Development and yields of the tachinid Exorista larvarum in three common Noctuidae of Azores Archipelago and in a laboratory host

The development of the tachinid larval parasitoid Exorista larvarum (L.) was studied upon Peridroma saucia (Hübner), Pseudaletia unipuncta (Haworth) and Xestia c-nigrum (L.) (Lepidoptera Noctuidae), all of them being common pests of pastures and horticultural crops in the Azores Archipelago, and in the laboratory host Galleria mellonella L. The study occurred under laboratory conditions, but relied on noctuids samples collected on Terceira island. The experiments were conducted at 15, 20 and 25 °C to determine the effect of temperatures commonly recorded in the Azores throughout the year on the tachinid development. All host species were accepted by E. larvarum females, but more eggs were laid on the noctuids than on G. mellonella both at 20 and 25 °C. The effect of temperature on the number of eggs laid was significant only for G. mellonella and X. c-nigrum, although on all species fewer eggs were laid at 15 °C (the mean winter temperature in the Azores). At 15 °C, no puparia were obtained from any host species. At 20 °C no puparia formed in G. mellonella and parasitoid pupation percentages were extremely low also in the noctuids. At 25 °C the puparial yields obtained in the latter were considerably lower than those found in G. mellonella (=13%). In all moth species, including noctuids, host larval mortality was however very high despite the low percentages of puparia obtained. The efficiency of E. larvarum as a biocontrol agent could be enhanced by host mortality due to incomplete parasitoid development.