Performance and functional responses of the thelytokous and arrhenotokous strains of Neochrysocharis formosa to Tuta absoluta, a globally severe tomato pest

The native thelytokous (TH) and arrhenotokous (AR) strains of Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) are promising biocontrol agents against the invasive tomato pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). This study assessed the performance and preferences of these strains in choice experiments involving five host instar ratios and evaluated their functional responses to seven densities of 1st instar larvae (5 to 40 hosts). In host-attacking behavior assays, an increasing proportion of 1st instar larvae led to a significant rise in host mortality rates for both strains. Both strains exhibited strong preferences for parasitizing and attacking 1st instar larvae over later instars, with the TH strain demonstrating significantly greater host-killing efficacy than the AR strain. Functional response experiments revealed that the attack rates of both strains were positively correlated with host density. Parasitism by both strains and host-stinging behavior by the TH strain showed type III functional responses, while host-feeding by both strains and host-stinging by the AR strain followed type II functional responses. Early establishment of the TH strain in tomato agroecosystems could enhance the management of T. absoluta. These findings provide critical insights into the functional dynamics of the TH and AR strains of N. formosa that can inform the development of effective biocontrol programs for this globally significant pest.