Host Acceptance and Parasitoid Size as Predictors of Parasitoid Quality for Mass-Reared Trichogramma minutum

Parasitoid size and host acceptance were examined as quality control parameters for Trichogramma minutum Riley (TM) reared on a factitious host, the Mediterranean flour moth, Ephestia kuehniella Zell. (MFM), and on their target host, the spruce budworm, Choristoneura fumiferana (Clemens) (SBW). Wing length was a better predictor of potential fecundity of TM reared on SBW and MFM than hind-tibial length. SBW-reared TM were larger and had higher potential fecundities than MFM-reared TM. When given MFM eggs, SBW-reared TM did not realize their potential fecundity whereas MFM-reared parasitoids realized their potential fecundity as would have been predicted based on their body size. When given SBW eggs, both SBW-reared TM and MFM-reared TM realized their potential fecundity as predicted by their body size. When attacking SBW eggs in the laboratory, parasitoid size is a good predictor of realized fecundity for both MFM-reared and SBW-reared TM. The mean proportion of time spent on the egg mass during a 2-h host acceptance assay was a good predictor of the mean-realized lifetime fecundity of TM attacking SBW eggs. Lab assays that predict field performance of mass-released parasitoids will allow for the modification of release rates in response to measured reductions in parasitoid quality in the rearing facility. Increasing release rates may, in many cases, be an adequate and probably easier adjustment than modifying mass-production techniques to account for fluctuations in quality of rearing stock.