Evaluation of Groundnut Varietal Resistance against Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Abstract

A laboratory study was conducted to evaluate resistance of 10 groundnut varieties (Tsosabana, Peolwane, Nakwana, Sellie, GO74, GO15, GO73, BMM188, GO64-B and BMM268) against Plodia interpunctella using life table parameters of the insect and level of seed damage. Fecundity and survival, longevity, intrinsic rate increase (rm), net reproduction rate (R0), generation time (T), doubling time (Td) as well as finite rate of increase (λ) were used. The hypothesis of this study was that negative effects of groundnut varieties on life table parameters of P. interpunctella will indicate levels of resistance. Fecundity, survival and R0 varied significantly among varieties while the rest of parameters showed no significant differences. The lowest number of eggs laid and hatchability per female were significantly lower on variety BMM268. Gravid females stopped laying eggs by day 8 on Sellie and BMM268. The survival rates of P. interpunctella were lower on BMM268 and Sellie and the larvae were all dead by day 8. Plodia interpunctella had short life expectancy of 8 days when reared on varieties Sellie and BMM268 compared to other varieties. Variety BMM268 had significantly lower R0 than other varieties. Based on means, there was also a slightly prolonged larval developmental period on variety BMM268 than other varieties though not significant. Considering damage, varieties Sellie and BMM268 also had the lowest number of tunnels than others except G064-B. Susceptibility index ranged from 3.12–6.91 amongst varieties and the lowest was recorded on BMM268 followed by Sellie. This study shows that Sellie and BMM 268 are relatively unsuitable as hosts, indicating some level of resistance to P. interpunctella. The two groundnut varieties can be used in integrated pest management programmes to reduce damage caused by P. interpunctella during storage.