Dating of a large tool assemblage at the Cooper's Ferry site (Idaho, USA) to ~15,785 cal yr B.P. extends the age of stemmed points in the Americas.

The timing and character of the Pleistocene peopling of the Americas are measured by the discovery of unequivocal artifacts from well-dated contexts. We report the discovery of a well-dated artifact assemblage containing 14 stemmed projectile points from the Cooper's Ferry site in western North America, dating to ~16,000 years ago. These stemmed points are several thousand years older than Clovis fluted points (~13,000 cal yr B.P.) and are ~2300 years older than stemmed points found previously at the site. These points date to the end of Marine Isotope Stage 2 when glaciers had closed off an interior land route into the Americas. This assemblage includes an array of stemmed projectile points that resemble pre-Jomon Late Upper Paleolithic tools from the northwestern Pacific Rim dating to ~20,000 to 19,000 years ago, leading us to hypothesize that some of the first technological traditions in the Americas may have originated in the region.

An Herbivore-Induced Plant Volatile From Saltcedar (Tamarix spp.) Is Repellent to Diorhabda carinulata (Coleoptera: Chrysomelidae).

The leaf beetle Diorhabda carinulata Desbrochers (Coleoptera: Chrysomelidae) was introduced into the United States in 1999 for classical biological control of the exotic woody invader saltcedar (Tamarix spp. L. [Caryophyllales: Tamaricaceae]). The recent southern expansion of the range of D. carinulata in the United States has precipitated conflict between proponents of biological control of Tamarix and those with concerns over habitat conservation for avian species. Several semiochemicals that mediate aggregations by this species have been reported, but no repellent compounds have been recorded thus far. We now report a repellent compound, 4-oxo-(E)-2-hexenal, induced by adult D. carinulata feeding on saltcedar foliage. Collection of headspace volatiles, gas chromatography mass spectrometry, and electroantennographic analyses identified 4-oxo-(E)-2-hexenal as an insect-induced compound that is antennally active. Behavioral and exposure assays were conducted to test for repellency and toxicity in adults and larvae. Headspace volatiles were also collected from adult males exposed to 4-oxo-(E)-2-hexenal to determine the impact exposure might have on the emission of the aggregation pheromone. 4-Oxo-(E)-2-hexenal elicited electrophysiological responses in adults of both sexes. Behavioral responses indicated repellency across multiple doses for reproductive D. carinulata adults but not in nonreproductive adults. Exposure assays indicated altered behaviors in first instar larvae and adults, but not in third instar larvae. Collection of headspace volatiles indicated that exposure to 4-oxo-(E)-2-hexenal did not alter emission of the D. carinulata aggregation pheromone by adult males. The continued development and field deployment of this repellent compound may provide a new tool for the management of D. carinulata.

Establishing Diorhabda carinulata: Impact of Release Disturbances on Pheromone Emission and Influence of Pheromone Lures on Establishment.

Before weed biocontrol insects are transported and released in a new area, they are commonly collected into small paper containers, chilled, and kept under dark conditions. This process can be termed a pre-release protocol. The influence of a pre-release protocol on establishment success of a gregarious biological control agent was assessed using the northern tamarisk beetle, Diorhabda carinulata (Desbrochers), and its exotic, invasive host plant saltcedar (Tamarix spp.). Pre-release protocol impacts on aggregation pheromone production by D. carinulata were characterized under controlled conditions. Additional experiments were undertaken to determine if deployment of aggregation pheromone lures might enhance the agent's persistence at release sites. Adults that experienced the pre-release protocol produced less aggregation pheromone compared to undisturbed adults. Olfactometer bioassays indicated that a cohort of adults subjected to the pre-release protocol were less attractive to other adults than a control cohort. Efficacy of aggregation pheromone-based lures to retain adults at release sites was evaluated by comparing capture numbers of adult beetles at paired treatment and control release sites, 10-14 days after the release of 300, 500, or 1000 individuals. A greater number of adult D. carinulata were captured where the pheromone lures had been deployed compared to control release sites. Application of aggregation pheromone when a new release of D. carinulata is planned should allow biological control practitioners to increase retention of beetles at a release site.

Field demonstration of a semiochemical treatment that enhances Diorhabda carinulata biological control of Tamarix spp.

The northern tamarisk beetle Diorhabda carinulata (Desbrochers) was approved for release in the United States for classical biological control of a complex of invasive saltcedar species and their hybrids (Tamarix spp.). An aggregation pheromone used by D. carinulata to locate conspecifics is fundamental to colonization and reproductive success. A specialized matrix formulated for controlled release of this aggregation pheromone was developed as a lure to manipulate adult densities in the field. One application of the lure at onset of adult emergence for each generation provided long term attraction and retention of D. carinulata adults on treated Tamarix spp. plants. Treated plants exhibited greater levels of defoliation, dieback and canopy reduction. Application of a single, well-timed aggregation pheromone treatment per generation increased the efficacy of this classical weed biological control agent.

Semiochemicals to enhance herbivory by Diorhabda carinulata aggregations in saltcedar (Tamarix spp.) infestations.

BACKGROUND: Semiochemicals for monitoring, attracting or repelling pest and beneficial organisms are increasingly deployed in agricultural and forest systems for pest management. However, the use of aggregation pheromones and host-plant attractants for the express purpose of increasing the efficacy of classical biological control agents of weeds has not been widely reported. Therefore, we conducted field-based assays to determine if a specialized wax-based matrix impregnated with an aggregation pheromone of the northern tamarisk beetle Diorhabda carinulata (Desbrochers) or host-plant volatiles could increase the efficacy of D. carinulata. RESULTS: The aggregation pheromone and host-plant volatiles were formulated for field application using a wax-based matrix. Reported release rates suggest that this matrix is a viable formulation for enhancing D. carinulata aggregations under field conditions. Pheromone-treated saltcedar plants (Tamarix spp.) not only had higher densities of adult and larval D. carinulata, but also sustained greater levels of foliar damage than control plants. Increased damage from the focused feeding of D. carinulata caused an increase in foliar dieback and decrease in live canopy volume of semiochemical-treated plants. CONCLUSION: Field deployment of these semiochemical formulations could be useful in directing populations of D. carinulata for increased impact on Tamarix spp. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites.

Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species.

Seasonal adaptations to day length in ecotypes of Diorhabda spp. (Coleoptera: Chrysomelidae) inform selection of agents against saltcedars (Tamarix spp.).

Seasonal adaptations to daylength often limit the effective range of insects used in biological control of weeds. The leaf beetle Diorhabda carinulata (Desbrochers) was introduced into North America from Fukang, China (latitude 44° N) to control saltcedars (Tamarix spp.), but failed to establish south of 38° N latitude because of a mismatched critical daylength response for diapause induction. The daylength response caused beetles to enter diapause too early in the season to survive the duration of winter at southern latitudes. Using climate chambers, we characterized the critical daylength response for diapause induction (CDL) in three ecotypes of Diorhabda beetles originating from 36, 38, and 43° N latitudes in Eurasia. In a field experiment, the timing of reproductive diapause and voltinism were compared among ecotypes by rearing the insects on plants in the field. CDL declined with latitude of origin among Diorhabda ecotypes. Moreover, CDL in southern (<39° N latitude) ecotypes was shortened by more than an hour when the insects were reared under a fluctuating 35-15°C thermoperiod than at a constant 25°C. In the northern (>42° N latitude) ecotypes, however, CDL was relatively insensitive to temperature. The southern ecotypes produced up to four generations when reared on plants in the field at sites south of 38° N, whereas northern ecotypes produced only one or two generations. The study reveals latitudinal variation in how Diorhabda ecotypes respond to daylength for diapause induction and how these responses affect insect voltinism across the introduced range.

Host plant quality of Tamarix ramosissima and T. parviflora for three sibling species of the biocontrol insect Diorhabda elongata (Coleoptera: Chrysomelidae).

Several sibling species of the leaf beetle Diorhabda elongata (Brullé) have been introduced into North America for the biocontrol of saltcedars (Tamarix spp.), but only one, D. carinulata (Desbrochers), has been extensively used in the field. The first open releases took place in 2001, and widespread defoliation occurred at sites infested by Tamarix ramosissima, T. chinensis, and their hybrid forms. The beetles failed, however, to establish at sites where other Tamarix species are targeted for control. In this study, we compared the preference and performance of three Diorhabda sibling species using adult choice and larval performance experiments on the two formally targeted Tamarix species: T. ramosissima and T. parviflora. In the adult choice experiment, a greater proportion of D. carinulata was found on T. ramosissima than on T. parviflora. For the other two sibling species, D. elongata (Brullé) and D. carinata (Faldermann), adults were found in similar proportions on the two host plants. In the larval performance experiment, larval growth and survival did not differ between Tamarix species for any Diorhabda type; however, D. carinata larval biomass was 35-50% greater than the other beetles regardless of host species. Based on the few adults of D. carinulata found on T. parviflora in the adult choice experiment, we do not recommend introducing this beetle at sites where T. parviflora is targeted for biological control. The species D. carinata seems especially promising for future release because its larvae gained substantially more biomass than the other beetles during the same time period on both Tamarix species.

Diapause in the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae), a biological control agent for tamarisk (Tamarix spp.).

The tamarisk leaf beetle, Diorhabda elongata Brullé deserticola Chen, was collected in northwestern China and has been released in the western United States to control tamarisk (Tamarix spp.). Characteristics of diapause and reproductive development in D. elongata were examined to improve management as a biocontrol agent. Under long days, 16:8 (L:D) h, males began to emit aggregation pheromone within 2-3 d of adult emergence, mating occurred, and females oviposited within 7 d of adult emergence. Under short days, 12:12 (L:D) h, males did not emit pheromone, mating did not occur, and both males and females entered reproductive diapause marked by inconspicuous gonads and hypertrophied fat body. Ovaries of diapausing females lacked vitellogenic oocytes, and the ovarioles were clear and narrow, whereas reproductive females had enlarged ovaries with two to three yellow oocytes per ovariole. Diapausing males had thin, transparent accessory glands and ejaculatory ducts, whereas reproductive males had thick white accessory glands and white opaque ejaculatory ducts. Sensitivity to diapause-inducing photoperiods extended into the adult stage. Reproductive females ceased oviposition, resorbed oocytes, and entered diapause when switched from long to short days. Diapause-destined insects ceased feeding and entered the leaf litter 10-20 d after adult emergence, whereas reproductive insects remained on the plants and fed for at least 30 d. Reproductive insects exhibited dispersal behaviors, such as attempted flights, whereas diapause-destined insects did not show dispersal behaviors. Information gained from these studies will be used to better manage populations in the field and to improve rearing and storage in the laboratory.

Seasonal timing of diapause induction limits the effective range of Diorhabda elongata deserticola (Coleoptera: Chrysomelidae) as a biological control agent for tamarisk (Tamarix spp.).

The leaf beetle Diorhabda elongata Brullé subspecies deserticola Chen, collected in northwestern China, has been released in the western United States to control tamarisk (Tamarix spp.). While beetle establishment and saltcedar defoliation have been noted at northern study sites, this species has not established at latitudes south of the 38th parallel. Critical daylength for diapause induction was measured in the laboratory and ranged between 14 h 50 min to 15 h 08 min, depending on temperature, and adults were shown to cease reproduction and enter diapause at daylengths of 14 h 30 min or less. Critical daylength in the field was measured at approximately 14 h 39 min and occurred 13 d before 50% of the population reached diapause. South of 36 degrees 20' N, the longest days of the year are shorter than 14 h 39 min, making the beetles univoltine in the southern United States. North of 36 degrees 20' N, a window of reproductive activity opens 13 d after the critical daylength is reached in the spring and closes 13 d after it is passed in the summer, allowing at least a partial second summer generation. It is predicted that south of the 38th parallel, premature diapause will increase mortality and disrupt synchrony between the life cycle of the beetle and host plant availability. This could hinder establishment and help explain the failure of this population south of the 38th parallel, providing a rationale for testing other populations of D. elongata in the southern range of Tamarix in North America.

Behaviorally active green leaf volatiles for monitoring the leaf beetle, Diorhabda elongata, a biocontrol agent of saltcedar, Tamarix spp.

Biological activity and chemistry of host plant volatiles were investigated for Diorhabda elongata, Brullé (Coleoptera: Chrysomelidae), a biological control agent for the invasive tree, saltcedar (Tamarix spp., Tamaricaceae). Gas chromatographic-electroantennographic detection (GC-EAD) analysis of volatiles collected from adult D. elongata feeding on saltcedar foliage or from saltcedar foliage alone showed 15 antennally active compounds. These compounds were more abundant in collections from beetle-infested foliage. Antennally active compounds were identified by GC-mass spectrometry (MS) and confirmed with authentic standards. The emissions of the most abundant GC-EAD-active compounds, green leaf volatiles (GLV), were quantitated by GC-MS. A blend of four GLV compounds, mimicking the natural blend ratio, was highly attractive to male and female D. elongata in the field, and a combination of GLV and male-produced aggregation pheromone attracted significantly greater numbers of D. elongata than did either bait alone. A preliminary experiment with a blend of seven additional GC-EAD-active saltcedar volatiles did not show any behavioral activity. The combination of the pheromone and the green leaf odor blend could be a useful attractant in detecting the presence of the biocontrol agent, D. elongata, in stands of saltcedar newly colonized by the beetle.

The aggregation pheromone of Diorhabda elongata, a biological control agent of saltcedar (Tamarix spp.): identification of two behaviorally active components.

The leaf beetle Diorhabda elongata Brullé (Coleoptera: Chrysomelidae) has been introduced as a biological control agent for saltcedars, Tamarix spp., an exotic, invasive weedy tree in the western United State. Gas chromatographic (GC) analysis of volatiles collected from feeding male or female beetles, or saltcedar foliage alone, showed two components produced almost exclusively by males. These compounds elicited responses from antennae of male and female beetles in GC-electroantennographic detection (EAD) analyses. The compounds were identified as (2E,4Z)-2,4-heptadienal (1) and (2E,4Z)-2,4-heptadien-1-ol (2) by GC-mass spectrometry (MS), and confirmed with authentic standards. The two compounds were also detected at trace levels from feeding females and foliage controls, but the amounts from feeding males were 8-40 times higher, typically 55-125 ng per day per male. The amounts of 1 and 2 in collections from females did not differ significantly from amounts collected from control foliage. In field trials, 2 as a single component was as attractive as a 1:1 blend of 1 and 2. Compound 1 as a single component was more attractive than controls, but much less attractive than 2 or the blend. Males and females were attracted in about equal numbers, indicating that this is an aggregation pheromone.