Novel source of sorghum tolerance to the African stem borer, Busseola fusca

The stem borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is an important pest of maize and sorghum in sub-Saharan Africa. This insect has oligophagous feeding habits, feeding mostly on maize and sorghum with a narrow range of wild Poaceous plant species. We hypothesised that first instar B. fusca larvae, the critical stage for successful establishment on a host plant, can establish and then grow on a particular plant as a result of induction of a complement of digestive enzymes that mediates host acceptance at first instars. A fast semi-quantitative analysis of potentially digestive enzymatic activities present in the first larvae previously fed for 4 days on leaves of host and non-host plants was performed using the API-ZYM kit system able to detect a multiplex of enzyme activities. Regardless of the plant species, the larvae exhibited higher activities of the carbohydrate metabolising enzymes than of aminopeptidases and proteases. In addition, highest activities of carbohydrates degrading enzymes were exhibited by larvae that consumed leaves of the most preferred plant species of B. fusca. Conversely, esterases were only detected in neonate larvae that consumed leaves of the less preferred and non-host plants. No alkaline phosphatase and lipase activities were detected. The significance of these results was discussed in terms of food requirements of first instar larvae when settling on a plant.

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

International Journal of Insect Science ◽

10.4137/ijis.s11009 ◽

2013 ◽

Vol 5 ◽

pp. IJIS.S11009 ◽

Cited By ~ 4

Author(s):

Asmare Dejen ◽

Emana Getu ◽

Ferdu Azerefegne ◽

Amare Ayalew

Keyword(s):

Busseola Fusca ◽

Relevant Information ◽

Stem Borer ◽

Cotesia Flavipes ◽

Stem Borers ◽

Parasitism Rate ◽

African Countries ◽

Suitable Host ◽

Predominant Species ◽

Larval Parasitoid

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.

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