Exotic Pest Plant Research Articles

Ultra-deep sequencing of 45S rDNA to discern intragenomic diversity in three Chrysodeixis species for molecular identification

Species identification is necessary to prevent introductions of exotic plant pests through global trade. Many of these pests are understudied and lack publicly available DNA sequence data on which rapid molecular identification methods can be based. One such lineage is the genus Chrysodeixis, which includes three species of potential concern for United States trade initiatives: C. includens, C. chalcites, and C. eriosoma. Here we describe a method to generate robust 45S rDNA profiles using long read sequencing in order to clarify evolutionary relationships and develop a real-time PCR identification technique. Such an identification tool will be useful in rapidly differentiating between Chrysodeixis species of quarantine concern where traditional morphological identification methods are insufficient. Molecular methods such as this greatly reduce the time spent identifying each specimen, allow for detection of eDNA, vastly increase throughput, and increase the probability of detection. The methods presented here will be generally adaptable to any understudied lepidopteran taxa that necessitates a molecular diagnostic assay and, with adjustment or testing of the primers, could be applied to any group for which development of rDNA profiles in a benchtop setting would prove useful.

Taxonomic, geographic, and diversity trends for exotic plant pests in recent biosurveillance articles

Taxonomic, geographic, and diversity trends for exotic plant pests in recent biosurveillance articles

Napiergrass: Biology and Control in Sugarcane

Napiergrass (Pennisetum purpureum Schumacher) is an enormous, weedy, cane-like grass (Figure 1) commonly seen growing along canals and roadsides in the sugarcane production area of south Florida. Napiergrass, also known as elephantgrass, has been documented in almost 30 counties throughout Florida. It is of African origin, but has been introduced to all tropical areas of the world because of its ability to quickly produce large amounts of biomass. Currently, napiergrass is widely used in Central America, South America, and Africa as a forage crop. Napiergrass was introduced to South Florida and Texas for use as a forage crop, but it is no longer widely used for this purpose and has become a major weed problem. Napiergrass is now established throughout southern Florida, especially along canal and ditch banks and in disturbed or cultivated areas. Because of the weedy characteristics of napiergrass, it is considered to be one of the world's worst weeds and has been listed as an invasive species by the Florida Exotic Pest Plant Council. Although it can be found in central and northern Florida, it is less common due to cooler temperatures. This document is SS-AGR-242, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date: July 2005. Reviewed October 2008. 
 SS-AGR-242/SC071: Napiergrass: Biology and Control in Sugarcane (ufl.edu)

Overview of exotic pest and disease notifications 2015-2017


 
 
 Early detection of newly arrived exotic plant pests and diseases is critical to protect New Zealand’s environment and agriculture. For that purpose, the Ministry for Primary Industries (MPI) conducts active surveillance of numerous high risk organisms, such as fruit ies or gypsy moth, via speci c targeted surveillance programmes.
 In addition, MPI utilises passive surveillance to enable early detection and reporting of exotic pests and diseases. Members of the public, industry groups, plant health professionals, and diagnostic laboratories report detections of suspected exotic pests and diseases via the “exotic pest and disease hotline” (0800 80 99 66), which operates 24 hours a day, 7 days a week. Noti cations are promptly investigated by MPI and deduced biosecurity risks can thus be addressed using appropriate containment, eradication, or long-term management measures.
 An overview of passive surveillance data (2015—2017) is presented, with the focus on noti cations and investigations of exotic plant pests and diseases associated with recently imported goods. Particular attention is given to cases dealing with high-risk organisms such as the brown marmorated stink bug (BMSB).
 
 

Can grain growers and agronomists identify common leaf diseases and biosecurity threats in grain crops? An Australian example

The Australian grains industry relies upon growers and agronomists to be aware of pests and diseases in their crops and to notify their local State Department of Agriculture when they suspect an incursion of a high priority pest (HPP). This raises the question “Are growers and agronomists, within the Australian grains industry, able to meet this expectation?” A training needs analysis was undertaken to determine the capacity of growers and agronomists to identify three endemic diseases (powdery mildew in barley, stripe rust in wheat and blackleg in canola) in their crops. Their knowledge of the top four-biosecurity threats to the Australian grains industry (Karnal bunt, Khapra beetle, barley stripe rust and Russian wheat aphid) was also determined. Benchmarks for successfully identifying these diseases were set beforehand at 70% of growers and 80% of agronomists; participants’ ability to identify these endemic diseases in crops met these benchmarks. However, their ability to recognise blackleg in canola was significantly lower than for the two cereal foliar diseases. There was a significant correlation of region with these capabilities, with a greater proportion of participants in Western Australia (WA) recognising powdery mildew in barley than in Eastern Australia (EA). In contrast, a greater proportion of participants in EA were able to identify stripe rust of wheat than in WA. The education levels of participants corresponded with their ability to identify blackleg in canola. Participants’ knowledge and awareness of symptoms and signs associated with the top four biosecurity threats were well below expectations; fewer than half of the participants answered questions on these four HPPs. Gender, age and educational level did not correlate with the participants’ knowledge and awareness of the four HPPs with the exception of Karnal bunt. Participants with a higher level of education had significantly more knowledge of symptoms associated with Karnal bunt than did participants with lower levels of education. The use of diagnostic services by the grains industry participants is a vital component of general surveillance. This survey showed that use of these services by growers was significantly lower than by agronomists. Awareness of the National Exotic Plant Pest Hotline and GrainGuard was significantly lower than other diagnostic services for both growers and agronomists. Diagnostic services need to be promoted further to increase awareness and use by growers and agronomists. Correct diagnosis of disease and pest symptoms is vital for the biosecurity of the grains industry.

Biosecurity and food security—effective mechanisms for public-private partnerships

Maintaining Australia’s status as a major food exporter requires ongoing protection of its cropping industries from exotic pests and diseases. The number of pests classified as high priority threats to Australia’s plant industries now stands at over 300 (Plant Health Australia Annual Report 2014). It is often stated that Australia’s geographic isolation provides a natural barrier from many exotic pests that could damage plant production industries and the unique natural environment. Isolation, however, is not enough given that pests can enter through natural means or by being brought into the country with the increasing movements of people and goods. In an increasingly globalised world economy, Australia relies on a rigorous biosecurity system operated in partnership between governments and industry to mitigate risks from exotic pests. Steadily increasing trade volumes and passenger travel, global movements of serious pests, particularly into neighbouring countries, and the emergence of new and variant species of pests, will continue to test already stretched biosecurity capabilities. Plant Health Australia (PHA) provides the centrepiece of a unique system that manages the national preparedness and response for exotic plant pest incursions in Australia. PHA is a public company that facilitates decision making and funding for effective responses to emergency plant pests. PHA also independently advocates and adds value to, Australia’s national biosecurity system. Utilising the Emergency Plant Pest Response Deed (EPPRD), a legal agreement that brings together governments and industries in formal response arrangements, PHA ensures that national incursion responses are timely, science based, transparent and effective, with the aim of maintaining supply of quality clean food.

Evaluation of Control of Napiergrass (Pennisetum purpureum) with Tillage and Herbicides

AbstractNapiergrass has potential as a cellulosic biofuel crop because of its rapid growth habit in the southern United States. However, it is also listed as a potential invasive species by the Florida Exotic Pest Plant Council. For field renovation, information about napiergrass control in response to tillage and herbicides is required. Field studies were initiated to evaluate control of napiergrass established in fields for over 3 yr at Plains, GA, and Tifton, GA. For tillage and POST herbicides, imazapyr plus glyphosate consistently controlled napiergrass relative to diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage in terms of visual injury, stem height and dry biomass reduction. One application of imazapyr plus glyphosate controlled napiergrass 74 and 94%, and reduced plant stem height to 6 and 15% of the nontreated control. When diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage was used alone with no sequential herbicides, napiergrass control ranged from 12 to 33%; when these control tactics were followed by two sequential applications of either sethoxydim or glyphosate, napiergrass control varied from 45 to 99%. Reductions in plant heights were reflective of injury 47 d after final herbicide applications (May/June). Napiergrass yield in dry biomass production was reduced by imazapyr plus glyphosate ≥ 86% relative to the nontreated control (NTC). Diclosulam plus glyphosate, sulfentrazone plus glyphosate, or tillage alone was not effective in reducing napiergrass dry biomass yields ranging from 1 to 47% compared with the NTC; when these treatments were followed by sequential applications of sethoxydim or glyphosate, napiergrass dry biomass was reduced 46 to 91% compared with the NTC. Tillage plus two applications of sethoxydim or glyphosate exhibited control potential because they provided levels of napiergrass control similar to imazapyr-based treatments. Tillage plus multiple applications of sethoxydim or glyphosate offers flexibility to crop rotations as compared with the residual herbicide imazapyr, which has many crop rotation restrictions because of carryover concerns.

PestLens: an early‐warning system supporting U.S. safeguarding against exotic plant pests

The effectiveness of safeguarding and quarantine actions aimed at preventing the introduction and minimizing the impact of exotic plant pests relies on current information about those pests. National Plant Protection Organizations (NPPOs) face the following challenges: staying up to date on continuously emerging new pest information, filtering and evaluating this information, disseminating it effectively and efficiently, applying it toward decision making, and coordinating and tracking the resulting decisions and safeguarding actions. PestLens, the web‐based early‐warning system of the NPPO of the United States, is designed to address all of these challenges. This paper describes the PestLens system and discusses lessons learned during system development and operation.

Managing Mexican Petunia (Ruellia simplex C. Wright) in the Home Landscape

Environmental tolerance, abundant seed production, and an ability to easily grow from plant stem sections have allowed Mexican petunia to spread into natural areas that border urban areas. The Florida Exotic Pest Plant Council lists Mexican petunia (wild-type and non-sterile cultivars) as a Category 1 invasive species, meaning that it is “altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives.” These potential changes to community structure and ecological function are of particular concern in Florida wetlands, where changes to plant communities have the potential to impact not just plant-animal interactions, but also overall hydrology on a whole watershed level. This 6-page fact sheet was written by C. A. Reinhardt Adams, C. Wiese, L.C. Lee, S.B. Wilson, A. M. Smith, and R. Freyre, and published by the UF Department of Environmental Horticulture, April 2014.

An overview of exotic plant pest and disease surveillance 2011 2014

Active and passive surveillance form the backbone of New Zealands early pest and disease detection system and provide evidence about pest or disease status to support growing and maintaining export markets and trade for plant products Effective surveillance increases the number of options available to emergency management teams to manage new biosecurity risks from eradication and containment to pest management An overview of 3 years of plant pest and disease surveillance data is presented including an update of the surveillance system and potential areas for development The importance of increasing awareness by Intermediaries (a group that includes scientists crop scouts and biosecurity staff) of the Ministry for Primary Industries exotic pest and disease hotline (0800 80 99 66) to enable early risk management is highlighted

Natural Area Weeds: Old World Climbing Fern (Lygodium microphyllum)

Native to Africa, Asia, and Australia, Old World climbing fern (OWCF) is a newcomer to Florida that has spread at an alarming rate since its introduction. The Florida Exotic Pest Plant Council considers Old World climbing fern to be invasive. It’s also regulated by laws of the Florida Department of Agriculture and Consumer Services (FDACS) as a Florida Noxious Weed and by the United States Department of Agriculture (USDA) as a Federal Noxious Weed. It may be the most serious threat to Florida’s natural areas. This 6-page fact sheet was written by Kenneth A. Langeland and Jeffery Hutchinson, and published by the UF Department of Agronomy, February 2013.
 http://edis.ifas.ufl.edu/ag122

Natural Area Weeds: Skunkvine (Paederia foetida)

Native to eastern and southern Asia, skunkvine is an invasive plant species introduced to the USDA Field Station near Brooksville before 1897. It has been included on the Florida Exotic Pest Plant Council List of Invasive Species as a Category I, defined as “species that are invading and disrupting native plant communities in Florida.” It was added to the Florida Noxious Weed List in 1999, making it illegal to possess, move, or release in Florida. This 3-page fact sheet was written by K. A. Langeland, R. K. Stocker, and D. M. Brazis, and published by the UF Department of Agronomy, February 2013. 
 http://edis.ifas.ufl.edu/wg208

A suite of models to support the quantitative assessment of spread in pest risk analysis.

Pest Risk Analyses (PRAs) are conducted worldwide to decide whether and how exotic plant pests should be regulated to prevent invasion. There is an increasing demand for science-based risk mapping in PRA. Spread plays a key role in determining the potential distribution of pests, but there is no suitable spread modelling tool available for pest risk analysts. Existing models are species specific, biologically and technically complex, and data hungry. Here we present a set of four simple and generic spread models that can be parameterised with limited data. Simulations with these models generate maps of the potential expansion of an invasive species at continental scale. The models have one to three biological parameters. They differ in whether they treat spatial processes implicitly or explicitly, and in whether they consider pest density or pest presence/absence only. The four models represent four complementary perspectives on the process of invasion and, because they have different initial conditions, they can be considered as alternative scenarios. All models take into account habitat distribution and climate. We present an application of each of the four models to the western corn rootworm, Diabrotica virgifera virgifera, using historic data on its spread in Europe. Further tests as proof of concept were conducted with a broad range of taxa (insects, nematodes, plants, and plant pathogens). Pest risk analysts, the intended model users, found the model outputs to be generally credible and useful. The estimation of parameters from data requires insights into population dynamics theory, and this requires guidance. If used appropriately, these generic spread models provide a transparent and objective tool for evaluating the potential spread of pests in PRAs. Further work is needed to validate models, build familiarity in the user community and create a database of species parameters to help realize their potential in PRA practice.

CHARACTERIZING THE INVASIVE POTENTIAL OF ORNAMENTAL PLANTS

The substantial economic and ecological costs of invasive plant management and removal warrant aggressive eradication and prevention programs. Ornamental horticulture has been recognized as the fastest growing segment of U.S. Agriculture, as well as the main source of plant invasions worldwide. Florida ranks second among U.S. states in the degree of ecosystem devastation as a result of exotic invasive species. Cultivated or improved forms of a number of the ornamental species listed as invasive by Florida’s Exotic Pest Plant Council have been selected for their attractive flower color, plant form, foliage, drought tolerance, or cold hardiness. As the cultivars are generally propagated vegetatively, relatively little is known about their pollination biology, seed production, seed viability and growth rate under varying conditions. To identify safe alternatives to ornamental invasives, researchers at the University of Florida have evaluated numerous cultivars of Mexican petunia (Ruellia tweediana), privet (Ligustrum spp.), fountain grass (Pennisetum spp.), porterweed (Stachytarpheta spp.), heavenly bamboo (Nandina domestica), and lantana (Lantana camara). These species are not only problematic in Florida, but highly invasive in other parts of the world. Research efforts are underway to identify and evaluate sterile non-invasive forms of lantana, heavenly bamboo, and Mexican petunia.

Biosecure packaging for the transport of diagnostic samples

For the transport of diagnostic samples, particularly suspected exotic plant pests, a triple packaging system ensured integrity was maintained and the sample arrived in good condition for diagnosis. The type of sample determined the packaging combinations best suited for the primary, secondary and triple (outer) layers. Packaging suitable for all layers included inexpensive bags and boxes available from supermarkets, Australia Post and commercial packaging suppliers. Press seal bags and small screw top containers were effective primary and secondary packaging for most samples and padded bags or corrugated cardboard boxes for the tertiary package. Samples that could leak required an absorbent sponge in the secondary layer and some samples require pre-packaging to ensure protection before being placed in the primary package. Samples packed in boxes required padding to minimise movement during transport. There was no difference in package integrity between samples sent via couriers and Australia Post.

Emergency response to the incursion of an exotic myrtaceous rust in Australia

In April 2010, an exotic rust of Myrtaceae was detected in New South Wales, Australia, identified as Uredo rangelii and provided a new common name, ‘myrtle rust’. It was declared an Exotic Plant Pest as it was recognised as a taxon within the Puccinia psidii (eucalyptus/guava rust) complex, which is a key biosecurity threat to Australia. This paper describes the emergency response that ensued, including surveillance, tracing, quarantine, destruction and community engagement. A unique aspect of this emergency response was the disjointed stages of action, with the response initially falling under national emergency management procedures (PLANTPLAN) for 1 week (Stage I), then outside the national process and under the state process for a further 2 months (Stage II), before falling again under the national emergency response program (Stage III). Problems associated with the identity of the introduced rust are discussed, and a brief update on the current status of the rust, now established in Australia, is provided, including distribution and impact in the native environment and affected industries. Major outcomes of recent reviews of the emergency response are outlined.

Risk maps for targeting exotic plant pest detection programs in the United States

In the United States, pest risk maps are used by the Cooperative Agricultural Pest Survey for spatial and temporal targeting of exotic plant pest detection programs. Methods are described to create standardized host distribution, climate and pathway risk maps for the top nationally ranked exotic pest targets. Two examples are provided to illustrate the risk mapping process: late wilt of corn (Harpophora maydis) and the giant African land snail (Achatina fulica). Host risk maps were made from county‐level crop census and USDA Forest Inventory and Analysis data, respectively. Climate risk maps were made using the North Carolina State University–USDA APHIS Plant Pest Forecasting System (NAPPFAST), which uses a web‐based graphical user interface to link climatic and geographic databases with interactive templates for biological modelling. Pathway risk maps were made using freight flow allocation data sets to move commodities from 7 world regions to 3162 US urban areas. A new aggregation technique based on the Pareto dominance principle was used to integrate maps of host abundance, climate and pathway risks into a single decision support product. The maps are publicly available online (http://www.nappfast.org). Key recommendations to improve the risk maps and their delivery systems are discussed.

Using genetic and morphological analysis to distinguish endangered taxa from their hybrids with the cultivated exotic pest plant Lantana strigocamara (syn: Lantana camara)

Because highly invasive species can rapidly assimilate rare taxa, we questioned whether two Florida endangered Lantana depressa varieties existed 21 years after Sanders documented their widespread hybridization with exotic Lantana strigocamara, and whether morphological traits could accurately discriminate genetic individuals. Stepwise discriminant analysis of morphological characters discriminated the three taxa, correctly classifying 98, 91, 89% of L. strigocamara, L. depressa var. depressa, and var. floridana. Hybrids blurred taxonomic distinctions of varieties and reduced classification accuracy by 7–17%. Species-specific Random Fragment Length Polymorphism (RFLP-PCR) confirmed hybridization has occurred. Intersimple Sequence Repeat (ISSR) fingerprints analyzed with STRUCTURE identified three groups indicating introgression. Morphological traits significantly, but weakly correlated with q ratios (P = 0.0001; r 2 = 0.45). Although L. strigocamara introgression is widespread and ongoing, wild populations contain individuals that are predominantly L. depressa genome, supporting actions to remove adventive L. strigocamara, prevent its sale, and promote sales of genetically confirmed natives.

Hierarchical Bayesian modelling of early detection surveillance for plant pest invasions

Early detection surveillance programs aim to find invasions of exotic plant pests and diseases before they are too widespread to eradicate. However, the value of these programs can be difficult to justify when no positive detections are made. To demonstrate the value of pest absence information provided by these programs, we use a hierarchical Bayesian framework to model estimates of incursion extent with and without surveillance. A model for the latent invasion process provides the baseline against which surveillance data are assessed. Ecological knowledge and pest management criteria are introduced into the model using informative priors for invasion parameters. Observation models assimilate information from spatio-temporal presence/absence data to accommodate imperfect detection and generate posterior estimates of pest extent. When applied to an early detection program operating in Queensland, Australia, the framework demonstrates that this typical surveillance regime provides a modest reduction in the estimate that a surveyed district is infested. More importantly, the model suggests that early detection surveillance programs can provide a dramatic reduction in the putative area of incursion and therefore offer a substantial benefit to incursion management. By mapping spatial estimates of the point probability of infestation, the model identifies where future surveillance resources can be most effectively deployed.

Tropical Spiderwort (Commelina benghalensis L.) Increases Growth under Elevated Atmospheric Carbon Dioxide

Although considerable effort is being spent studying exotic plant pests, little consideration has been given as to how invasive plants might react to the increasing concentration of CO(2) in the atmosphere. Tropical spiderwort (Commelina benghalensis L.) is considered one the world's worst weeds and is becoming more of a problem in agricultural settings of the southeastern USA. Growth responses of tropical spiderwort were evaluated using plants grown in containers with a soilless potting medium under ambient and elevated (ambient + 200 mumol mol(-)(1)) levels of CO(2) in open-top field chambers. Although plant height was unaffected by CO(2), leaf and flower number tended to increase (approximately 23%) when exposed to elevated CO(2). Aboveground plant parts exhibited significant increases in dry weight when exposed to high CO(2); leaf, flower, stem, and total shoot dry weights were increased by 36, 30, 48, and 44%, respectively. Total plant dry weight was increased by 41% for plants grown under high CO(2). Root dry weight and root length were unaffected by CO(2) concentration. Tropical spiderwort allocated more biomass to stems and tended to allocate less to roots when plants were exposed to high CO(2). Plant carbon concentration and content tended to be higher in CO(2)-enriched plants, whereas plant nitrogen concentration tended to be lower; thus, elevated CO(2)-grown plants had higher C/N ratios. Also, the amount of biomass produced per unit nitrogen was higher for plants exposed to elevated CO(2). The growth response of this plant is in the upper range typical for C3 plants.