The EFSA assessment of Trichilogaster acaciaelongifoliae as biocontrol agent of the invasive alien plant Acacia longifolia: a new area of activity for the EFSA Plant Health Panel?

This paper summarizes the first assessment by the European Food Safety Authority (EFSA) Plant Health (PLH) Panel of a biological control agent (BCA) of an invasive plant. This followed a request by the European Union (EU) Commission to assess the risk to plant health in the EU of an intentional release of the bud‐galling wasp Trichilogaster acaciaelongifoliae for the control of Acacia longifolia. The EFSA PLH Panel also published a statement on the process of assessing the risk of the intentional releases of BCAs of invasive alien plants. Trichilogaster acaciaelongifoliae feeds on A. longifolia and Acacia floribunda. Acacia longifolia is an invasive alien plant species that has a negative effect on biodiversity and ecosystems in Portugal, whereas A. floribunda is not invasive in the EU. Both species are cultivated as ornamental plants in some EU countries. Climatic conditions in the EU are suitable for establishment of T. acaciaelongifoliae where host species are present. This BCA is moderately likely to spread in the EU by natural means, but could be intentionally moved to control A. longifolia in other locations. Its potential effects on invasive A. longifolia and on the cultivated ornamentals were assessed. The EFSA PLH Panel has shown with this work how such advice could be provided in the European Union.     

The regulation of biological control of weeds in Europe – an evolving landscape

After a difficult start, classical biological control of weeds is becoming recognized as an option for management of invasive plants in European Union (EU) Member States with intentional releases in three countries over the past 5 years. Many European countries are benefitting from the presence of Stenopelmus rufinasus, the azolla weevil, which has been accidentally introduced to the region. However, the UK experience with the official release of the psyllid Aphalara itadori against Japanese knotweed (Fallopia japonica) and the subsequent release of the rust Puccinia komarovii var glanduliferae against Impatiens glandulifera showed the regulatory framework that could be followed by EU Member States. This process was followed in advance of the subsequent release of Trichilogaster acaciaelongifoliae, a specific Australian bud‐galling wasp, against the invasive Acacia longifolia in Portugal. Soon the case of Ophraella communa, another accidental introduction that is severely limiting Ambrosia artemisiifolia populations, will influence affected countries, some of which have been uninterested in this technique until now, to consider the advantages and disadvantages of classical biocontrol. The future looks bright for classical weed biocontrol and the EU Regulation on Invasive Species should further aid this situation.     

Phenological dynamics of the invasive plant Acacia longifolia in Portugal

Phenological shifts may play an important role in the success of invasive species. In the coastal regions of continental Portugal, Acacia longifolia is one of the most widespread invasive plants, but there are significant gaps in our understanding and interpretation of its phenology. This study is the first to investigate the phenological variation of A. longifolia and its association with climate in populations representing a temperature and precipitation gradient in mainland Portugal. The results highlighted significant variations in the vegetative (leaf initiation) and reproductive phenophases (bud formation, flowering and fruiting) among populations. Overall, leafing was observed throughout the year, bud formation occurred between summer and spring, anthesis between late winter and the beginning of spring, and fruiting started in late winter. Most of the reproductive phenophases varied across elevation or latitudinal gradients, with populations that were subjected to more stressful climatic conditions advancing their flowering and fruiting phenophases. The occurrence of each phenophase was strongly associated with the climatic conditions in the previous 5–12 months, suggesting that plants receive their phenological cues well in advance of their phenological response. Among climatic factors, temperature and irradiance were the most significant predictors of the phenological cycle of A. longifolia, but precipitation also exerted a greater influence on budding and flowering of the species. The phenological response of A. longifolia in a variety of sites represents an important step towards understanding how its phenology may react to the projected climate change in the Mediterranean region.     

Adapting sampling effort to assess the population establishment of Torymus sinensis,the biocontrol agent of the chestnut gallwasp

Torymus sinensis Kamijo is to date the most effective controlling agent of the chestnut gallwasp Dryocosmus kuriphilus. The procedure to evaluate the parasitism rate of T. sinensis consists of dissecting D. kuriphilus galls collected in the field and checking them for its presence. Such a procedure is, however, time-consuming. Using a space-for-time substitution approach, by creating a temporal gradient within 15 sites and by means of bootstrap simulations, we analysed the effect of different sampling efforts on the precision of evaluating the success of T. sinensis release and the evolution of its parasitism rate towards biocontrol. Results show that after the first release, 200 galls are required to assess its presence with a 1% failure rate. Once T. sinensis is established, 100 galls are generally sufficient to estimate its parasitism rate by accepting a (median) percentage of error of 14% in the second year and 6% and 3% in the third and fourth year, respectively. Finally, we propose a series of design options to reduce the sampling effort according to the targeted accuracy level and as a function of the obtained parasitism rate.     

Survey of indigenous parasitoids affecting the invasive chestnut gall wasp Dryocosmus kuriphilus in the Friuli Venezia Giulia region (North‐East Italy)

The Asian chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae), is one of the most damaging insect pests on Castanea sativa Miller trees (Fagales, Fagaceae) worldwide. Dryocosmus kuriphilus galls were collected between late May and August 2014 from 11 sites in the Friuli Venezia Giulia region of North‐East Italy, differing in elevation and forest cover composition. The number of parasitoids that emerged was higher than the number of D. kuriphilus specimens that emerged for 5 out of 11 sites considered. The mean number of larval chambers per gall dissected was between 1.5 and 2.8 (for the 11 different sites). There were no fewer than 2–3 specimens of parasitoids emerging per 100 galls, in all sites. The parasitoids identified belonged to five different Chalcidoidea families (Torymidae, Eupelmidae, Eurytomidae, Pteromalidae and Eulophidae). Among them, Torymidae and Eupelmidae represented approximately 90% of the total hymenopteran parasitoids. The most represented species were Torymus flavipes (Walker), Megastigmus dorsalis (Fabricius) and Eupelmus urozonus Dalman, all indigenous parasitoids of species causing oak galls. All identified parasitoids were already known to be associated with D. kuriphilus in Italy. These data support the hypothesis of a high species richness of this parasitoid community.     

Effect of plant growth regulators on the shoot gall formation in mango caused by Apsylla cistellata Buckton (Psyllidae: Homoptera) in India

Abstract

Trials were conducted from 1979 to 1983 at Pantnagar on the effect of 2,4‐dichlorophenoxy acetic acid (2,4‐D) (5 to 250 mg/litre), 2,4,5‐trichloroxyphenoxy acetic acid (2,4,5‐T) (5 to 250 mg/litre), 1‐naphthyl acetic acid (NAA) (5 to 500 mg/litre), chlorocholine chloride (CCC) (50,100 mg/litre), naleic hydrazide (MH) (50, 100 mg/litre), abscisic acid (10, 50 mg/litre), gibbrellic acid and Alar (10 and 50 mg/litre) on the gall formation in mango by Apsylla cistellata Guckton. There was no effect on the number of galls formed but abnormal, open, elongated galls were formed in the case of 2,4‐D (100 mg/litre and above) and 2,4,5‐T (150 mg/litre), in which nymphs of A. cistellata could not survive, resulting in control of the pest. No flower panicles emerged on the twigs with no nymphal population.     

Surface contact toxicity and synergism of several insecticides against different stages of the tropical bed bug, Cimex hemipterus (Hemiptera: Cimicidae)

BACKGROUND: Five formulated insecticides (lambda‐cyhalothrin at 10 mg m^?2, bifenthrin at 50 mg m^?2, fipronil at 10 mg m^?2, fenitrothion at 50 mg m^?2, imidacloprid at 5 mg m^?2) and one active ingredient (DDT at 500 mg m^?2) were evaluated using a surface contact method against early and late instars and adults of two strains of the tropical bed bug, Cimex hemipterus (F.). Synergism of lambda‐cyhalothrin and fipronil using piperonyl butoxide (PBO) was also assessed. RESULTS: The order of susceptibility of different stages of bed bugs was as follows: early stage ? lambda‐cyhalothrin > bifenthrin = imidacloprid > fipronil > fenitrothion > DDT; late stage—lambda‐cyhalothrin > bifenthrin > fenitrothion > imidacloprid > fipronil > DDT; adult—lambda‐cyhalothrin > imidacloprid > bifenthrin > fenitrothion > fipronil > DDT. The late instars exhibited significantly higher LT₅₀ among the life stages. The addition of PBO to fipronil increased the susceptibility of the insects. CONCLUSIONS: Lambda‐cyhalothrin, bifenthrin, fenitrothion and fipronil at the recommended application rates were effective against C. hemipterus. Although imidacloprid demonstrated good initial response against C. hemipterus, the insects showed substantial recovery 72 h post‐treatment. The late instars (fourth and fifth instars) should be used as the model for toxicological evaluation. Copyright © 2011 Society of Chemical Industry     

Factors influencing short-term parasitoid establishment and efficacy for the biological control of Halyomorpha halys with the samurai wasp Trissolcus japonicus

BACKGROUND

Classical biological control has been identified as the most promising approach to limit the impact of the invasive pest species Halyomorpha halys (Heteroptera: Pentatomidae). This study investigated the parasitism rate at sites where the biocontrol agent Trissolcus japonicus (Hymenoptera: Scelionidae) was released and where its unintentional introduction took place, in the Trentino–South Tyrol region. The effect of land-use composition was studied to understand which factors favor the establishment of hosts and parasitoids, including native and exotic species.

RESULTS

The released T. japonicus were detected a year after the start of the program, with a significant parasitoid impact and discovery, compared to control sites. Trissolcus japonicus was the most abundant H. halys parasitoid, and Trissolcus mitsukurii and Anastatus bifasciatus were recorded also. The efficacy of T. mitsukurii was lower in sites where T. japonicus was successfully established, suggesting a possible competitive interaction. Parasitism level by T. japonicus at the release sites was 12.5% in 2020 and 16.4% in 2021. The combined effect of predation and parasitization increased H. halys mortality up to 50% at the release sites. Landscape composition analysis showed that both H. halys and T. japonicus were more likely to be found at sites with lower altitude and with permanent crops, whereas other hosts and parasitoids preferred different conditions.

CONCLUSION

Trissolcus japonicus showed a promising impact on H. halys, at release and adventive sites, with minor nontarget effects, mediated by landscape heterogeneity. The prevalence of T. japonicus in landscapes with permanent crops could support IPM in the future. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Studies on insects and mites causing galls on the leaves of common ash Fraxinus excelsior L. in the Ojców National Park in Poland

The occurrence frequency of galls caused by insects and mites on the leaves of Fraxinus excelsior L. was investigated, based on leaf samples collected in the Ojców National Park in 2000–2001. The species composition of galls was identical in two consecutive years. Galls were caused by 5 species a total of 2881 galls. The most numerous species was Dasineura fraxinea (Kieffer) in both years.Index of occurrence frequency and Agrell's index of species co-existence have been calculated. This index reached the highest values in case of Dasineura fraxinea and Vasates fraxini (Nalepa) in 2000 as well as D. fraxinea and Psyllopsis fraxini (L.) in 2001.     

Native and introduced parasitoids in the biocontrol of Dryocosmus kuriphilus in Veneto (Italy)

The invasive gallmaker Dryocosmus kuriphilus is a threat to chestnut stands and it is necessary to control it in order to maintain a satisfactory nut yield. A preliminary evaluation of the native natural enemies emerging from the galls, mainly parasitoids associated with native cynipid gallmakers, revealed that they were not able to contain the pest. Consequently, a classical biological control programme using Torymus sinensis started in 2010, with almost 500 releases being made in 6 years. The parasitoid achieved a satisfactory level of control of the pest over a period of time shorter than expected based on literature related to other countries. The success in the study area might be explained by specific traits intrinsic to T. sinensis, such as its high spread capability via stratified dispersal (i.e. a combination of short‐ and long‐distance flights), together with a large availability of host galls and limited competition with other parasitoids.     

Paradoxical effects of sublethal exposure to the naturally derived insecticide spinosad in the dengue vector mosquito,Aedes aegypti

BACKGROUND: Recent studies have indicated that spinosad, a mixture of two tetracyclic macrolide compounds produced during the fermentation of a soil actinomycete, may be suitable for controlling a number of medically important mosquito species, including the dengue vector, Aedes aegypti L. The authors determined the effects of a 1 h exposure to a 50% lethal concentration (LC₅₀) of spinosad in the larval stage on the wing length, longevity and reproductive capacity of the adult survivors. RESULTS: The LC₅₀ of spinosad for a wild‐caught population of Ae. aegypti from Chiapas, southern Mexico, was estimated to be 0.06 mg AI L^?1 in late third instars. Paradoxically, the female survivors of exposure to this concentration were significantly larger (as determined by wing length) laid more eggs, but were slightly less fertile than control females. This was probably due to elimination of the smaller and more susceptible fraction of mosquito larvae from the experimental population following spinosad treatment. Male survivors, in contrast, were significantly smaller than controls. No significant differences were detected in the adult longevity of treated and control insects of either sex. CONCLUSIONS: The increase in reproductive capacity of spinosad‐treated females did not compensate for mortality in the larval stage and would be unlikely to result in population increase in this mosquito under the conditions that were employed. Sustained‐release formulations would likely assist in minimizing the occurrence of sublethal concentrations of this naturally derived product in mosquito breeding sites. Copyright © 2008 Society of Chemical Industry     

Host-parasite relationships in tobacco plants infected with a root-knot nematode (<Emphasis Type="Italic">Meloidogyne incognita</Emphasis>) population from the Azores

During a nematode survey, severe infections of tobacco feeder roots and heavy soil infestations byMeloidogyne incognita race 1 were found in S. Miguel (Azores islands, Portugal). This is the first record ofM. incognita infection of tobacco in Azores. Morphology of various life stages, analysis of the esterase electrophoretic pattern and differential host tests were used for nematode characterization and identification. Nematode-induced mature galls were spherical and/or ellipsoidal and usually contained more than one female, males and egg masses with eggs. Feeding sites were characterized by the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. Giant cell cytoplasm was aggregated along a thickened cell wall. Vascular tissues within galls appeared disorganized. The relationship between the initial nematode population density and growth of tobacco plants was tested in a glasshouse experiment in which inoculum levels varied from 0 to 512 eggs and juveniles (J₂) cm⁻³ of soil. Seinhorst’s model was fitted to height and top fresh weight data of the inoculated and control plants. Tolerance limits with respect to plant height and fresh top weight of tobacco cv. ‘Erzegovina’ plants toM. incognita race 1 were estimated as 1.25 eggs and J₂ cm⁻³ of soil. The maximum nematode reproduction rate was 404.7 at an initial population density of 4 eggs and J₂ cm⁻³ of soil. http://www.phytoparasitica.org posting March 2, 2004.     

Gallen,gevormd door de schuimcicade,Philaenus spumarius (Fall.)

Summary The galls caused byPhilaenus spumarius have not been often the subject of investigation. The larvae of the so-called frog-hopper were very numerous in the summer of 1957 and caused deformations on many plants. Those may provide much damage to cultivated plants. In a number of plants the larvae cause galls, but they also can live free on the same plant. In this respect the galls differ from other galls which are indispensable for the development of their inhabitants. Such galls, which develop in some cases while they are absent in others are called facultative galls byMolliard.At the end of the article the plants are enumerated which are known to be bearers of galls of the cuckoo-spit insects in the Netherlands.     

Control of Microdochium majus in winter wheat with botanicals – from laboratory to the field

The fungal pathogen Microdochium majus, causing snow mould, seedling blight and foot rot, results in severe yield losses in small grain cereals. There are few options to control this pathogen in organic production. In this study, aqueous extracts or botanical powders prepared from chamomile, meadowsweet, thyme and Chinese galls were tested in vitro against M. majus conidia germination and mycelial growth, respectively. Subsequently, three botanicals were chosen, applied as powders with different seed coating adhesives, and tested for their effect on the incidence of M. majus from naturally infected wheat seed lots and on seedling emergence from soil under controlled environmental conditions. Furthermore, seed treatments with warm water, a bacterial product or one chosen botanical were tested in a growth chamber and in a field experiment over three consecutive years. Of the botanicals tested, Chinese galls showed the highest efficacy in controlling M. majus, reducing conidia germination and mycelial growth by up to 97 and 100%, respectively, and reducing the incidence from infested seeds by up to 59%. In two growth chamber experiments, total seedling emergence increased by up to 30 and 59% compared with the control treatments following an application with Chinese galls. Under field conditions, yield increase through Chinese galls, the bacterial product and the warm water treatment was 19, 10 and 37% compared with the untreated control, respectively. This study demonstrates the potential of Chinese galls to control M. majus in wheat. Options for improved formulations or combinations of heat‐based treatments with Chinese galls are discussed.     

Cystiphora sonchi (Vallot, 1827) (Diptera: Cecidomyiidae), first record for Tunisia and Africa

During 2017 and 2018, from June to October, leaf galls were observed for the first time on Sonchus oleraceus L. (Asteraceae), sow thistle, in Akouda‐Sousse, Tunisia. Leaves with galls were collected and brought to the laboratory. After a few days, adults emerged from the leaf galls. Morphological identification showed the emerged gall midges to be Cystiphora sonchi (Vallot, 1827) (Diptera: Cecidomyiidae). This is the first record of this species in Tunisia and Africa.     

Spatial and temporal dynamics of Meloidogyne minor on creeping bentgrass in golf greens

Meloidogyne minor, first reported on potatoes in the Netherlands in 2004, is an emerging nematode pest in Europe. It damages turfgrass, particularly creeping bentgrass (Agrostis stolonifera) grown on sandy soils such as those of golf greens. However, little is known of the nematode's life history and pathology. In this study, the spatial and temporal distribution of M. minor on a creeping bentgrass green in Ireland was determined over a 15 month period. Cores were taken on transects across yellowing patches of grass caused by nematode damage. Second‐stage juveniles (J2) were absent from the soil from November to February, when soil temperatures were below 10°C. Both galls and egg masses were present throughout the year but were more abundant in late summer and early autumn. More J2, galls and egg masses were present in the top 10 cm of soil than at a depth of 11–20 cm. The nematode population tended to decrease as distance from the centre of the yellow patches increased. The diameter of visual symptoms (yellow patches) was also recorded over the 15 months. The mean diameter of five sampled patches increased from 23·7 cm in June 2003 to 45·2 cm in August 2004. There were 158–193 galls per 100 cm³ soil at the margin of the visible infested area, indicating that this could be the threshold level for visible symptoms.     

Pathogenicity and host‐parasite relationships of the root‐knot nematode Meloidogyne incognita on celery

Pathogenicity and host‐parasite relationships in root‐knot disease of celery (Apium graveolens ) caused by Meloidogyne incognita race 1 were studied under glasshouse conditions. Naturally and artificially infected celery cv. D’elne plants showed severe yellowing and stunting, with heavily deformed and damaged root systems. Nematode‐induced mature galls were spherical and/or ellipsoidal and commonly contained more than one female, males and egg masses with eggs. Feeding sites were characterized by the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. The cytoplasm of giant cells was aggregated along their thickened cell walls and consequently the vascular tissues within galls appeared disrupted and disorganized. The relationship between initial nematode population density (Pi) and growth of celery plants was tested in glasshouse experiments with inoculum levels that varied from 0 to 512 eggs and second‐stage juveniles (J₂) mL^?1 soil. Seinhorst's model y = m + (1 – m)z^P–T was fitted to height and top fresh weight data of the inoculated and control plants. The tolerance limit with respect to plant height and fresh top weight of celery to M. incognita race 1 was estimated as 0·15 eggs and J₂ mL^?1 soil. The minimum relative values (m) for plant height and top fresh weight were 0·37 and 0·35, respectively, at Pi ≥ 16 eggs and J₂ mL^?1 soil. The maximum nematode reproduction rate (Pf/Pi) was 407·6 at an initial population density (Pi) of 4 eggs and J₂ mL^?1 soil.     

Whiteflies on tomato crops in Portugal*

In Portugal during the 1960/1980s, there was intensive development of vegetable crop production, in particular protected crops, of which tomato was the most important. The main producing regions now are Ribatejo e Oeste, Alentejo and Algarve. Tomato presents extensive phytosanitary problems, being host to a wide range of pests, including the whiteflies Trialeurodes vaporariorum, in protected crops, and Bemisia tabaci, in protected and field crops. Portugal has applied for the status of an EU ‘protected zone’ for this latter pest. As B. tabaci is an important vector of a large number of viruses, including tomato yellow leaf curl viruses (TYLCV), a monitoring programme of the tomato crop was implemented in Portugal. Preliminary data are presented concerning B. tabaci in the three main tomato‐growing regions of the country.     

Ophelimus maskelli (Ashmead) et son parasitoïde Closterocerus chamaeleon (Girault) (Hymenoptera: Eulophidae) au Maroc

Leaf galls causing severe damage were observed on Eucalyptus camaldulensis in the Gharb‐Maâmora region in 2002 due to Ophelimus maskelli (Ashmead) (Hymenoptera: Eulophidae) reported for the first time in Morocco. Since then, this pest has spread to other eucalyptus stands nationwide. During field investigations, the authors noted that the degree of infestation of Eucalyptus camaldulensis differs from one region to another and were classified on a three‐level scale: low, moderate or high. The study of the life cycle of the insect in the field and in the laboratory revealed the presence of two generations per year. This work has shown that Closterocerus chamaeleon (Hymenoptera: Eulophidae), a parasitoid used successfully in other EPPO countries as a biological control agent, is present in Morocco. The rate of parasitism was very high, which consequently resulted in the lack of damage caused by the gall pest on Eucalyptus camaldulensis in Morocco.     

In-plant activation of root-specific expression of a cytotoxic gene disrupts the development of the root-knot nematode,Meloidogyne javanica

Plant hosts can be engineered to disrupt the development of sedentary plant-parasitic nematodes or proper functioning of the feeding sites the nematodes induce. The use of constitutive promoters to express dsRNAs or nematode inhibitor proteins may be unreliable because of possible silencing or yield penalty from continuous expression in a plant host. This ill-effect can be avoided if a root-specific, nematode-responsive promoter (NRP) is used to drive the target nematode-inhibitory message. This study used the In Plant Activation (INPACT) system to express a barstar-controlled barnase in galls of Meloidogyne javanica and assessed how the engineered tobacco lines affected the growth and development of the nematodes. Of the 11 combinations of four NRPs and the CaMV 35S promoter assessed, the AtCel1 and TobRB7 combinations activated specific expression of split β-glucuronidase (GUS) and barnase genes in and around giant cells. The same NRP combination directed expression of the barnase gene in tobacco roots also constitutively expressing the barstar gene (SPBB transgenic lines). On roots of six T₁ SPBB lines, there was up to 94% reduction in the number of galls with significantly smaller adult females compared to those on wild-type plants. Some of the females on lines SPBB4-1 and SPBB-4-2, for example, were not associated with galls. The results indicated the engineered plants disrupted M. javanica development and demonstrate the potential for controlled and localized expression of peptides, such as those that could block specific effectors, to disrupt initiation, formation, establishment, or proper functioning of feeding cells induced by damaging sedentary nematodes.