Final Exam Flashcards
Lingering ash
a subset of ash trees that stayed healthy with little change in numbers over time even as majority of others declined into death.
–shows that some trees may have some genetic resistance
-hope to keep in forest to produce seeds—prolonging spp presence in environment
What steps were required for EAB biocontrol agents to be established?
-Step 1: finding the Biocontrol Agents
-Step 2: Release and Establishment
-Step 3: Testing Impacts & Efficacy
What are the options for dealing with ash trees infected with EAB?
1) tree removal (for those already infected/stressed)
2) insecticide injections (“bottom-up” tree defense approach)—largely done in urban areas for high-value trees, not feasible in larger numbers, laborous & costly
3) biological control (“top-down” predatory approach)—self sustaining once established
How are effects of EAB biocontrols surveyed for?
yellow pan traps, sentinel logs (for areas where mature trees are largely dead, only saplings)
What three forest types were studied for EAB biocontrol efficacy?
-early invasion forest (healthy mature trees & saplings not heavily infested yet)
-post invasion forest (mature trees largely dead, only saplings)
-urban environments (more isolated street trees)
Results of EAB Biocontrol Studies & looking ahead—what do we hope occurs?
1) parasitoids establish populations in all 3 forest types
2) parasitoids disperse to new locations
3) EAB populations are suppressed
4) subset of trees remain healthy
5) regeneration?
-though mature trees die, hopefully EAB pops decline in short-term, biocontrols can better manage them; some lingering ash live on and reproduce, saplings are able to grow into mature trees—hopefully EAB populations decline and ash spp can survive.
Centrifugal Phylogenetic Method
testing specificity of biocontrol and potential impacts on non-target species—including closely related native spp; moving out to more distantly related spp; species of agricultural or economic importance; and threatened / endangered spp (50+ spp used, often close to 100)
*uses choice (bouquet of options including target) AND no choice tests (either eat plant spp or die)
What are some examples of successful biocontrol projects?
biocontrol of St. Johnswort: now considered an uncommon roadside weed in California (beetle)
biocontrol of Cassava Mealy Bug (CMB): parasitoid wasp introduced to 30+ countries–greatly successful
biocontrol of prickly pear cactus (in Australia, some other countries)
Why is Prickly Pear Cactus biocontrol causing issues now after 80-90 years of success?
also introduced Cactoblastis caterpillars in Caribbean to control native cacti spp (due to overgrazing of pastures so cacti would be remnant)—appeared in Florida Keys, which have federally endangered native Opuntia cacti spp. Moved all through Florida, now in Georgia and S Carolina, west to Louisiana, then jumped into SW Texas in 2018. NOW HAVE A PATHWAY DOWN INTO MEXICO (where most diversity of Opuntia cacti spp are). 2009—eradicated population by releasing infertile males.
–now found a parasitoid wasp in native range to try and eradicate TX population—getting close to possible release
Whose article ignited a contentious debate in the 1980s over biocontrol use?
Francis Howarth article on non-target effects of biocontrols. Highlighted mostly examples of biocontrols that would never be released today (projects before rules put in place).
-ex: Kane toads, other generalist predators, rosy wolf snail
How safe is Classical Biological Control?
-for control of plants—it is generally very safe (plant feeding insects tend to have relatively restricted host ranges)
-for other types of biocontrol—worst examples have been generalist predators that would never be repeated for release. HOWEVER-host/prey range testing for biocontrol of non-plant organisms are not nearly as well developed (ex: just a couple decades ago, would only test specificity to the family level for insects, now more to genus or even species level)
-absence of evidence is not necessarily evidence of absence in respect to non-target effects
-HOWEVER, NEED TO EVALUATE THE RISK OF INTRODUCTION RELATIVE TO THE RISK OF DOING NOTHING
Resistance Breeding
-traditional breeding identifies genotypes with resistance followed by selective breeding and propagation
-also molecular approaches: may shortcut/overcome limitations of traditional breeding
-also used in natural ecosystems (ex: pines resistant to blister rust; lingering ash; etc)
sterile male genetic biocontrol
irradiated males rendered sterile, propagated and released to compete with wild males (ex: sea lampreys)
Trojan male genetic biocontrol
feminization produced through sex-reversal by hormone treatment. Compete with wild females
Trojan female genetic biocontrol
steady release of females that carry mitochondrial DNA mutations that cause reduction to male, but not female fertility
Gene drives
using CRISPR/Cas9 for gene editing enables synthetic gene drives that in theory could be adapted for use in any sexually reproducing spp
—none are used or approved yet in nature but large-scale studies ongoing for vector mosquitos and invasive agricultural insect pests, rodents on remote islands, etc
(ex: Cornell looked at diamondback moth in field of cabbage with no containment…)
*many ethical concerns have been raised:
-what if edited genes made it back to native range?
Potential effects of climate change on invasives:
1) altered vectors / pathways
Ex: once Arctic sea stops having ice for decent periods of time during year, trade ships may start to travel through Arctic instead to save on time/fuel
2) altered climatic constraints (allows new invasives)
Ex: Florida is gaining more invasions of tropical spp that previously would not have survived
3) altered distribution of existing invasive spp
Ex: spp able to move farther north/to higher elevations
4) altered impact of existing invasive spp
Ex: increase in CO2 can increase biomass of invasive plants—also makes them less nutritious for herbivores; herbicides may become less effective as well
5) altered effectiveness of management strategies for invasive spp
Ex: biocontrol release options may no longer work as effectively (as biocontrol agents are no longer inside of their ideal climate envelope)
Examples of changing insect/animal phenology:
-ex: Fall webworm in eastern Asia—shifted from bivoltine (2-gen) to trivoltine (3-gen) development per year at lower latitudes 40 yrs after introduction to Japan—3-gen are much more destructive than the 2-gen
-ex: spongy moth—has been very well-studied, have clear quantitative assessment of changes in range. There has been expansion in Northern areas (MN), but contraction in southeast (VA, NC coastal plain). Thought that exposure to supraoptimal temps reduces fecundity and survival
What are some major reasons for and implications of mosquito invasions with climate change?
Container breeders Aedes egypti (yellow fever mosquito) and A. albopictus (Asian tiger mosquito)
—Asian tiger mosquito is easily moved and is quickly replacing yellow fever mosquito. Many viruses are evolving to better use tiger mosquitos as vector
*predicted to quickly spread range throughout US—already in NJ and Long Island
*largely moved with old tire piles (tires burned to make cement) as well as lucky bamboo plants in CA
—COMPOUND INVASION PROBLEM
-humans are increasingly mobile; concentrated in urban areas; our transformation of ecosystems aids mosquitos…
-viruses changing ranges, hosts, transmission, physiology, evolution
-efficient transport modes and pathways
Once eradication has failed, options come down to…
do nothing or manage in perpetuity
*The only (current) way around this dilemma on a large scale is successful biological control.
–Other possible future options:
Breeding genetic resistance and gene drives
Compare 2 control strategies available after eradication fails:
(1) Control (Suppression) – reduce population below some defined level to reduce negative
economic and/or ecological effects: Manage the species where it already occurs.
* Physical/Mechanical
* Chemical
* Biological
* Technological (transgenics, gene drives
(2) Exclusion / Containment: Prevent or slow further expansion of the species beyond its
current range
* Barriers (physical) to prevent movement
* Eradication of incipient populations beyond established area
* Quarantines - Different levels - Local, regional, international
* Limit/prevent movement of vectors associated with a species
Integrated Pest Management (IPM)
is a synthetic approach to managing invasive species, adopted from pest management in agricultural systems. With respect to invasive species, IPM programs utilize a suite of different tactics simultaneously. This can be in different parts of the invasive range or within the same area using different tools.
*Successful IPM programs often involve an array of methods such as herbicides, education, biocontrol, spot
eradication, etc.
What is SLAM IPM Program?
*SLow Ash Mortality (adopted from spongy moth program)
- Reduce ash phloem on the landscape to levels that make it more difficult for EAB to
produce large numbers of offspring - Strict firewood regs / and log movement
- Eradicate outlier populations where possible
- In urban areas, remove low value ash street trees and replace with other species,
protect high value trees with injectable systemic pesticide. - Introduce biological control agents
Describe Brown Tree Snake Program in Guam
likely introduced as a stowaway on US military
equipment. Has caused the extinction of multiple bird and herp species. Focus is on preventing spread to other islands.
*Modes of containment:
* Canine Detection: Guam & Oahu. Beagles inspect all air cargo
* Habitat Modification: Forested areas completely removed around cargo /
transportation handling facilities
* Physical Barriers: At Guam’s seaport, 22.5 ha enclosed within vinyl and smooth concrete
* Trapping: Cone traps baited with a mouse or a gecko
* Deployment of Tylenol baited mice in forest canopy. (Tylenol is fatal to snakes)
* Visual Perimeter Surveillance: At night, spotting lamps used around airport
perimeters.
* Biocontrol - USDA evaluating potential biocontrols including a fatal respiratory virus specific to snakes (no native snakes on Guam)
