominant of RSB, followed by Sesamia inferens Walker (pink stem borer), Chilo suppressalis Walker (striped stem borer), Chilo polychrysus Meyrick (dark-headed stem borer), and Scirpophaga innotata Walker (white stem borer). The distribution of S. incertulas, S. inferens, C. suppressalis and C. polychrysus were in all of rice field in Jambi Province, but that of S. innotata was limited over tidal swamp and rainfield lowland area. The RSB damage rate was lower than economic thereshold.

Composition of stem borer communities in selected vegetation mosaics in Kenya

Busseola fusca (Fuller), Sesamia calamistis Hampson, Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) are important stem borer pests of maize and sorghum in East Africa. Persistence of these pests in crop fields is blamed on the influx of diaspore populations from the neighbouring natural habitats. In addition to pest species, natural habitats support numerous non-economic stem borer species, some not known to science. However, due to growing human populations and accompanying global change, some of the natural habitats are undergoing rapid changes, a process that may result in the evolution of “new” pest species. In this study, we investigated stem borer species diversity in four different vegetation mosaics in Kenya, with an aim of establishing the differences in species composition and distributions in both wild and cultivated habitats. We identified 33 stem borer species belonging to 14 different genera in the four families; Noctuidae, Crambidae, Pyralidae and Tortricidae from 37 plant species. In addition to the above stem borer pest species, we found three more species, Busseola segeta Bowden, Pirateolea piscator Fletcher and Eldana saccharina Walker, in the cultivated fields. Together, stem borer pests varied in distribution among vegetation mosaics, suggesting differences in ecological requirement. Despite the variations in distribution patterns, stem borer pests co-existed with non-economic species in the natural habitats, communities that are facing threats due to ongoing habitat changes. This paper discusses the likely impacts of habitat changes on both pest and non-economic species.

Distribution and extent of Cotesia Flavipes Cameron (Hymenoptera: Braconidae) Parasitism in Northeastern Ethiopia.

The distribution and extent of parasitism of Cotesia flavipes Cameron (Hymenoptera: Braconidae) on stem borer species attacking maize and sorghum were assessed in three zones of northeastern Ethiopia. Cotesia flavipes was found to be the key larval parasitoid of cereal stem borer species in all areas surveyed. This parasitoid has been introduced into several African countries for the control of Chilo partellus in maize and sorghum, but it has never been released in Ethiopia. The survey results indicated that the distribution and extent of parasitism of Cot. flavipes followed the distribution and severity of its suitable host, C. partellus. A Cotesia flavipes parasitism rate of between 33% and 82% was recorded in sub-moist warm (lowland) AEZs of all zones. In contrast, a parasitism rate of less than 6% was recorded in moist, cool highland areas where Busseola fusca was the predominant species. Cotesia flavipes caused lower rate of parasitism on stem borers in maize (up to 72%) than that of sorghum (up to 82%) in the three zones. In summary, high rates of parasitism of Cot. flavipes were recorded in lowland areas where C. partellus was the dominant borer species and low rates of parasitism were recorded in highland areas where B. fusca was the predominant species. Cotesia flavipes caused the highest parasitism (82%) on C. partellus. This result verified that Cot. flavipes contributed to the reduction of C. partellus population in lowlands, regardless of the zone, and its rate of parasitism varied between crop stages, crop types, elevations, host, and host stages. Findings of this study have particularly relevant information on the contribution of Cot. flavipes to the population reduction of stem borers, time or stage of its occurrence in relation to host stages and crop stages, and its distribution in relation to the availability of a suitable host across each zone. In conclusion, this larval parasitoid plays an important role in reducing stem borer populations and can be used as one component of integrated stem borer management in northeastern Ethiopia.