Conversely, warmer temperatures may lead to increased exposure to pathogens and pests or to reduced survival due to intensifying summer droughts or extended winter freeze–thaw cycles . It should be noted that any herbarium-based study of this magnitude is susceptible to the criticism that it includes potentially faulty records, either because of differing biases among collectors in the timing and location of collection, or because of limited documentation of the error distances associated with georeferencing of each specimen. Previous examinations of herbarium collections have found, for example, that collection effort is often concentrated at locations that are easily accessed and may also avoid periods of severe inclement weather such as intense storms or blizzards . However, multiple studies have determined that estimates of phenological change keep pace with estimates of phenological change derived from in situ data sources, indicating that collector preferences in the timing of collection are unlikely to produce systematic bias in the resulting estimates of flowering time or phenological advancement . Similarly, while the rarity with which estimates of georeferencing accuracy are recorded in digital specimen data limits our ability to directly analyze the effects of georeferencing errors on this analysis, blueberry pot such errors are more likely to be a source of noise rather than of systematic bias in a study of this scale.
To produce systematic biases in the resulting data, locations associated with large error distances would be required to be biased toward locations with frost risks that differed in a specific direction . Furthermore, such biases would be required to persist across records produced and georeferenced by many different collectors and multiple independent institutions, all of which would be required to exhibit similar directional or climatic biases. It should also be noted that these results represent broad regional patterns in frost risk among 1,653 taxa across a large portion of the continental US. As this study documents, a significant proportion of taxa have exhibited increased frost risk post-1979. While beyond the scope of the current study, certain regions or floras have likely exhibited lesser reductions in frost risk than were observed across the broad spatial scales examined in this study. Furthermore, examinations of frost risk to various crop species have indicated that microclimate variations that occur at smaller scales than can be observed in this study may also play significant roles not only in determining local temperature but also in the process of ice nucleation, thereby affecting the resulting risk of frost-related damage to plant reproductive tissues . Nevertheless, the results presented here are consistent with broad-scale models of past and present frost risk to vegetative tissues among native tree species , indicating that, for the majority of species and in the majority of locations, frost risk to reproductive tissues is likely to be decreasing as a result of progressive climate changes.
While the effects of these changes will likely produce complex impacts on fruit and seed production across taxa and throughout North America, understanding the degree to which broad, systematic shifts in frost risk, phenology, and other ecological processes are occurring among taxa in response to recent climate change remains critical to understanding the broad-scale effects of climate change. Broad generalizations about the phenology of a flora at regional or continental scales, however, require historical data that are both temporally deep and spatially extensive. By leveraging the wealth of data presented by herbarium specimens and other natural history collections data, we may seek and identify broad, climate-driven patterns in reproductive phenology . By demonstrating that recent warming has produced a systematic reduction in frost risk to floral tissues throughout the North American flora, this study highlights a critical aspect of the effects of future climate change, and the likelihood that future warming will further reduce frost risk across the majority of taxa across North America.ISmith, 2019. Nevertheless, the results presented here are consistent with broad-scale models of past and present frost risk to vegetative tissues among native tree species , indicating that, for the majority of species and in the majority of locations, frost risk to reproductive tissues is likely to be decreasing as a result of progressive climate changes. While the effects of these changes will likely produce complex impacts on fruit and seed production across taxa and throughout North America, understanding the degree to which broad, systematic shifts in frost risk, phenology, and other ecological processes are occurring among taxa in response to recent climate change remains critical to understanding the broad-scale effects of climate change.
Broad generalizations about the phenology of a flora at regional or continental scales, however, require historical data that are both temporally deep and spatially extensive. By leveraging the wealth of data presented by herbarium specimens and other natural history collections data, we may seek and identify broad, climate-driven patterns in reproductive phenology . By demonstrating that recent warming has produced a systematic reduction in frost risk to floral tissues throughout the North American flora, this study highlights a critical aspect of the effects of future climate change, and the likelihood that future warming will further reduce frost risk across the majority of taxa across North America.are above 53.5°F . During the first flight, the female glues single eggs to flat surfaces on or near the flower cluster; second and third-generation eggs are laid on grape berries. Larvae form webbed nests; the first-generation larvae feed on flowers before and during bloom in Northern California; second-generation larvae feed on green berries; and third-generation larvae feed inside ripening berries. Larvae create distinctive round holes in prebloom flowers and ripening fruit, which distinguishes their feeding damage from that of other common Lepidoptera larvae found in California vineyards . Feeding damage to berries by second- and third-generation larvae exposes them to infection by Botrytis and other secondary fungi that can be economically damaging.On October 7, 2009, USDA confirmed the presence of EGVM in Napa County. A federal order issued by USDA in June 2010 initiated a quarantine area within 5 miles of all detections . Detections were defined as two or more adult moths trapped within 3 miles of each other during the same life cycle or immature stages confirmed to be EGVM by DNA analysis. The order indicated plant host species as well as plant parts, products, farming and processing equipment, and green waste residues as regulated articles that could not be transported interstate from a quarantine area except under specific conditions. The state interior quarantine enforced restrictions parallel to those in the federal order for intrastate movement of regulated articles within or from quarantine areas. In 2012, the quarantine buffer was reduced from 5 miles to 3 miles around detections. This change accommodated the program’s need to reduce the cost of implementation while acknowledging the adult moths’ short-distance natural dispersal .Immediately after the first confirmed detection in 2009, USDA, CDFA and the Napa County agricultural commissioner deployed 248 sex pheromone–baited traps to delimit the population. However, very few moths were caught because traps were deployed at the end of the third flight . In addition to the trap captures, ground surveys in 2009 recorded 26 larvae, eight pupae and one female at multiple sites in two distinct areas of Napa County. As a result, nursery pots the state interior quarantine was established in March 2010, over an area totaling 162 square miles in Napa County . In February 2010, trapping efforts expanded throughout all grape-growing regions of California — roughly 803,000 acres . Traps were deployed at densities of nine to 16 or 25 traps per square mile of planted vineyard outside and inside the regulated area, respectively . In select urban areas, traps were placed on potential EGVM host plants at a density of five traps per square mile . By the end of 2010, the quarantine area included portions of eight California counties, totaled 2,091 square miles and contained approximately 150,760 acres of vineyards . Subsequently, in 2011, traps detected moths in two additional counties, bringing the total number of regulated counties to 10 and a peak quarantine area of 2,335 square miles .
Trap captures in Napa County indicated a large, widely distributed population, whereas populations in other counties were significantly smaller and more contained . The EGVM regulatory program has relied heavily on the use of pheromonebaited sticky traps to detect moth populations. UC scientists evaluated the efficacy and longevity of four pheromone lures in replicated field experiments in Napa during the first and second moth flights of 2010 . All lures were effective for monitoring EGVM male moth populations during and beyond the period recommended by the manufacturer .In November 2009, USDA assembled a technical working group of subject-matter experts to provide urgent scientific recommendations to regulatory program managers in California. The TWG included university scientists from Italy, France, Germany, Spain, Chile and California, as well as USDA scientists and a representative of the wine grape industry. TWG members continue to meet annually to review program activities and provide technical expertise on topics as diverse as insect biology, detection strategies, handling of harvested fruit and winery waste, and management activities. Since 2010, TWG members have agreed that eradication of EGVM from California remains a realistic goal as long as the population did not become substantially more widespread than was known at that time, the grape industry remained supportive of the effort and effective control methods were available for use by the program . Over the course of the EGVM program, TWG members evaluated research data and program developments to formulate recommendations based on the insect’s biology. Government agencies matched these recommendations to political and fiscal analyses to formulate and deliver the EGVM program.Treatment areas. Treatment areas were defined within a requisite distance from all detections and included agricultural, residential and commercial properties. In 2010, the distance was not standardized, so the size of the treatment areas varied by county. Following a review of the scientific literature suggesting that EGVM are short-distance fliers, the TWG recommended a treatment area within 1,640 feet of all detections regardless of when the detection occurred. From 2013 onward, the TWG modified this recommendation to account for timing of the detection: Treatment areas came to be defined as within 500 m of detections occurring in the current year and previous 2 years. Within the treatment areas,grape and olive were the targeted hosts of concern, and total vineyard acreage varied considerably by county and year . The specific combination of tools used in treatment areas differed by land use and occurrence of potential host plant species. Insecticide program. The recommended insecticide program for EGVM in California vineyards targets the eggs and larvae and includes at least one application of a conventional insecticide or at least two applications of an organic insecticide for each of the first two generations . Although treatment of the first generation is not typical in the Palearctic regions, the TWG determined that treating the first two generations in California would provide the greatest opportunity to eradicate populations. In early 2010, UC scientists provided an exhaustive list of potential insecticides for EGVM management based on a review of the scientific literature. From this list, EGVM program leaders made a concerted effort to identify and recommend products that would provide selective control of EGVM while minimizing risks to nontarget organisms and the environment. The availability of organic treatment options ensured that growers could maintain organic certification while complying with the eradication effort. Pesticide use reporting data for Napa County indicate that growers used a combination of the recommended materials . Insecticide efficacy trials. UC scientists conducted field trials in commercial vineyards in Napa in 2010 to evaluate the efficacy of registered insecticides for EGVM. Chlorantraniliprole, methoxyfenozide, spinosad and Bacillus thuringiensis provided control of young larvae; abamectin, indoxacarb and spinetoram provided the best control of mature larvae . These results were widely distributed to the program team and grape growers. Insecticide treatment. Selective insecticides are most effective if applied when the pest is at its most susceptible stage . In Napa County, UC scientists monitored the male flight, egg and larva development and calculated degree-days from a biofix of January 1 for each life stage . Referencing these observations and calculations to local weather data and vine phenology, UC scientists then determined the optimal timing for insecticide applications for all affected locations in California.