Tatyana A. Rand

The wheat stem sawfly, Cephus cinctus Norton (WSS, Hymenoptera: Cephidae), is a major pest of wheat in the U.S. Great Plains. While populations of the larval parasitoids Bracon cephi and B. lissogaster (Hymenoptera: Braconidae) are abundant in wheat-growing regions of some states, they remain low in Colorado. To determine whether reduced parasitism reflects local parasitoid population differentiation or ecological constraints, we combined greenhouse parasitism assays with mitochondrial cytochrome oxidase I (COI)-based population genetic analyses of WSS and Bracon cephi collected from Colorado, Nebraska, and North Dakota. Greenhouse assays showed no differences in parasitism rates of Colorado WSS among Bracon populations from different states, indicating compatibility across regions. However, COI analyses revealed contrasting genetic patterns between host and parasitoid. WSS populations exhibited strong regional genetic differentiation, with Colorado samples showing evidence of recent demographic expansion, including a star-like haplotype pattern centered on a dominant haplotype and a significantly negative Tajima’s D. Nebraska displayed the highest WSS haplotype diversity, while North Dakota samples clustered within the northern haplogroup. In contrast, B. cephi populations showed little geographic structure with haplotypes broadly shared among regions. AMOVA analyses revealed substantial genetic differentiation among WSS populations (56.52%), whereas B. cephi showed no detectable population structure, with most of the variation within populations. Low parasitism in Colorado appears consistent with ecological or demographic factors associated with recent WSS expansion rather than genetic incompatibility. These findings highlight the evolutionary history of the genetic structure of WSS and Bracon populations, providing insights for biological control strategies in WSS management.

Lobesiodes euphorbiana (Freyer) (Lepidoptera: Tortricidae), commonly known as the spurge leaf tying moth, was intentionally introduced into Canada in the 1980s as a biocontrol agent for leafy spurge, Euphorbia virgata Waldstein and Kitaibel (Euphorbiaceae). The moth has never been reported in the United States of America, where it was not approved for release as a biocontrol agent. Here, we report the first records of L. euphorbiana in Montana and North Dakota, United States of America.

In grassland ecosystems, oil and gas production areas require vegetation reclamations once extractions are completed. These reclamations take years to accomplish and may appear similar to the surrounding undeveloped grasslands. To test whether reclaimed oil/gas pads successfully recover ecological communities, we collected and utilized carabid beetles (Coleoptera: Carabidae) as bioindicators of reclamation success. We compared carabid beetle communities on well pad reclamations and within undisturbed native prairie 50 m and 150 m from the well pad reclaim edges. Overall, we found lower carabid richness and abundance in native prairie at the 150-m distance compared to the well pad reclaims, with the 50 m distance generally falling between the two. The differences in carabid communities likely reflect previously documented differences in vegetation types and structure within the reclaimed well pads that have persisted for decades after reclamation. These reclaimed habitats may be acting as “islands” for certain carabid species, representing population sources or sinks that likely influence carabid dynamics within the adjacent native prairie. These findings demonstrate a long-term signature of development disturbance in the landscape.

Novel crop rotation is an important factor influencing the composition of soil microorganisms. However, the effect of introducing oilseed and cover crops (CCs) into monoculture durum rotations on soil microbial communities is not clear in the Northern Great Plains. The objective of this study was to evaluate the effects of 2-year durum (Triticum durum D.) rotations with Ethiopian mustard (Brassica carinata A.) or camelina (Camelina sativa L.) or a 10-species forage/CC mix planted to replace fallow rotations with wheat on soil microorganisms. This study was designed as a randomized complete block with three replications in a no-tillage system. The results showed that total bacterial proportion was significantly higher in durum following fallow and camelina compared to durum following CC and carinata. Total fungal proportion was significantly higher in durum following CC compared to durum following oilseed crops and fallow. The fungal-to-bacterial ratio was significantly higher in durum following CC compared to durum following camelina and fallow. The crop species, soil pH and highly variable rainfall influenced the microbial community dynamics. The abundance of specific microbial groups due to crop-related changes might play a key role in the yield of subsequent crops and soil biological health. This study provides valuable insights into the use of CC mix and oilseeds as an alternative crop for fallow in a wheat–fallow system under dryland farming conditions. Future work is required to elucidate the biological mechanisms and functions of the soil microbial communities in the preceding and subsequent crop relative to soil health and crop productivity.

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a major pest of wheat (Triticum aestivum L., Poales: Poaceae) across the northern Great Plains of North America. Cephus cinctus has a wide host range, attacking numerous wild grasses and cultivated cereals in crop and grassland habitats, where it is, in turn, attacked by 2 native braconid parasitoids. Quantitative assessments of C. cinctus infestation and parasitism levels in different grass species across the full spectrum of available hosts are important in assessing the extent to which grasslands, or specific constituent grass species, may be reservoirs of pests or parasitoids moving into wheat. We quantified infestation and parasitism levels in over 25,000 stems collected from 17 grass species and wheat spanning 35 sites in central Montana, United States, over 2 yr. Infestation levels in 5 grass species, primarily wheatgrasses, were high (38%–65%) and similar to the levels observed in wheat (55%). In contrast, the majority of grass species (12 of 17) had significantly lower levels of infestation (C. cinctus. Parasitism levels in highly infested wheatgrasses were, on average, 3 times higher than those in cultivated wheat, suggesting that these grasses could provide important conservation habitat for parasitoids. Future work examining the relative performance of pests and parasitoids in these grasses will be important in gauging their relative value as plant materials to bolster parasitoid conservation in reseeded grassland habitats.

The composition of a soil microbial community that is associated with novel rotation crops could contribute to an increased yield of subsequent crops and is an important factor influencing the composition of the rhizosphere microbiome. However, the effect of alternative dryland crops on soil microbial community composition is not clear in the northern Great Plains (NGP). The objective of this study, therefore, was to evaluate the effects of the oilseed crops Ethiopian mustard (Brassica carinata A.) or camelina (Camelina sativa L.) or a 10-species forage/cover crop (CC) mix and fallow on soil biological health. Phospholipid fatty acid (PLFA) analysis was used to characterize the microbial community structure. The results showed that the total bacterial PLFA proportion was significantly higher in camelina and fallow compared to CCs and carinata, whereas the total fungal proportion was significantly higher under a CC mix compared to camelina and fallow. The fungal-to-bacterial ratio was significantly higher in CCs (0.130) and carinata (0.113) compared to fallow (0.088). Fungi are often considered a good indicator of soil health, while bacteria are crucial in soil functions. The changes in specific microbial communities due to crop-related alterations might play a key role in the yield of subsequent crops. This study provides valuable insights into the effect of oilseeds, CCs, and fallow on microbial communities.

The absence of sugar resources can be an important factor in limiting the success of parasitoids as biological control agents. Restoring vegetation complexity within agricultural landscapes has thus become a major focus of conservation biological control efforts, with a traditional emphasis on nectar resources. Aphid honeydew is also an important source of sugars that is infrequently considered. We carried out a laboratory experiment to examine the potential effects of honeydew from six different aphid species by crop species combinations on the longevity of Bracon cephi Gahan (Hymenoptera: Braconidae), the most important biological control of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), a major pest of wheat in the northern Great Plains of North America. The benefits of honeydew for parasitoid longevity varied significantly among different aphid and crop species, illustrating the complexity of these interactions. However, honeydew produced by four aphid species commonly found in wheat, pea, and canola crops significantly increased the longevity (by two- to threefold) of the parasitoid. The study suggests that honeydew provisioning could be an important mechanism underlying the benefits of crop diversification to support biological control that merits further research.