Doug A. Landis

Maximizing arthropod‐mediated ecosystem services in agricultural landscapes: the role of native plants

Beneficial arthropods, including native bees, predators, and parasitoids, provide valuable ecosystem services worth

Early-season predation impacts the establishment of aphids and spread of beet yellows virus in sugar beet

8 billion to US agriculture each year. These arthropod-mediated ecosystem services (AMES) include crop pollination and pest control, which help to maintain agricultural productivity and reduce the need for pesticide inputs. Maximizing survival and reproduction of beneficial arthropods requires provision of pollen and nectar resources that are often scarce in modern agricultural landscapes. Increasingly, native plants are being evaluated for this purpose. Native plants can outperform recommended non-natives and also provide local adaptation, habitat permanency, and support of native biodiversity. We predict that the success of insect conservation programs using flowering plants to increase AMES on farmland will depend on landscape context, with the greatest success in landscapes of moderate complexity. Reintegration of native plants into agricultural landscapes has the potential to support m...

Habitat use patterns by the seven-spotted lady beetle (Coleoptera: Coccinellidae) in a diverse agricultural landscape

AbstractThe potential of predators to impact the establishment of aphid vectors and the spread of beet yellows virus in sugar beet was examined. Myzus persicae carrying beet yellows virus (BYV) were released on six interior sites and six edge sites in each of four fields at the end of May. Aphids established at low densities and BYV was spread in circular patches around the infested plants at all sites. The number of diseased plants per patch at the end of September ranged from a field-average of 130 to 210 in the four fields. There was a weak tendency towards better aphid establishment and greater virus spread in fields in less complex landscapes. Edge sites had less virus spread than interior sites in one field, more virus spread in two other fields, and there was no statistically significant difference in the fourth field.In the field where virus spread was lowest at edge sites, we used predator exclosure and direct observation to manipulate and quantify the effects of early season predation. On a warm day in early June, 81% ofAphis fabae exposed to predators on young beet plants disappeared during a 24 h period, compared to 10% of aphids protected by clipcages. Intermediate levels of predator exclusion, allowing aphids to walk away but restricting predator access, showed that predation was responsible for aphid disappearance.Cantharis lateralis L. (Coleoptera: Cantharidae) was the most frequently observed foliar predator (>90%). It was found eating aphids on several occasions. The incidence of predators was 1.8 per plant per h in the field interior and 3.8 per plant per h. near the edge.In the same field, aphids and virus were released in six edge and six interior sites, that were surrounded by 0.5 m high plastic open-top barriers (‘exclosures’). Pitfall trapping inside the barriers reduced potential soil predator densities to ca. one-tenth of the open field level and arrivals of flying predators were reduced. Inside the exclosures, aphid establishment was enhanced, and virus spread at exclosure sites was increased by about 50% compared to open sites.Foliar and pitfall sampling yielded the following predators:Cantharis lateralis, C. rufa L. (Coleoptera: Cantharidae),Coccinella septempunctata L.,C. undecimpunctata L. (Coleoptera: Coccinellidae),Pterostichus cupreus (L.),Harpalus rufipes (de Geer),Patrobus atrorufus (Strom),Trechus quadristriatus (Schrk.),Bembidion lampros (Herbst) (Coleoptera: Carabidae). In a laboratory no-choice trial (with 10M. persicae /day offered), each of these species ate aphids with consumption rates varying from 1.7 to 9.2 aphids/day.The results show that early predation substantially impacted aphid establishment in one field, and resulted in reduced virus spread. Results in the other fields show that these results cannot be easily generalized.RésuméMyzus persicae, porteur du virus de la jaunisse de la betterave a été lâché en six sites à l’intérieur et en six autres sites sur les bordures de chacun des 4 champs étudiés, à la fin mai. Les pucerons se sont installés à de faibles densités et le virus s’est propagé en des taches circulaires autour des plantes infestées de tous les sites. Le nombre de plantes malades par tache, fin septembre, était compris en moyenne par champ entre 130 et 210 pour les quatre parcelles. Il y avait une faible tendance à une meilleure installation des pucerons et une plus grande transmission des virus dans les champs situés dans les paysages les moins complexes. Les sites de bordure présentaient une transmission de virus plus faible que les sites de l’intérieur dans un des champs, davantage de transmission de virus dans deux autres champs et il n’y avait pas de différence significative dans le quatrième.Dans le champ où la transmission du virus était la plus faible au niveau des sites de bordure, nous avons utilisé une méthode d’exclusion des prédateurs ainsi que l’observation directe dans le but de manipuler et de quantifier les effets de la prédation en début de saison. Au cours d’une journée chaude de début juin, 81% desA. fabae exposés aux prédateurs sur des jeunes plants de betterave ont disparu en 24 heures, comparé à 10% pour les pucerons protégés dans des ‘clips cages’. Des niveaux intermédiaires d’exclusion des prédateurs permettant aux pucerons de partir en marchant mais restreignant l’accès des prédateurs, ont montré que la prédation était responsable de la disparition du puceron.Cantharis lateralis L. (Col., Cantharidae) était le prédateur le plus fréquement observé sur le feuillage (>90%). Il a été trouvé à différentes occasions en train de consommer des pucerons. L’incidence des prédateurs était de 1,8 par plante/heure à l’intérieur de la parcelle et 3,8 par plante/ heure près des bordures. Dans le même champ, des pucerons et du virus ont été déposés dans 6 sites intérieurs et six sites de bordure qui étaient entourés de barrières de plastique de 0,5 m de haut ouvertes à la partie supérieure. Des pièges de Barber placés à l’intérieur de ces barrières réduisaient la densité des prédateurs potentiels à 1/10 du niveau du champ; l’arrivée de prédateurs volant était également réduite. A l’intérieur de ces barrières, l’installation des pucerons était favorisée et la dissémination était augmentée d’environ 50 % par rapport aux sites ouverts.La collecte sur le feuillage et dans les pièges a permis de capturer les prédateurs suivants :Cantharis lateralis, C. rufa L. (Coleoptera : Cantharidae),Coccinella septempunctata L.,C. undecimnotata L. (Col. : Coccinellidae),Pterostichus cupreus (L.),Harpalus rufipes (de Geer),Patrobus atrorufus (Strom),Trechus quadristriatus (Schrk.),Bembidion lampros (Herbst) (Col. : Carabidae). Dans un essai de laboratoire sans choix (avec 10M. persicae présentés par jour), chacune des espèces précédentes a consommé des pucerons à un rythme variant de 1,7 à 2,2 pucerons /jour. Ces résultats montrent que la prédation précoce a réduit sérieusement l’installation des pucerons dans un champs et a diminué la dissémination du virus. Les résultats des autres champs montrent que ces résultats ne peuvent pas être facilement généralisés.

Ground predator abundance affects prey removal in highbush blueberry (Vaccinium corymbosum) fields and can be altered by aisle ground covers

Abstract Studies were conducted during 1989 and 1990 to describe the habitat use patterns of the seven-spotted lady beetle, Coccinella septempunctata Linnaeus. The study site consisted of seven treatments arranged in forty-two 0.91-ha plots. Maize, soybean, wheat, alfalfa, Populus, and successional habitats were represented. Habitats were sampled weekly (from late May to the end of August) using yellow sticky traps, sweep net samples, and visual observations. C. septempunctata was detected in all habitats during both years. Habitat preference, however, depended upon availability of prey and habitat disturbance. In 1989, wheat supported C. septempunctata populations early and mid-season, while Populus supported more C. septempunctata later in the season. In 1990, alfalfa was dominant early in the season, soybean in the mid-season, and successional and alfalfa late in the season. The results indicate that both cultivated and uncultivated habitats play an important role in supporting populations of C. septempunctata.

Effect of food resources on adult Glyptapanteles militaris and Meteorus communis (Hymenoptera: Braconidae), parasitoids of Pseudaletia unipuncta (Lepidoptera: Noctuidae)

Habitat management to conserve natural enemies has increased biological control of insect pests in various cropping systems [Annu. Rev. Entomol. 45: 175–201, 2000]. We wanted to determine if insect predation in highbush blueberry, Vaccinium corymbosum L. (Ericales: Ericaceae), is influenced by manipulation of edaphic arthropod community and whether management of ground cover in aisles between blueberry rows enhances this community. The first question was studied in blueberry plots bounded by trenches permitting selective movement into plots (ingress) or out of plots (egress), as well as unbounded control plots. We observed a significant effect of boundary type on the arthropod communities’ relative abundance as measured with pitfall traps, with relative abundance highest in ingress plots, intermediate in control plots and lowest in egress plots. Effects of ground arthropod abundance on predation rates were assessed with onion fly, Delia antiqua (Meigen) (Diptera: Anthomyiidae), pupae as sentinel prey. Pupa recovery was greatest in egress boundary plots, intermediate in control plots and lowest in ingress boundary plots. Regression analyses indicate pupal recovery rate decreased as a function of carabid abundance as well as the abundance of non-insect ground predators. To determine if ground cover management influenced natural enemy abundance, aisles were clean cultivated or planted with three ground covers (clover, ryegrass, or buckwheat). Increasing ground cover had a significant effect on the relative abundance of Harpalus pensylvanicus De Geer (Coleoptera: Carabidae). In addition to conserving natural enemies for control of blueberry insect pests, we discuss additional benefits of ground covers that may increase their utility for blueberry production.

Visual response of Coccinella septempunctata (L.), Hippodamia parenthesis (Say), (Coleoptera: Coccinellidae), and Chrysoperla carnea (Stephens), (Neuroptera: Chrysopidae) to colors

Abstract Adult parasitoids frequently require access to food and adequate microclimates to maximize host location and parasitization. Realized levels of parasitism in the field can be significantly influenced by the quantity and distribution of extra-host resources. Previous studies have demonstrated a significant effect of landscape structure on parasitism of the armyworm Pseudaletia unipuncta (Haworth) (Lepidoptera: Noctuidae). As a possible mechanism underlying this pattern, we investigated the effect of carbohydrate food sources on the longevity and fecundity of armyworm parasitoids under laboratory conditions of varying temperature, host availability, and mating status. Glyptapanteles militaris (Walsh) (Hymenoptera: Braconidae) adults lived significantly longer when provided with honey as food and when reared at 20°C versus 25°C. Meteorus communis (Cresson) (Hymenoptera: Braconidae) adults also lived significantly longer when provided with honey, although longevity was reduced when females were provided hosts. Honey-fed females of M. communis parasitized significantly more hosts because of their increased longevity, but did not differ in daily oviposition from females provided only water. Mating significantly increased parasitism by honey-fed M. communis, but not those provided water alone. These results indicate that the presence of both carbohydrate resources and moderated microclimates may significantly increase the life span and parasitism of these parasitoids. However, the greater longevity and lower daily rate of oviposition of M. communis suggest that food and microclimate resources are more critical for this species than for the shorter lived, gregarious G. militaris. These findings contribute to our understanding of how these two parasitoids respond to landscape complexity.

Corn Phenology Influences Diabrotica virgifera virgifera Emigration and Visitation to Soybean in Laboratory Assays

Abstract The response of the seven-spotted lady beetle, Coccinella septempunctata (L.) (Coleoptera: Coccinellidae), the parenthesis lady beetle, Hippodamia parenthesis (Say), (Coleoptera: Coccinellidae), and the green lacewing, Chrysoperla carnea (Stephens), (Neuroptera: Chrysopidae) to seven colors was evaluated in the field using sticky panels. C. septempunctata exhibited a strong positive response to yellow. C. carnea showed a preference for yellow, green, and red. H. parenthesis did not exhibit strong visual orientation to any color. Programs aimed at monitoring these predators should consider their visual responses to colors in designing monitoring systems.

Maximizing ecosystem services from conservation biological control: The role of habitat management

Abstract We used two types of laboratory apparatus to test whether rotation-resistant and wild-type Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) responded differently to corn phenology. Beetles from Nebraska where injury to rotated corn has not been reported were defined as wild type, and beetles from Illinois where injury to rotated corn is common represented “rotation-resistant” populations. A two-chamber emigration arena assayed propensity of both populations to leave corn during and after anthesis. A side-arm olfactometer tested whether the relative attraction of beetles to soybean versus corn was influenced by corn phenology. Beetle origin did not influence departure from corn of varying phenology; both emigrated significantly less from young (shedding pollen) than old (no pollen) corn. Significantly more beetles entered olfactometer chambers with soybean than empty control chambers, but there was no difference in response between the two populations. Numbers of beetles entering chambers with soybean varied with the addition of young versus old corn. Replacing young with old corn approximately doubled the percentage of beetles not selecting corn. As corn aged, adult visitation of soybean increased significantly. We suggest this mechanism is sufficient to explain injury to rotated corn, when linked to a corn crop planted early and synchronously within a landscape limited to corn and soybean. This explanation based on preexisting behavioral plasticity should be given due consideration along with conceptual models of D. v. virgifera rotation resistance that imply genetic change.