Assessments of floral feeding and parasitism by Peristenus relictus (Ruthe) (Hymenoptera: Braconidae) in a diversified strawberry production system

The parasitoid Peristenus relictus was introduced to California to
reduce populations of Lygus hesperus Knight, which is a key pest
of strawberry. To improve the biocontrol provided by P. relictus,
feeding studies were conducted to determine if this parasitoid
could benefit from the floral resources provided by strawberry
with alfalfa (Medicago sativa) trap crops. Buckwheat (Fagopyrum
esculentum) was also included as a beneficial insectary candidate.
Specifically, parasitoid longevity and nutrient consumption were
assessed. Both longevity and sugar-consumption by P. relictus
females were significantly higher when exposed to a sucrose
solution than either strawberry or alfalfa flowers. Fructose
consumption by P. relictus provided with buckwheat flowers was
comparable to parasitoids given a sucrose solution and was
significantly greater than water. Buckwheat was thus trialed on
organic strawberry ranches. Buckwheat was intercropped
throughout 0.2 hectares of strawberry and compared to an
equivalent control on 4–5 ranches per year. However, the
percentage of parasitised L. hesperus nymphs collected from
strawberry intercropped with buckwheat (14.0 ± 1.9%) and
strawberry alone (12.5 ± 1.9%) was not significantly different.
Buckwheat was subsequently paired with alfalfa trap crops in
2024 in the hope that treatment effects would be more
discernable in a habitat with higher host densities. In this case,
alfalfa paired with buckwheat provided significantly higher levels
of parasitism (41.7 ± 5.0%) compared to alfalfa alone (9.0 ± 2.5%).
The compatibility of P. relictus with strawberry, alfalfa and
buckwheat flowers is discussed, along with the feasibility of
buckwheat to be utilised as a companion plant.