Predator‐parasitoid‐host interaction: biological control of Rhyzopertha dominica and Sitophilus oryzae by a combination of Xylocoris flavipes and Theocolax elegans in stored cereals

Abstract

Post‐harvest management constraints are economically significant in Africa for a broad range of commodities, resulting in a substantial negative impact on food security and livelihoods. Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) coexists with Sitophilus oryzae (L.) (Coleoptera: Dryophthoridae) – they infest stored cereal grains, especially in sub‐Saharan Africa, and cause significant losses in storage. Laboratory studies were carried out to determine the efficacy of Xylocoris flavipes (Reuter) (Hemiptera: Anthocoridae) and Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae), alone or in combination, in suppressing populations of R. dominica and S. oryzae in stored rice and wheat grains. The weight loss and moisture of the infested grains were assessed, for the various combinations of the two pest insects and the two natural enemies. In rice there was a synergistic effect of the combined release of T. elegans and X. flavipes against both R. dominica and S. oryzae compared to the effect of one natural enemy alone. With the combined release, only 2% F1 progeny of the pest beetles emerged compared to the untreated control (100%), whereas 3.5 and 6% emerged when X. flavipes and T. elegans, respectively, were released alone. When the two natural enemies were released in combination, 0.4% R. dominica F1 progeny emerged, compared to 1.6% with X. flavipes or T. elegans alone. In the combined release only 0.3% S. oryzae F1 progeny emerged, whereas 65% emerged with X. flavipes alone and 41% with T. elegans alone. No synergistic effect of the combined release of the two natural enemies was detected in wheat. In stored rice, the lowest percentage of weight loss (44%) was found when both natural enemies and both beetle species were present. We conclude that the combination of the predator and the parasitoid should be recommended when R. domininca and S. oryzae coexist and feed on stored cereals, especially rice.

Genome assembly of the ectoparasitoid wasp Theocolax elegans

“…The ectoparasitoid wasp Theocolax elegans (Westwood) is a cosmopolitan and generalist pteromalid parasitoid of many major storage insect pests 11 . Augmentative releases of T. elegans can effectively diminish more than 90% of the Rhyzopertha dominica population in stored wheat as well as insect fragments in wheat flour 12 , 13 .…”

Modulation of Aleurone Peroxidases in Kernels of Insect-Resistant Maize (Zea mays L.; Pob84-C3R) After Mechanical and Insect Damage

“…Previous research has identified saliva components from S. zeamais that induced the production of synomones in rice and wheat grains, which triggered an indirect defensive response by attracting females of the ectoparasitoid Theocolax elegans (Tang, 2016). This parasitoid has been suggested as a potential biocontrol agent for diverse Coleoptera that develops inside cereal grains or legume seeds, including S. zeamais (Dlamini and Amornsak, 2014;Adarkwah et al, 2019). Endosperm PODs and phenolic compounds have also been established as biochemical resistance factors (Arnason et al, 1992;Sen et al, 1994;García-Lara et al, 2007;López-Castillo et al, 2018b) that reinforce cell walls and improve pericarp thickness and toughness (Saulnier and Thibault, 1999;García-Lara et al, 2004).…”

Chemical vs. Enzymatic Refining to Produce Peanut Oil for Edible Use or to Obtain a Sustainable and Cost-Effective Protector for Stored Grains against Sitophilus zeamais (Coleoptera: Curculionidae)

“…Such insects already consume and damage up to 20% of the yielded grains, and the percentage is supposed to increase due to the rising temperatures [20,21]. Their management has been lately attempted using eco-friendly substances such as inert dusts [22][23][24] and essential oils [25][26][27][28] and employing predators and parasitoids [29,30]. Despite this, phosphine and synthetic insecticides are still widely applied [31,32], and these chemical solutions cause resistance development even in field populations, with severe drawbacks for the environment and non-target species [33,34].…”