Abstract
The quality of laboratory reared stem borer species for screening of maize varieties is usually questioned by end user cereal breeders. A quality check study was performed in a screen house at KARI-Katumani to evaluate the quality of eight-year old laboratory reared stem borer, Chilo partellus (Swinhoe). The evaluation was aimed at finding out the performance of the laboratory borers subjected to six-month interval of gene infusion in comparison with wild F1 generation of the same species collected from the field. One hundred (100) maize seedlings were grown on plastic pots of 5 by 5 cm and of 12 cm-height. The maize seedlings were infested with five first instar larvae on eight plants replicated four times for each borer ecotype. The wild ecotypes were collected from two different localities for comparison with eight-year old laboratory reared borers. Foliar damage, tunnel length on the maize stems and the recovered number of C. partellus larvae from the maize plants were used as the parameters for quality measure of the borer ecotypes. The laboratory-reared stem borer species had 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 established the need for continuous gene infusion to maintain high quality maize stem borer species as test organisms. Key words: Chilo partellus, quality insects, insect rearing, maize genotypes.
Highlights
The spotted stem borer Chilo partellus Swinhoe (Lepidoptera: Crambidae) and the African stem borer Busseola fusca Fuller (Lepidoptera: Noctuidae) are the most important lepidopteran stem borer species causing substantial annual loss of maize (Zea mays L.) production estimated at 13.5%, and worth US $91 millions in Kenya (DeGroote, 2002). Hassan (1998) had given an estimate of 0.4 million tons of potential yield in the country
The results indicated feedvoracity drop of 3.8 and 21.5% for stem and foliar damage on the laboratory borer ecotype
The study results show that the quality of the laboratory C. partellus borers had lower voracity of feeding on the maize plants
Summary
The spotted stem borer Chilo partellus Swinhoe (Lepidoptera: Crambidae) and the African stem borer Busseola fusca Fuller (Lepidoptera: Noctuidae) are the most important lepidopteran stem borer species causing substantial annual loss of maize (Zea mays L.) production estimated at 13.5%, and worth US $91 millions in Kenya (DeGroote, 2002). Hassan (1998) had given an estimate of 0.4 million tons of potential yield in the country. Hassan (1998) had given an estimate of 0.4 million tons of potential yield in the country. Grain maize is one of the most important food staples in sub-Saharan Africa, providing food and income to well over 300 million resource-poor smallholders (FAO, 2008). Its cultivation spans the entire continent and it is the dominant cereal food crop in many countries, accounting for 56% of total harvested area of annual food crops and 30 to 70% of total caloric consumption (FAO, 2008; World Bank, 2011). Stem borers play a considerable role in reducing maize yield in Africa through damaging the leaves, stem, ears and kernels. Various control mechanisms have been evaluated including chemical, cultural, host plant resistance, and classi-
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