Background: There is a consensus that the conservation of natural enemies is the most important biological control strategy, but it has also been the least attended. The reason is simple: there is a strong contradiction between modern agriculture and biological control. Various strategies have been proposed for the conservation of natural enemies, among others, protection against pesticides and establishment of nectar plants as alternative food. Less attention has been paid to the conservation of alternative hosts for natural enemies. Main body: Natural enemies are not exclusive to pests, on the contrary, numerous species require alternative prey and hosts for their prevalence. Their conservation is a strategy widely referenced in scientific literature; however, this idea is not consistent with the studies developed. From 1973 to 2021, only 21 studies that emphasized the use of alternative hosts were recorded. Most focused on single phytophagous–natural enemy species, and little attention was given to the plant–phytophagous relationship. For example, Asclepias curassavica (Apocynaceae) hosts more than nine species of specialist phytophagous; and they, in turn, attracted 24 species of natural enemies. Although different studies demonstrate the potential of alternative hosts, some presume an adverse or doubtful effect on pest control; for example, additional vegetation in agroecosystems could act as a source, but also as a sink for natural enemies. This analysis tries to fit biological control to the modern agricultural paradigm, and not the other way around, as suggested by ecological theory. We support the idea that conservation biological control should be directed toward the conservation of multiple species, with the aim of controlling not only pest, but also the self-regulation of the agroecosystem. The path that should be followed by the study and application of alternative hosts as a strategy of biological control by conservation is discussed. Conclusion: The wide diversity of non-pest insect species suggests an enormous potential for their exploitation as alternative hosts. The evaluation of host plants of specialized phytophagous species could improve biological control and reduce the risk of pests for crops. This strategy would partly fill the huge gap that exists in modern agroecosystems in terms of biological diversity.

To understand the entomofauna and potential as alternate hosts for natural enemies of Asclepias curassavica L., a study was established between 2012 and 2013 at Emiliano Zapata, Villamar, Michoacan, Mexico. Fifty plants of A. curassavica were planted in pots, and phytophagous arthropods, predators, parasitoids, and aphid parasitism were sampled and recorded each week. Ten species of phytophagous arthropods were identified, including Aphis nerii B. de F., Danaus plexippus L, Oncopeltus fasciatus Dallas, Lygaeus reclivatus Say, and Liriomyza asclepiadis Spencer. Seven species of parasitoids and 14 predators were recorded. Trichogramma pretiosum Riley was an important parasitoid in eggs of D. plexippus, while Lysiphlebus testaceipes (Cresson) was the most important parasitoid in A. nerii. The most important predators were Pseudodorus clavatus (Fabricius), Leucopis sp. (both 14.97%), Chrysopidae (21.43%), and Coccinellidae families; Cicloneda sanguinea L. (55.22%) and Scymnus sp. (3.84%) were the mo... Resumen. Para conocer la entomofauna asociada a Asclepias curasavica L. y su potencial como hospederos alternos de enemigos naturales, durante 2012–2013 se estableció un estudio en Emiliano Zapata, Villamar, Michoacan, Mexico. Plantas de A. curassavica se establecieron en macetas (50) y semanalmente se registraron artropodos fitófagos, depredadores, parasitoides y parasitismo en áfidos. Se identificaron 10 especies de artrópodos fitófagos, entre ellos, Aphis nerii B. de F., Danaus plexippus L., Oncopeltus fasciatus Dallas, Lygaeus reclivatus Say, y Liriomyza asclepiadis Spencer. Trichogramma pretiosum Riley fue un importante parasitoide en huevos de D. plexippus, mientras Lysiphlebus testaceipes (Cresson) fue el mas importante parasitoide en A. nerii. Los más importantes depredadores fueron Pseudodorus clavatus (Fabricius), Leucopis sp. (Ambos 14.97%), las familias Chrysopidae (21.43%), y Coccinellidae; Cicloneda sanguinea L. (55.22%) y Scymnus sp. (3.84%) fueron las especies mas importantes. Holobus sp. ...

We evaluated the pathogenicity of the entomopathogenic nematodes native to Mexico, Heterorhabditis indica, Heterorhabditis sp. and Steinernema sp., towards M. domestica under controlled conditions. For adults, concentrations of 1,600 (A) and 1,200 (B) nematodes/ml were considered. For larvae, only the first concentration applied to filter paper, wheat bran, and peat moss as substrates was evaluated. An analysis of variance showed that the differences in adult mortality were only significant (p = 0.0001) among nematode species but not among concentrations within species. However, differences were significant (p = 0.0001) when data were analyzed when 50% of the individuals died (LT₅₀). For H. indica, the LT₅₀ were 46.5 h and 65.8 h for the concentrations A and B, respectively. Females were more susceptible than males. H. indica recorded the highest mortality, with 79.2% and 35.5% for females and males, respectively. Significant differences (p ≤ 0.05) were recorded in larval mortality. H. indica induced the highest mortality (53.3%) when applied on peat moss. The results are a fundamental basis for future management studies of M. domestica by entomopathogenic nematodes.

Background: Oebalus mexicanaSailer (Hemiptera: Pentatomidae) is an important pest of sorghum in Central-Western Mexico. In addition to damaging the grain, it is a vector of the panicle blight,Fusarium moniliforme.Oebalus mexicanahibernates at > 2200 m above sea level (masl), and its control in these sites is through entomopathogenic fungi (EPF). Their effectiveness could be misperceived as natural epizootics at hibernation sites. To characterize fungal epizootics associated with hibernating adults ofO. mexicana, during 2019 and part of 2020, a study was established in the Zináparo hill, Michoacan, Mexico. Three sampling strata were defined—two at low (2219 masl) and high levels of elevation (2351 masl), and another one at intermediate elevation (2244 masl) and soil humidity most of the year. Under the leaf litter, live arthropods and corpses with and without mycosis were recorded every 2 weeks; associated EPF were isolated and identified. Soil humidity, temperature, and RH under the litter were recorded.Results: Six genera of fungi were identified, withBeauveriabeing the most prevalent. Mortality ofO. mexicanain the field was > 80%, with a high correlation (r = 0.85–0.97) with mortality due to fungi (> 65%). The humidity of soil and litter created a suitable environment for the development of epizootics. The highest prevalence was registered at the elevations of 2244, 2351, and 2219 masl, respectively. More than 15 families of arthropods were registered, several of them with the presence of mycosis. Their permanence as alternate hosts contributed to the persistence of the fungi. Field and laboratory evidences suggested that the frequent flights ofO. mexicanafavoured the self-dissemination of EPF. Thus, more than 37% of live individuals with inoculum and subsequent infection and death were recorded.Conclusions: The EPF disease at overwintering sites ofO. mexicanawas enzootic, and under favourable conditions it can become epizootic. The high levels of natural control in hibernation sites suggest that additional control measures forO. mexicanaare unnecessary; on the contrary, the conservation of these sites as reservoirs of EPF is proposed for a sustainable use in the management of this and other pests.