Eric W. Riddick

Benefits and limitations of factitious prey and artificial diets on life parameters of predatory beetles, bugs, and lacewings: a mini-review

The primary peer-reviewed literature pertaining to rearing of predatory beetles, true bugs, and lacewings was reviewed and synthesized. This study focused on the literature published from 1998 to 2007. Advances in rearing were revealed in relation to the influence of factitious prey and artificial diets on predator life parameters. Eggs of the Angoumois grain moth and Mediterranean flour moth were factitious prey that supported the development and reproduction of many species in lieu of natural prey. Artificial diets based on vertebrate protein were generally inferior to factitious prey for production of predators. A few exceptional cases demonstrated potential for continuous rearing of true bugs and lacewings on artificial diet, as a stand-alone food source. Factors that could ensure progressive rearing success might involve (1) exploiting the highly polyphagous nature of certain species, (2) exposing predators to artificial diet for multiple generations to incite adaptation, (3) formulating artificial diets to match the texture and chemical composition of preferred natural prey, and (4) encasing the diet within Parafilm® to resemble the shape of natural prey. Encasement may also reduce desiccation and retard spoilage of the diet. Identification of other factitious prey and development of artificial diets that ensure production of predators of high quality should be possible. This review was conducted, for the most part, in support of generalist insect predators used, or having the potential to be used, in augmentative biological control of pests on plants in semi-closed systems, such as greenhouses and interiorscapes.

Occurrence, Density, and Distribution of Parasitic Fungus Hesperomyces virescens (Laboulbeniales: Laboulbeniaceae) on Multicolored Asian Lady Beetle (Coleoptera: Coccinellidae)

Abstract The coccinellid-specific parasitic fungus Hesperomyces virescens Thaxter was found on the multicolored Asian lady beetle, Harmonia axyridis (Pallas), in fall and winter in Lebanon County, Pennsylvania. Research objectives were 1) to determine the density of H. virescens on field-collected H. axyridis adults held in the laboratory, and 2) to determine H. virescens presence, density, and distribution on H. axyridis adults in the field. In the laboratory, male and female H. axyridis adults hosted >150 H. virescens mature thalli (i.e., fruiting bodies); distributed primarily on the elytra and abdomen. At the overwintering site, H. virescens density per host was often <20 mature thalli, which were distributed primarily on the elytra of both sexes. On average, 52.5 and 57.4% of H. axyridis males and females, respectively, hosted H. virescens mature thalli in late winter (5 March 2003); <14% of either sex hosted mature thalli the following fall (15, 22, and 28 October and 10 November 2003) at the same site. This study suggests that H. virescens is an established parasite of H. axyridis in Pennsylvania but that field estimates of infection may vary considerably between dates that adult beetles arrive and depart from overwintering sites. Preponderance of fungal thalli on the dorsum rather than the ventrum of H. axyridis males suggests that mating behavior is not solely responsible for transmission of H. virescens from infected to noninfected adults.

Living with the enemy: parasites and pathogens of the ladybird Harmonia axyridis

Harmonia axyridis is an invasive alien predator in many countries across the world. The rapid establishment and spread of this species is of concern because of the threat it poses to biodiversity as a generalist predator. Understanding the mechanisms that contribute to the success of this species as an invader is not only intriguing but also critical to our understanding of the processes governing such invasions. The enemy release hypothesis (ERH) could explain the rapid population growth of many invasive alien species. However, empirical evidence in support of the ERH is lacking. An alternative hypothesis that could explain rapid population growth is evolution of increased competitive ability (EICA). Here we provide an overview of the parasites and pathogens of coccinellids with a particular focus on H. axyridis as a host. We examine the differential susceptibility of host species and highlight the resilience of H. axyridis in comparison to other coccinellids. We recognise the paucity and limitations of available information and suggest that studies, within a life-table framework, comparing life history traits of H. axyridis in both the native and introduced ranges are necessary. We predict that H. axyridis could benefit from both enemy release and EICA within the introduced range but require further empirical evidence.

Identification of (−)-β-Caryophyllene as a Gender-Specific Terpene Produced by the Multicolored Asian Lady Beetle

This work reports the development and use of techniques for characterizing volatile chemicals emitted by the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in an effort to identify the semiochemicals involved in establishment and persistence of overwintering beetle aggregations. Volatiles emitted from live beetles were detected by using whole-air sampling and solid-phase microextraction (SPME). Adsorbed volatiles were thermally desorbed and identified with gas chromatography-mass spectrometry (GC/MS). By comparing the chromatograms of volatiles emitted from live male and female beetles, a sesquiterpene, (−)-β-caryophyllene, was found only in the females. The identity of (−)-β-caryophyllene was confirmed by using NIST Library searches, comparing retention times with those of known standards, and by using higher-resolution GC/MS above bench top capability. Although SPME trapping detected a wider array of compounds compared to whole-air sampling, the latter method is better suited for automation. Unattended automated sampling is required for the continuous measurement of targeted compounds under dynamically changing incubation conditions. These conditions, mimicking natural overwintering conditions, are essential to our long-term goal of using this technology to detect and identify the aggregation pheromone of H. axyridis.

Potential for Modifying the Behavior of the Multicolored Asian Lady Beetle (Coleoptera: Coccinellidae) with Plant-Derived Natural Products

Abstract Bioassays were conducted to study the effectiveness of selected chemicals to prevent the multicolored Asian lady beetle, Harmonia axyridis (Pallas), from overwintering in buildings. We discovered that certain monoterpenoids elicited avoidance in adults toward treated filter paper within a petri dish bioassay at 1.0 mg/cm2. Camphor and menthol were the most effective of the monoterpenoids tested. Y-tube olfactometer bioassays revealed that beetles spent significantly more time (within 10-min observation periods) in the untreated control arm than in the arm containing camphor or menthol (both at 100 and 1,000 μg). Another olfactometer bioassay revealed that significantly more beetles remained in the untreated control arm than in the arm containing camphor or menthol (142 μg), within 45-min observation periods. When camphor (9.4% emulsified concentrate) was sprayed onto crevices on the exterior of a building through which beetles were entering, 100% of approaching beetles were repelled for the duration of the tests (0.5 h, two replicates). In another field experiment, significantly fewer H. axyridis were captured in traps containing camphor versus un-baited control traps. Research is continuing to develop a protocol for repelling nuisance beetle aggregations and conserving the beetles for biological control applications.

Production of Heteropteran Predators

This chapter addresses several key aspects of rearing procedures for predatory bugs. The value of natural, factitious, and artificial foods for the major species used in biological control is reviewed. Whereas several types of factitious foods are routinely used in the production of heteropteran predators, the adoption of artificial diets in mass production systems has remained negligible. Special attention is given to the implications of zoophytophagy for the production of predatory bugs. The use of plants and plant materials as sources of water and supplementary nutrients, and as living and oviposition substrates, is discussed, as well as the potential of alternative substrates. The impacts of crowding, cannibalism, and the presence of microorganisms on the performance of rearing systems are also addressed. Although important gaps in our ability to produce heteropteran predators are identified, equally important is that production will clearly benefit from new technologies that are rapidly expanding our knowledge of genetics and of developmental and reproductive biology.

Do plant trichomes cause more harm than good to predatory insects

Plants use trichomes as a morphological defense against attacks from herbivores. The literature was reviewed to test the hypothesis that trichome-bearing (pubescent) plants do not cause more harm than good to predators. Forty seven records on interactions between plant trichomes and predatory insects were found. Overall, the records reveal that trichomes have more harmful than beneficial effects on predators. Fortunately, most harmful effects are sublethal; they usually affect movement, development, oviposition and predation potential. In worst cases, sticky exudates from glandular trichomes entrap predators. The hooked tips on non-glandular trichomes impale predators. Entrapped and impaled predators often die from desiccation or starvation. Plant cultivars with high (rather than low) trichome density cause the most harm, and trichomes on tomato and some beans often cause more harm than good to predatory beetles, true bugs and lacewings. Whether these harmful effects have a net negative effect on plant fitness is poorly known and ripe for study. When developing and testing cultivars with increased trichome-based resistance to herbivory, the question as to whether these technologies are compatible with the functional role of those predators (single or combined species) capable of suppressing herbivore populations should be considered.

Lima bean–lady beetle interactions: hooked trichomes affect survival of Stethorus punctillum larvae

We tested the hypothesis that Lima bean Phaseoluslunatus L. (Henderson cultivar) trichome density affects the survival of the acariphagous lady beetle Stethoruspunctillum Weise. When isolated throughout larval development, 10% or less of S. punctillum larvae reared on two-spotted spider mite Tetranychusurticae Koch on small (rather than large) P. lunatus leaves survived until pupation. Although other factors might have contributed to larval mortality, we demonstrated that survival rate was related to trichome density (i.e., number of hooked trichomes per cm on the underside of leaves). Trichome density was greatest on the underside of small leaves and least on large leaves, indicating that survival rate increased as trichome density decreased. Hooked trichomes impaled S. punctillum larvae more often at the apex of the abdomen than at any other body part. Hooked trichomes also trapped S. punctillum adults, but they always managed to free themselves. This study highlights the negative effect of Lima bean hooked trichomes on a predacious lady beetle that attacks the two-spotted spider mite.

Is Tetranychus urticae suitable prey for development and reproduction of naïve Coleomegilla maculata

The lady beetle Coleomegilla maculata De Geer is an omnivorous predator that could help suppress aphid and spider mite populations on plants in greenhouses, plantscapes or interiorscapes. We are assessing the nutritional requirements and feeding behavior of C. maculata on target prey (spider mites) and factitious (unnatural) food. Our ultimate goal is to develop an efficacious diet to mass produce C. maculata. In this study, we tested the hypothesis that Tetranychus urticae Koch (two‐spotted spider mite) is not suitable prey for development and reproduction of naïve C. maculata (i.e., with no prior exposure to T. urticae). Our objectives were to (i) provide baseline data on the effects of consuming T. urticae on C. maculata life history, (ii) to compare the effects of consuming all stages of T. urticae versus eggs of Musca domestica L. (common housefly), and (iii) to determine if the consumption of plant products was beneficial. We used C. maculata from a colony reared only on Ephestia kuehniella Zeller (Mediterranean flour moth) eggs. In experiments, C. maculata larvae were reared from the first instar to adult stage with prey/food in replicated arenas; adult females were paired with a single male with prey/food. The results showed that naïve C. maculata readily attacked and consumed T. urticae. Nevertheless, T. urticae was less suitable than M. domestica eggs for C. maculata development and reproduction. Applying a synthetic pollen‐Chlorella alga powder (SPCA) in arenas containing T. urticae appeared to boost C. maculata female development and reproduction.

Limited Transmission of the Ectoparasitic Fungus Hesperomyces virescens between Lady Beetles

The ectoparasitic fungus Hesperomyces virescens Thaxter (Ascomycota: Laboulbeniales) commonly infects the invasive lady beetle Harmonia axyridis (Pallas) and several other aphidophagous lady beetles in North America and Europe. We tested the hypothesis that bodily contact between adults of different lady beetle species supports horizontal transmission of H. virescens. We used laboratory assays to determine whether H. axyridis or Olla v-nigrum (Mulsant) harboring H. virescens (i.e., source beetles) transmit the fungus to noninfected target beetles H. axyridis, O. v-nigrum, Coccinella septempunctata L., Coleomegilla maculata (De Geer), or Hippodamia convergens Guerin-Meneville. Results indicate that intraspecific transmission (i.e., for the source beetles H. axyridis and O. v-nigrum) was common but interspecific transmission (i.e., from source H. axyridis or O. v-nigrum to target species) was low. Interspecific transmission occurred at low rates from H. axyridis to both C. septempunctata and O. v-nigrum and from O. v-nigrum to both C. septempunctata and H. convergens. Based upon our laboratory assays of forced pairings/groupings of source and target beetles, we predict that horizontal transmission of H. virescens between species of aphidophagous coccinellids is possible but likely rare.