There was a typo in the fifth author's name in the initial online publication. The original article has been corrected.

Exotic invasive insect herbivores have the potential to interfere with existing herbivore-natural enemy interactions in new environments. Fall armyworm (FAW), Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a new invasive pest in maize fields in Africa. Understanding the acceptability and suitability of FAW to existing maize stemborer-parasitoid interactions is the first step in elucidating the impact that this exotic insect pest can have on the existing natural enemies used in biological control of maize stemborers in Kenya. The most commonly used larval parasitoids for biological control programs against maize stemborer communities in East Africa are Cotesia flavipes Cameron (Hymenoptera: Braconidae) and two populations of the native Cotesia sesamiae (Cs-Inland and Cs-Coast) Cameron (Hymenoptera: Braconidae). All these parasitoid species attacked FAW larvae but none yielded offspring, although they induced high non-reproductive host mortality when compared to natural mortality. Furthermore, the parasitoids that inserted their ovipositor into FAW larvae exhibited no significant preference between FAW larvae and their respective stemborer hosts under dual-choice bioassays. In olfactometer bioassays, the parasitoids were more attracted to plants infested by FAW than uninfested plants and even showed a marked preference for the odours of plants infested by FAW over those of plants infested by their natural host counterparts. This study illustrates that exotic pests, such as FAW, can impact existing stemborer-parasitoid interactions associated with maize, even if they cannot be used as hosts by parasitoids associated with these stemborers. Although additional studies are needed, FAW might therefore have a negative impact on stemborer biological control existing before its invasion.

The application value of Pseudomonas protegens in agriculture has been widely studied, but the manufacturing processes used to produce P. protegens limits its usefulness as a biological control agent because of its poor shelf life due to low stress resistance during processing. We combined hyperosmotic cultivation and fluidized-bed drying to prepare much more stable P. protegens preparations. During drying and cryogenic storage, the viability of hyperosmotic cells was significantly improved compared to that of cells prepared by previous methods. Addition of skim milk provided an excellent protective effect for both hyperosmotic and standard cells. In two field trials, when the concentration of the P. protegens preparation was 0.333% w/v, the biocontrol efficacy against tomato bacterial wilt was more than 80%, which was significantly higher than that of the control provided by the antibiotics zhongshengmycin and streptomycin sulfate. The results show that P. protegens products can be successfully prepared by combination of hyperosmotic cultivation and fluidized-bed drying.

The Enemy Release Hypothesis (ERH) has been a factor influencing the establishment of some exotic species worldwide. We tested if the ERH could be influencing populations of the exotic predator Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Brazil. During two years, three local predatory coccinellid species and Harmonia axyridis were sampled in Brassica oleracea in six organic farms in the midwest of the country. Parasitoids were detected by rearing (emerged) and qPCR Melting Curve Analysis (unemerged). Host density-dependence and spillovers were used to evaluate coccinellid population effects of parasitism. Six parasitoid species were found, including two new records for Brazil. Although Harmonia axyridis harbored fewer parasitoid species, parasitism was not lower and parasitoid density-dependence was not weaker on it compared to the local species. Spillovers among hosts occurred both onto Harmonia axyridis and from it. The ERH was rejected for these parasitoids and, therefore, it did not contribute to the invasiveness of Harmonia axyridis in Brazil.

Generalists rarely are considered for classical biocontrol because their broad feeding habits are expected to make non-target impacts inevitable. This assumes an increase in overall ecological risk with increasing number of feeding connections. With the goal of inspiring fresh consideration of the safety of exotic biocontrol agents for classical biocontrol, we present a selective review of the impacts of nine particularly-well-studied exotic natural enemies ranging from relative specialists to generalists. Surprisingly, non-target effects could be particularly strong for relative specialists that attacked just a few natives, but were often widespread but weak for the broadest generalists. This appeared to reflect relatively strong apparent competition and density-dependence for the narrow feeders, versus broadly diffuse net effects for the broader feeders. Overall, we suggest a sole focus on specialists in classical biocontrol might be an unreliable means to reduce ecological risk. Additional research is needed to fully compare the net direct and indirect effects of generalists and specialists across food webs, following classical biocontrol releases.

Cerambycid and buprestid woodborers are important invasive forest pests. Parasitoids play a unique role in reducing woodborer populations because of their specific adaptations regarding host concealment. We reviewed parasitoid guilds of cerambycid and buprestid woodborers to characterize their life-history traits and macroecological patterns of host use. The parasitoid guilds shift from more specialist endoparasitoids to more generalist ectoparasitoids following the hosts’ ontogeny and the increased concealment of host feeding niche. Larval ectoparasitoids dominate the guilds, and many of them locate hosts through substrate vibration from living hosts, rendering attacked (paralyzed) hosts undetectable by other parasitoids and consequently leading to a rarity of multiparasitism. These characteristics promote novel associations between exotic woodborers and extant larval parasitoids, leading to coexistence and synergistic regulation of host populations by different parasitoids. We provide case studies to propose a framework of optimal use of co-evolved and novel associations for complementary suppression of invasive woodborer populations. We also discuss potential non-target impacts for the use of generalist parasitoids in biological control of invasive cerambycid and buprestid woodborers.

Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) is an important primary parasitoid of Bactericera cockerelli (Sulc) (Hemiptera: Triozidae). This study aimed to unveil the parasitoid’s circadian rhythms and provide information for enhancement of its biological control. Most emergence occurred in the morning and most mating took place early next morning. Oviposition only occurred during the daytime, peaking between mid-morning and mid-afternoon while host feeding had three peaks in the early morning, late afternoon and dawn, respectively. We demonstrate that circadian activity peaks for different life functions did not overlap, suggesting that T. triozae have developed strategies for maximal fitness gain. These findings have implications in pest management, which can be tested under field conditions. For example, release of sexually mature and host-fed adults in the early morning may help achieve better control. Moreover, insecticide sprays, when necessary, may be applied as late in the evening as possible to reduce side effects on this parasitoid.

In hymenopteran parasitoids, isolated geographic populations can show morphological variation and reproductive incompatibility that may lead to failures in biological control programs when they are intended to be used as biocontrol agents. Through a classical morphometric approach we confirm the specific identity of three local populations of the larval arrhenotokous endoparasitoid Pseudapanteles dignus (Muesebeck) (Hymenoptera: Braconidae) of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), from three main tomato producing areas of Argentina. Moreover, we examined reproductive compatibility by outcrossing the three populations. Morphometric differences among P. dignus biotypes were found but no evidences of mating incompatibility among them existed. This laboratory study contributes with relevant information to the original description of the species P. dignus and has significant implications for T. absoluta biological control using this parasitoid in tomato crops from different regions of Argentina.

The aim of our study was to determine the usefulness of mixtures of carvacrol and Bacillus thuringiensis crystalline proteins Cry against pests of two different species: Cydia pomonella L. (Lepidoptera: Tortricidae) and Spodoptera exigua Hübner (Lepidoptera: Noctuidae). The novelty of our work lies in showing the interactions between carvacrol and bacterial toxins against insect pests. Moreover, we have demonstrated that carvacrol applied via ingestion exerts toxicity against lepidopteran caterpillars. We have shown that the botanical compound and Cry proteins act in synergy and their mixtures are most effective in reducing the number of L1 and L3 larvae when B. thuringiensis toxins constitute up to 0.1% and 0.05% of the mixtures, respectively. Carvacrol and crystalline proteins act in synergy in these combinations and have the potential to be effective in protecting crops against lepidopteran pests. The nature of the interaction between the components depended on the proportion of their concentrations in the mixture. Mixtures containing Cry toxin concentrations equal or higher than 20% caused lower observed mortality of insects compared to the expected one. Furthermore, we showed that crystalline proteins of B. thuringiensis MPU B9, carvacrol and their mixture did not affect the morphology of insect haemocytes, and additionally, had no effect on the immune system.

The field of plant protection is steadily reducing the use of chemicals by increasing the use of microbial biocontrol agents. At present, several microorganisms are active ingredients of the so-called biofungicides and some of these are based on yeasts. Molecular techniques applied in microbial taxonomy are leading to extensive revisions of the classification of many microbial groups, including various yeasts used for biocontrol. Recent taxonomic revision of the basidiomycete genus Cryptococcus resulted in C. laurentii (Kufferath) Skinner (Tremellales) being renamed as Papiliotrema laurentii, including strains displaying biocontrol activity, such as strain LS28. In this study, we performed comparisons of ITS, D1D2, TEF1, and RPB1 nucleotide sequences of LS28 with the corresponding genes of the type strains of taxonomically related species. We found that the yeast strain LS28 belongs to the species P. terrestris (Tremellales) (Crestani et al. Int J Syst Evol Microbiol 59:631–636, 2009) rather than P. laurentii. We encourage other groups working on biocontrol to perform molecular characterization of their yeast(s) of interest to identify the species that have the highest potential for practical applications and facilitate possible commercial registration.