Trivial movements and redistribution of polyphagous insect herbivores in heterogeneous vegetation

The aim of this thesis was to study the interplay between movement patterns of polyphagous insect herbivores and vegetation heterogeneity within agricultural fields. I examined if and how 1) host plant species, 2) host plant quality, 3) vegetation architecture, and 4) trap crop physical design influence movement patterns of individuals and spatial distribution of populations. Foragers may aggregate in profitable areas by tactic movement, or by area-restricted search, i.e. by moving randomly but slowing down movement and increasing rate of turning after encountering a profitable patch. Movement patterns of polyphagous herbivores have a high potential for influencing their distribution among hosts differing in quality. However, information on the role random vs. non-random components in their movement behavior is scarce. The results of this thesis show that both host plant species and within species differences in host plant quality affect movement behavior of a polyphagous herbivore, the European tarnished plant bug nymphs. The host plant induced movement patterns also explained the distribution of nymphs in heterogeneous vegetation. Because redistribution was very fast, it appears that no tactic behavior is needed for the nymphs to locate preferred hosts in heterogeneous vegetation composed of small patches. Instead the nymphs may successfully locate superior hosts merely by random movement coupled with sensitivity to local host quality. The physical structure of environment influences redistribution of populations at several spatial scales. At small scale the architecture of vegetation may influence redistribution of insects that move on the plant surface. At large scale e.g. trap crop physical design may affect redistribution of pests. In this thesis I derive a model for predicting the impact of vegetation architecture on the rate of displacement by insects moving on the plant surface. I also present and explore models of the interplay between pest movement and trap crop physical design. The trap crop models suggest that considerable reduction in pest density may be achieved using small trap crop cover with trap crops that the pest distinctly prefers over the crop. It supports also the idea that trap crop placement may have a dramatic impact on the efficiency of the trap crops

Pest Risk Assessment for Dutch elm disease

Dutch elm disease (DED) is a fungal disease that causes high mortality of elms. DED and its vector beetles are widely present in most of the countries in the Northern Hemisphere, but they are not known to be present in Finland. DED is a major risk to plant health in Finland. DED and its vectors are moderately likely to enter Finland by natural spread aided by hitchhiking, because they are present in areas close to Finland. Entry via other pathways is much less likely, mainly due to the low volume of trade of untreated wood and plants for planting. DED and its vectors could likely establish in the southern parts of the country, since they currently occur in similar climatic conditions in other countries. DED could cause massive environmental damage as natural elm groves are critically endangered habitats in Finland. The economic consequences to the owners of mature elms could also be significant. Eradication or containment of DED could be possible if strict measures were taken as the patchy distribution of elms would limit the spread of the disease. The most important source of uncertainty in this assessment is the lack of information regarding the amount of elm in fuel wood, wood waste and wood chips imported to Finland

Mapping risks of pest invasions based on the spatio-temporal distribution of hosts

Surveying multiple invasive pest species at the same time can help reduce the cost of detecting new pest invasions. In this paper, we describe a new method for mapping the relative likelihood of pest invasion via plant propagation material in a geographic setting. The method simulates the invasion of a range of pest species, including arrival in an uninvaded area, spread, and survival in a novel landscape, using information on the spatial and temporal distribution of the suitable host crop species and tentative knowledge of the spread and survival capacities of the target pests. The methodology is applied to a gridded map in which each map cell represents a site in a landscape. The method uses stochastic simulations to depict plausible realizations of the invasion outcomes and estimate the distribution of pest invasion likelihood for each cell in the area of concern. The method then prioritizes the cells based on the stochastic invasion outcomes using a pairwise stochastic dominance rule and a hypervolume indicator. We demonstrate the approach by assessing the relative likelihood of pest invasion for strawberry production in Finland. Our method helps to differentiate sites in a landscape using both the estimates of pest invasion risk and their uncertainty. It can be applied to prioritize sites for plant health surveys and allocate survey resources among large geographic regions. The approach is generalizable and can be used in situations where knowledge of the harmful pest species is poor or nonexistent

Pathways for introduction of invasive pests and the value of production at risk in the different sectors of plant production

Selvityksessä koottiin yhteen eri kasvilajeihin ja tuotannonaloihin liittyvien kasvinterveysriskien arvioinnissa tarvittavaa tietoa a) kasvintuhoojien leviämisväylien volyymistä ja b) eri tuotannonaloilla uhattuna olevan tuotannon arvosta. Selvityksessä katettiin mahdollisimman laajasti kaikki tavara, jonka mukana kasvintuhoojat voivat levitä Suomeen. Lisäksi selvitettiin Suomeen suuntautuvan liikenteen määrät. Suomeen tuotavan tavaran määriä arvioitiin pääasiassa virallisista tilastoista saatujen tietojen avulla. Tuotannon arvoa kuvattiin tuotannon määrän ja tuottajahinnan tulolla. Selvityksessä katettuja tuotteita hankittiin ulkomailta vuosittain yhteensä noin 12 miljardia kg, mistä noin 92 % oli puutavaraa, 7 % elintarvikkeita tai elintarviketeollisuuden raaka-aineita ja 0,2 % lisäysaineistoa. Lisäysaineistoa arvioitiin hankittavan ulkomailta vuosittain noin 2 900 miljardia kappaletta, josta noin 99,7 % oli peltokasvien siemeniä. Selvityksessä arvioitiin yhteensä noin 130 kasvilajin tai -suvun kaupan määrä. Kasvintuotannon arvon arvioitiin olevan yhteensä noin 3,5 miljardia euroa vuodessa. Tästä metsätaloustuotannon arvo oli noin 54 %, peltokasvituotannon noin 31 % ja puutarhatuotannon noin 11 %.Rapporten innehåller information som behövs för att bedöma växtskyddsriskerna för olika växtarter och olika produktionsområden med fokus på a) produktvolymen som utgör spridningsvägar för växtskadegörare och b) värdet på den produktion som hotas inom olika produktionsområden. Rapporten omfattar i så stor utsträckning som möjligt alla produkter som kan sprida växtskadegörare till Finland. Dessutom utreddes volymen på trafiken in till Finland. Mängderna produkter som förs in till Finland uppskattades huvudsakligen med hjälp av officiella statistikuppgifter. Produktionens värde beskrevs utgående från produktionsvolym och producentpriser. Totalt infördes cirka 12 miljarder kg produkter till Finland årligen, varav cirka 92 % var virke och trävaror, 7 % livsmedel eller råvaror för livsmedelsindustrin och 0,2 % förökningsmaterial. Mängden förökningsmaterial från utlandet uppskattades till cirka 2 900 miljarder frön och plantor årligen, av vilka cirka 99,7 % var utsäde för jordbruksgrödor. Antalet växtarter eller -släkten uppskattades till totalt cirka 130 stycken i rapporten. Växtproduktionens värde uppskattades till totalt cirka 3,5 miljarder euro om året. Cirka 54 % av värdet utgjordes av skogsbruksproduktion, cirka 31 % var åkerväxtproduktion och cirka 11 % trädgårdsproduktion.This report compiles basic information needed when assessing the pest risk related to different plant species and sectors of plant production, namely information on a) the volume of pathways of entry and b) the value at risk in the sectors of plant production. The report covers all the products that can act as pathways for pest entry into Finland as comprehensively as possible. Also, the volume of traffic into Finland is reported. The amount of goods traded into Finland was estimated mainly based on official statistics. The value of plant production was assessed based on the volume of production and producer prices. The total amount of the goods traded into Finland was estimated to be about 12 billion kg yearly, of which about 92% were wood and wood products, 7% food and raw materials for the food industry, and about 0.2% propagation material. The total amount of propagation material traded into Finland was about 2 900 billion seeds and/or plants for planting per year. The report covers the trade in about 130 plant species or families. The value of plant production was estimated to be in total about 3.5 billion euros per year. Of this, forestry covers about 54%, field crops about 31% and horticultural production about 11%

Uusien kasvintuhoojien leviäminen pyritään estämään

Kasvintuotanto on nykyisin kansainvälistä toimintaa. Kasvituotteiden mukana voi kulkeutua myös uusia kasvintuhoojia, joiden leviäminen olisi pysäytettävä mahdollisimman aikaisin.vo

Uusien kasvintuhoojien leviäminen halutaan estää

Eviran riskinarviointiyksikössä arvioidaan uusien kasvintuhoojien Suomelle aiheuttamia riskejä. Tavoite on estää uusien, vaarallisten tuhoojien leviäminen Suomeen

Assessing the probability of freedom from pine wood nematode based on 19 years of surveys

Many quarantine pests, such as the pine wood nematode (PWN, Bursaphelenchus xylophilus), are surveyed annually in all EU countries. Although a lot of resources are spent in the surveys, the confidence in pest freedom achieved with them is not commonly analysed. We assessed the probability that Finland is free from PWN, based on the surveys done in 2000–2018. We used the methods employed in the risk-based estimate of system sensitivity tool (RiBESS), which has recently been recommended for quarantine pest applications. We considered two scenarios: 1) the surveys aimed to justify phytosanitary import requirements and to facilitate exports and 2) the surveys aimed to detect invasions early to enable eradication of outbreaks. These differed only in the pest prevalence that the surveys were expected to detect. The surveys appeared to support the assumption that PWN is not present in Finland, but they did not seem extensive enough to ensure early detection of invasions. The sensitivity of the import-export surveys was greater than 0.6 in 13 years, whereas that of the early detection surveys was always below 0.25. The probability of freedom achieved in 2018 following 19 years of surveys increased asymptotically with the mean time between invasions. For the import-export surveys, this probability was at least 0.95 unless the mean time between invasions was less than 13 years. For the early detection surveys, the probability of freedom was less than 0.73 unless the mean time between invasions was 63 years or more. The results were rather robust with respect to the parameters for which exact information was lacking. To improve the assessment, a quantitative estimate of the probability of PWN invasion to Finland and a thorough assessment of the maximum area of an eradicable infestation would be needed. To gain an understanding about the true impact of quarantine pest surveys on biosecurity, more assessments, like the one presented in this paper, are needed

Assessment of the suitability of Finnish climate for the establishment of Fusarium circinatum Nirenberg & O’Donnell

According to the EU plant health law, all Member States must carry out annual surveys for priority pests and emergency measure pests. However, surveys are not required for pests which, due to unsuitable ecoclimatic conditions, cannot become established in the considered Member State. This report presents our assessment of the suitability of the present Finnish climate for the establishment of Fusarium circinatum, the causal agent of pine pitch canker (PPC) and damping-off of pine seedlings, and which is regulated in the EU by emergency control measures. We assessed the suitability of the Finnish climate for the establishment of F. circinatum outdoors by developing a global CLIMEX model for the potential range of PPC. Based on it, we assessed the likelihood of the Finnish climate for being suitable for the occurrence of PPC outdoors to be low, with a low level of uncertainty, and for the establishment of F. circinatum outdoors to be low, with a high level of uncertainty. In addition, based on a literature review, we assessed the likelihood of the temperature and moisture conditions in Finnish forest nurseries being suitable for the establishment of F. circinatum to be high, with a high level of uncertainty.EU:n kasvinterveysasetuksen mukaan kaikkien jäsenmaiden on vuosittain kartoitettava prioriteetti- ja hätätoimenpidetuhoojia. Kartoituksia ei kuitenkaan tarvitse tehdä tuhoojista, jotka eivät ilmastollisten olosuhteiden vuoksi pysty asettumaan kyseiseen jäsenvaltioon. Tämä raportti esittelee arviomme Suomen nykyisen ilmaston sopivuudesta pihkakoroa ja taimipoltetta aiheuttavan Fusarium circinatum -nimisen hätätoimenpidetuhoojan asettumiseen. Arvioimme Suomen ilmaston sopivuutta F. circinatum -tuhoojalle pihkakoron esiintymistä ennustavan CLIMEX-mallin avulla, jonka kehitimme osana arviointityötä. Mallinnustulosten perusteella arvioimme todennäköisyyden, että Suomen ilmasto soveltuu pihkakoron esiintymiseen ja F. circinatum -tuhoojan asettumiseen, olevan pieni. Arvio ilmaston sopivuudesta pihkakoron esiintymiseen Suomessa on melko varma, kun taas arvio ilmaston sopivuudesta tuhoojan asettumiseen Suomeen on epävarma. Lisäksi arvioimme kirjallisuuskatsauksen perusteella todennäköisyyden, että suomalaisten metsätaimitarhojen lämpötila- ja kosteusolosuhteet sopivat F. circinatum -tuhoojan asettumiseen, olevan suuri. Arvio oli kuitenkin hyvin epävarma