Comparative Studies on the Fecundity, Egg Survival, Larval Feeding, and Development of <I>Chilo partellus</I> and <I>Chilo orichalcociliellus</I> (Lepidoptera: Crambidae) on Five Grasses

Abstract

Chilo partellus (Swinhoe) and Chilo orichalcociliellus Strand (Lepidoptera: Crambidae) are gramineous stem borers that occur sympatrically in the southern coastal area of Kenya. Evidence over a 30-yr period indicates that the indigenous stem borer, C. orichalcociliellus, is being gradually displaced by the exotic stem borer, C. partellus. Comparative laboratory studies were conducted in several large-stemmed grasses to examine factors that may be involved in the displacement of C. orichalcociliellus, and to examine other possible effects of the invasion of C. partellus into Kenya. C. partellus had a higher fecundity than C. orichalcociliellus at 25 and 28ЊC, but not at 31ЊC. In addition, more C. partellus than C. orichalcociliellus eggs survived to the Þrst instar. C. partellus larvae developed faster than C. orichalcociliellus in maize and sorghum. In this shorter developmental time, C. partellus consumed more maize than C. orichalcociliellus, but both species consumed equal amounts of sorghum. On a daily basis, C. partellus consumed more maize and sorghum than C. orichalcociliellus. A few C. orichalcociliellus survived to the pupal stage in napier and guinea grasses, whereas no C. partellus survived. The shorter developmental period of C. partellus may give this species a competitive advantage over the slower developing C. orichalcociliellus. However, the ability of C. orichalcociliellus to complete development in two native grasses in which C. partellus did not survive may provide a refuge that has allowed C. orichalcociliellus to escape extirpation from the coastal area of Kenya.

Biology and Management of Economically Important Lepidopteran Cereal Stem Borers in Africa

“…In coastal Kenya, there is evidence that C. partellus has partially displaced the indigenous stem borer, C. orichalcociliellus (130)(131)(132)141). However, C. orichalcociliellus continues to be found at a relatively high frequency (10-30% of the borer complex), which suggests that the displacement of C. orichalcociliellus will not proceed to extirpation (228).…”

“…However, C. orichalcociliellus continues to be found at a relatively high frequency (10-30% of the borer complex), which suggests that the displacement of C. orichalcociliellus will not proceed to extirpation (228). Recent investigations have found that C. orichalcociliellus completed development in two native grasses, in which C. partellus could not develop (131), which may be one factor that allows their continued coexistence.…”

“…C. partellus completes a generation in less time than C. orichalcociliellus (101,131), which may result in a higher population growth rate. Moreover, C. partellus terminates diapause more rapidly than C. orichalcociliellus (130) or B. fusca (92), which may allow C. partellus to colonize host plants before the two native species at the beginning of growing seasons.…”

Diversity of alternative hosts of maize stemborers in Trans-Nzoia district of Kenya

“…Despite a higher attractiveness of certain wild host plant species to ovipositing females, poor larval performance has been recorded in most of these plants compared to maize (Khan et al, 2000;Ofomata et al, 2000;Schulthess et al, 1997). On maize, more than 70% of the stemborer larvae pupated, while less than 30% of larvae reached the pupal stage on some wild grass species (Schulthess et al, 1997).…”

In Vitro Anti-Acetylcholinesterase Activity of Dichloromethane Leaf Extracts of Carphalea glaucescens in Chilo partellus Larvae

“…C. partellus is very invasive and once it invades an area it displaces native species and is widely distributed. In coastal Kenya, there is evidence that C. partellus has partially displaced the indigenous stem borer, Chilo orichalcociliellus [2][3][4].…”