Cotesia vanessae

Pacheco, Henry Murillo, Vanlaerhoven, Sherah & Garcia, M. Angeles Marcos, 2021, Host suitability of Trichoplusia ni and Chrysodeixis chalcites (Lepidoptera: Noctuidae) for native and nonnative parasitoids expanding their host range, The Canadian Entomologist 153 (2), pp. 137-149 : 141-143

Cotesia vanessae

Parasitoid success of C. vanessae was higher on T. ni than on C. chalcites , yet parasitoid cocoon mortality was lower on T. ni than on C. chalcites (F 1,18 = 4.703, P = 0.044; U = 13,874.00, P <0.001, respectively; Fig. 3 ). Host mortality was lower on parasitised T. ni than on parasitised C. chalcites (F 1,18 = 7.714, P = 0.012), and host success was similar between both parasitised host species (U = 48.00, P = 0.912; Fig. 3 ). Host mortality of parasitised T. ni and C. chalcites (4.10 ± 0.55 and 5.90 ± 0.35 dead larvae, respectively) by C. vanessae was higher (F 1,18 = 12.37, P = 0.002; F 1,18 = 54.76, P <0.001, respectively) than on nonparasitised hosts (1.80 ± 0.36 and 2.20 ± 0.36, respectively). The brood size of C. vanessae was higher (U = 4720.50, P <0.001) on T. ni than on C. chalcites (52.11 ± 2.11 and 30.24 ± 1.3 parasitoids, respectively).

The multinomial logistic regression indicated that the interaction of host success (Wald = 0.003; df = 1; P = 0.959) and host mortality (Wald = 3.28; df = 1; P = 0.070) with parasitoid success was similar between the parasitised larvae of host species.

The development times from oviposition to cocoon formation and oviposition to adult emergence of C. vanessae were shorter on T. ni than those on C. chalcites (U = 16 184.00, P <0.001; U = 4411.00, P <0.001, respectively; Fig. 2 ). However, the time from cocoon formation to adult emergence of the parasitoid did not differ significantly between either host species. (U = 9833.00, P = 0.573; Fig. 2 ).

Figures

Fig. 3. Suitability parameters of hosts Trichoplusia ni and Chrysodeixis chalcites parasitised by Cotesia vanessae. Parasitoid success is expressed as the number of hosts from which adult solitary or gregarious parasitoids are developed. Parasitoid cocoon mortality is expressed as the number of developed cocoons from which adult parasitoids did not emerge. The host success is measured as the number of hosts that developed into adult moths, whether the host was parasitised or not. Host mortality is calculated from the number of hosts that died after parasitism without developing into a moth or parasitoid. Sample size = 20; replicates = 10. Notes: Means (±SE) within each variable response with the same letter are not significantly different (P> 0.05) between host species. Parasitoid success and host mortality were analysed using ANOVA, and parasitoid cocoon mortality and host success were analysed using Mann–Whitney U tests for independent samples.

Fig. 2. Development times in days for Campoletis sonorensis and Cotesia vanessae on Trichoplusia ni and Chrysodeixis chalcites. White: days from oviposition to cocoon formation; light grey: days from cocoon to adult emergence; dark grey: days from oviposition to adult emergence. Means (±SE) with the same letter within each parasitoid species are not significantly different (P> 0.05). Parameters were analysed using Mann–Whitney U tests for independent samples for each parasitoid species and each parasitoid development stage separately.