Julie A. Peterson

Integration of Plant Defense Traits with Biological Control of Arthropod Pests: Challenges and Opportunities

Crop plants exhibit a wide diversity of defensive traits and strategies to protect themselves from damage by herbivorous pests and disease. These defensive traits may be naturally occurring or artificially selected through crop breeding, including introduction via genetic engineering. While these traits can have obvious and direct impacts on herbivorous pests, many have profound effects on higher trophic levels, including the natural enemies of herbivores. Multi-trophic effects of host plant resistance have the potential to influence, both positively and negatively, biological control. Plant defense traits can influence both the numerical and functional responses of natural enemies; these interactions can be semiochemically, plant toxin-, plant nutrient-, and/or physically mediated. Case studies involving predators, parasitoids, and pathogens of crop pests will be presented and discussed. These diverse groups of natural enemies may respond differently to crop plant traits based on their own unique biology and the ecological niches they fill. Genetically modified crop plants that have been engineered to express transgenic products affecting herbivorous pests are an additional consideration. For the most part, transgenic plant incorporated protectant (PIP) traits are compatible with biological control due to their selective toxicity to targeted pests and relatively low non-target impacts, although transgenic crops may have indirect effects on higher trophic levels and arthropod communities mediated by lower host or prey number and/or quality. Host plant resistance and biological control are two of the key pillars of integrated pest management; their potential interactions, whether they are synergistic, complementary, or disruptive, are key in understanding and achieving sustainable and effective pest management.

Scanning electron microscope study of molar-surface development of Artemia franciscana Kellogg (Anostraca)

ABSTRACT Development of the molar surface of the mandible of Artemia franciscana was studied with scanning electron microscopy. The molar surface of larval stage 1 consists of tapered, cuticular bristles. The mandibular palps and mandibles are biramous, and a gnathobasic spine (but no short spines) is present on each mandible. By larval stage 3, cuticular teeth emerge on the posterior part of the molar surface. The number of teeth and the number of cusps per tooth generally increase as the brine shrimp proceeds through the ninth molt. Short spines, occurring either singly or in groups, appear on the ventral and dorsal surfaces of the mandibles at approximately larval stage 9. The molar surface of larval stage 10 is multifaceted and dramatically different from that of the preceding stage. It has three regions: the anteroventral, the transition, and the posterodorsal. By larval stage 11, the gnathobasic spine has completely degenerated. During larval stages 11―17, the anteroventral region changes from irregular ridges of small, unbranched minor cusps to as many as 22 parallel ridges. Minor cusps remain on the dorsal edge of each ridge, but progress ventrally toward branched, fingerlike projections. Each ridge terminates in a marginal tooth at the ventral edge, thus comprising the ventral fringe. The posterodorsal region changes from one row of rounded teeth to as many as three rows of sharp, conical, stout teeth. The transition region bears projections intermediate between those found on the anteroventral and posterodorsal regions.

Intraguild interactions and behavior of Spodoptera frugiperda and Helicoverpa spp. on maize

BACKGROUND Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is one of the major pests of maize and is in the same feeding guild as the noctuid pests Helicoverpa zea (Boddie) and Helicoverpa armigera (Hübner), recently reported in South and North America. The intraguild interactions of these species were assessed in laboratory and field conditions by determining the survival of larvae in interaction scenarios with non-Bt maize silks and ears. Moreover, a video tracking system was utilized to evaluate behavioral parameters during larval interactions in scenarios with or without food. RESULTS In intraguild interactions, S. frugiperda had greater survival (55-100%) when competing with Helicoverpa spp. in scenarios where larvae were the same instar or when they were larger (fourth versus second) than their competitor. Frequency and time in food of S. frugiperda larvae were negatively influenced by interactions. Larvae of S. frugiperda moved shorter distances (less than 183.03 cm) compared with H. zea. CONCLUSION Overall, S. frugiperda had a competitive advantage over Helicoverpa spp. This study provides significant information regarding noctuid behavior and larval survival during intraguild interactions, which may impact pest prevalence and population dynamics, thereby affecting integrated pest management and insect resistance management of these species in maize.