Observations on the Overwintering Potential of the Striped Cucumber Beetle (Coleoptera: Chrysomelidae) in Southern Minnesota

The striped cucumber beetle, Acalymma vittatum (Fabricius) (Coleoptera: Chrysomelidae), is an important pest of cucurbit crops. However, the overwinter- ing capacity of this pest in temperate regions is poorly understood. In this study, the in-field survival of A. vittatum was examined during three consecutive winters. In addition, the supercooling points of A. vittatum were determined as an index of cold hardiness for adults. During each winter, the survival of adults decreased significantly through time, with no individuals surviving until spring. By comparing the supercooling points and in-field survival of adults to soil temperatures, it appears that winter temperatures in Minnesota are cold enough to induce freezing of the beetles. Moreover, a considerable amount of mortality occurred before minimum monthly soil temperatures dropped below the supercooling point of overwintering individuals, suggesting the occurrence of prefreeze mortality. An improved understanding of the response of A. vittatum to winter temperatures in temperate regions may aid in early season management of this pest

Observations on the Overwintering Potential of the Striped Cucumber Beetle (Coleoptera: Chrysomelidae) in Southern Minnesota

The striped cucumber beetle, Acalymma vittatum (Fabricius) (Coleoptera: Chrysomelidae), is an important pest of cucurbit crops. However, the overwinter- ing capacity of this pest in temperate regions is poorly understood. In this study, the in-field survival of A. vittatum was examined during three consecutive winters. In addition, the supercooling points of A. vittatum were determined as an index of cold hardiness for adults. During each winter, the survival of adults decreased significantly through time, with no individuals surviving until spring. By comparing the supercooling points and in-field survival of adults to soil temperatures, it appears that winter temperatures in Minnesota are cold enough to induce freezing of the beetles. Moreover, a considerable amount of mortality occurred before minimum monthly soil temperatures dropped below the supercooling point of overwintering individuals, suggesting the occurrence of prefreeze mortality. An improved understanding of the response of A. vittatum to winter temperatures in temperate regions may aid in early season management of this pest

Polarization control at the microscopic and electronic structure observatory

The new Microscopic and Electronic Structure Observatory (MAESTRO) at the Advanced Light Source (ALS) in Berkeley provides X-rays of variable polarization, produced by an elliptically polarized undulator (EPU), for angle resolved photoemission (ARPES) and photoemission electron microscopy (PEEM) experiments. The interpretation of photoemission data, in particular of dichroism effects in ARPES, requires the precise knowledge of the exact polarization state. Numerical simulations show that the first harmonics of the EPU at MAESTRO provides soft X-rays of almost 100% on axis polarization. However, the higher harmonics as well as the downstream optical elements of the beamline, have a considerable impact on the polarization of the light delivered to the experimental end-station. Employing a simple reflective polarimeter, the polarization is characterized for variable EPU and beamline settings and the overall degree of polarization in the MAESTRO end-stations is estimated to be on the order of 83%

Survival of imported fire ant species subjected to freezing and near freezing temperatures

Originally from the floodplain of the Paraguay River in South America, imported fire ants are well known pests throughout the southern United States. The black imported fire ant, Solenopsis richteri Forel, and the red imported fire ant, Solenopsis invicta Buren, are believed to have arrived in the United States through Mobile, Alabama, in ships\u27 ballast or dunnage in 1918 and the 1930s, respectively. Current federal quarantine area for fire ants covers portions of 13 states and Puerto Rico including twenty-nine counties in Tennessee. The top northern portion of the fire ant range (northern Mississippi and Alabama, and southern Tennessee from Shelby Co. to Giles Co.) is inhabited primarily by S. richteri. The remaining range is occupied by S. invicta with the exception of a sizable band of territory between the parent species that stretches west of the Smoky Mountains to the Mississippi River, which is dominated by their hybrid. A similar pattern of species distribution occurs in their native lands in Argentina, Paraguay, Brazil, and Uruguay. Two experimental parameters, supercooling point and survival under extended low temperature exposure, were used to examine effects of species and individual size in S. richteri, S. richteri x invicta hybrid, and S. invicta, and the effect of Thelohania solenopsae (Knell, Allen, and Hazard) infection in S. invicta on low temperature survival. Supercooling point is the lowest temperature the insect can be brought to before freezing. Based on supercooling point results for fall-collected ants, S. richteri was more cold hardy than the hybrid as shown through a significantly lower supercooling point in large- and small-sized workers. The spring-collected groups did not show this trend, and instead, the hybrid supercooled lower in the large-sized ants and there was no significant difference in the small-sized ants. Winter-collected large and small S. invicta infected with T. solenopsae supercooled to lower temperatures than those not infected. However, spring-collected colonies gave the opposite result. Large spring-collected S. richteri workers had supercooling points not significantly different from the S. invicta, but the hybrid had a significantly lower supercooling point than the parent species. Small hybrid ants were not significantly different from S. richteri, but the S. invicta supercooled to a significantly lower temperature. In the extended exposure tests, the chilling injury of imported fire ants was measured through monitoring ant mortality during 15 days of exposure to one of three temperature regimes: +4°C, +0.5°C, and -4°C. Under the +4°C regime, both the hybrid and S. invicta infected with T. solenopsae had significantly lower mortality rates than either the S. richteri or the uninfected S. invicta by day seven. The +0.5°C regime caused increased ant mortality when compared to the +4°C regime, and the hybrids had significantly lower mortality than uninfected S. invicta from day five through the last day of exposure. The S. richteri and infected S. invicta were not significantly different. One hundred percent mortality was reached within all groups by day seven in the negative temperature regime. The uninfected S. invicta was consistently less cold tolerant than the other groups. At all three regimes, the uninfected S. invicta had the highest mortality and the hybrid had the lowest of all groups. The supercooling point does not seem to be an appropriate measure of cold hardiness in imported fire ants. It is too easily affected by outside phenomena, such as time in the lab and thermocouple size. The differences among the supercooling points of different ant groups were not consistent and these significant differences slight, in light of natural cold weather phenomena. Furthermore, results from the extended exposure tests displayed fire ant mortality at temperatures well above their supercooling points. These results support the hypothesis that extended cold injury causes winterkill of fire ants, and may partially explain the species distribution of fire ants

Could natural selection change the geographic range limits of light brown apple moth (Lepidoptera, Tortricidae) in North America?

We artificially selected for increased freeze tolerance in the invasive light brown apple moth. Our results suggest that, by not accounting for adaptation to cold, current models of potential geographic distributions could underestimate the areas at risk of exposure to this species

How crickets become freeze tolerant: the transcriptomic underpinnings of acclimation in Gryllus veletis

Some ectotherms can survive internal ice formation. In temperate regions, freeze tolerance is often induced by decreasing temperature and/or photoperiod during autumn. However, we have limited understanding of how seasonal changes in physiology contribute to freeze tolerance, and how these changes are regulated. During a six week autumn-like acclimation, late-instar juveniles of the spring field cricket Gryllus veletis (Orthoptera: Gryllidae) become freeze tolerant, which is correlated with accumulation of low molecular weight cryoprotectants, elevation of the temperature at which freezing begins, and metabolic rate suppression. We used RNA-Seq to assemble a de novo transcriptome of this emerging laboratory model for freeze tolerance research. We then focused on gene expression during acclimation in fat body tissue due to its role in cryoprotectant production and regulation of energetics. Acclimated G. veletis differentially expressed more than 3,000 transcripts in fat body. This differential expression may contribute to metabolic suppression in acclimated G. veletis, but we did not detect changes in expression that would support cryoprotectant accumulation or enhanced control of ice formation, suggesting that these latter processes are regulated post-transcriptionally. Acclimated G. veletis differentially regulated transcripts that likely coordinate additional freeze tolerance mechanisms, including upregulation of enzymes that may promote membrane and cytoskeletal remodelling, cryoprotectant transporters, cytoprotective proteins, and antioxidants. Thus, while accumulation of cryoprotectants and controlling ice formation are commonly associated with insect freeze tolerance, our results support the hypothesis that many other systems contribute to surviving internal ice formation. Together, this information suggests new avenues for understanding the mechanisms underlying insect freeze tolerance