Evaluation and Selection of New Trichogramma spp. as Biological Control Agents of the Guatemalan Potato Moth (Tecia solanivora) in Europe.

The Guatemalan potato moth (Tecia solanivora) is designated a quarantine pest by the European Union, causing severe production losses in potato crops. No effective chemical control alternatives are currently available, and cultural techniques are unable to reduce harvest losses to acceptable levels. With a focus on biological control, two egg parasitoids (Trichogramma euproctidis and Trichogramma achaeae) were selected and evaluated for use under field and storage conditions. Laboratory assays (choice and no-choice) indicated the preference of both parasitoids for T. solanivora vs. Phthorimaea operculella. Trichogramma euproctidis showed the highest parasitic activity for both moths. Analysis of functional response (at 15, 20, 25 and 27 °C) confirmed the high parasitic potential of T. euproctidis. Furthermore, in assays conducted under darkness conditions, T. achaeae was unable to parasitize eggs. However, in semi-field assays, T. achaeae was more efficient in searching for eggs in the soil than T. euproctidis. Based on these results, T. achaeae was selected to be tested under field conditions, and T. euproctidis was selected for testing under storage conditions.

A review of the jumping plant-lice (Hemiptera: Psylloidea) of the Canary Islands, with descriptions of two new genera and sixteen new species.

The psyllid fauna of the Canary Islands is reviewed on the basis of recent field work on Tenerife, La Gomera, La Palma Gran Canaria and Lanzarote, as well as the examination of material deposited in several collections. Two new genera and 16 new species are described: Drepanoza Bastin, Burckhardt & Ouvrard gen. nov., Percyella Bastin, Burckhardt & Ouvrard gen. nov., Agonoscena atlantica Bastin, Burckhardt & Ouvrard sp. nov., A. sinuata Bastin, Burckhardt & Ouvrard sp. nov., Arytaina meridionalis Bastin, Burckhardt & Ouvrard sp. nov., Cacopsylla crenulatae Bastin, Burckhardt & Ouvrard sp. nov., C. falcicauda Bastin, Burckhardt & Ouvrard sp. nov., Diaphorina gonzalezi Bastin, Burckhardt & Ouvrard sp. nov., Drepanoza canariensis Bastin, Burckhardt & Ouvrard sp. nov., D. fruticulosi Bastin, Burckhardt & Ouvrard sp. nov., D. molinai Bastin, Burckhardt & Ouvrard sp. nov., Euphyllura confusa Bastin, Burckhardt & Ouvrard sp. nov., Percyella benahorita Bastin, Burckhardt & Ouvrard sp. nov., P. canari Bastin, Burckhardt & Ouvrard sp. nov., P. gomerita Bastin, Burckhardt & Ouvrard sp. nov., P. guanche Bastin, Burckhardt & Ouvrard sp. nov., Strophingia canariensis Bastin, Burckhardt & Ouvrard sp. nov. and S. paligera Bastin, Burckhardt & Ouvrard sp. nov. Arytaina insularis Loginova, 1976, stat. nov. is elevated from a subspecies of A. devia Loginova, 1976 to species rank. Five new combinations are proposed: Drepanoza fernandesi (Aguiar, 2001) comb. nov., D. lienhardi (Burckhardt, 1981) comb. nov., D. montanetana (Aguiar, 2001) comb. nov., D. pittospori (Aguiar, 2001) comb. nov. and Lauritrioza laurisilvae (Hodkinson, 1990) comb. nov., all transferred from Trioza. The hitherto unknown last-instar immatures are described for Megadicrania tecticeps Loginova, 1976, Cacopsylla atlantica (Loginova, 1976) and Lauritrioza laurisilvae (Hodkinson, 1990). We also report Agonoscena targionii (Lichtenstein, 1874) for the first time from the Canary Islands. Our review increases the number of known psyllid taxa from the Canary Islands to 24 genera and 62 species (one of which remains undescribed). Endemism, host plant relationships and biogeographic patterns are discussed. Keys for the identification of adults and immatures are provided, as well as information on host plants, distribution and predators.

A revision of the Encarsia mexicana species-group (=Dirphys Howard) (Hymenoptera: Aphelinidae), gregarious endoparasitoids of whiteflies (Hemiptera: Aleyrodidae) in the Neotropical Region.

The genus Dirphys Howard 1914 syn. n. is synonymized with Encarsia Förster, and treated as a species-group of Encarsia, referred to henceforth as the Encarsia mexicana species-group. The monophyly of Encarsia is discussed in relation to Dirphys. The new synonymy is based on phylogenetic analyses of the nuclear ribosomal 28S-D2 gene region (43 taxa, 510 bp). The Encarsia mexicana species-group is recovered as strongly monophyletic within Encarsia. All species of the Encarsia mexicana species-group are revised. The group includes six previously described species, and fourteen newly described species. All species are described (or redescribed) and illustrated. Detailed distributional data, and, where available, plant associate and host records are provided for all species. Encarsia myartsevae Kresslein and Polaszek nom. nov. is here proposed as a replacement name for Encarsia mexicana Myartseva, now preoccupied by Encarsia mexicana (Howard). A dichotomous identification key, supplemented by an online multiple-entry key, is provided for all species.

Survey of Candidatus Liberibacter Solanacearum and Its Associated Vectors in Potato Crop in Spain.

'Candidatus Liberibacter solanacearum' (CaLsol), the etiological agent of potato zebra chip (ZC), is transmitted to potato plants by the psyllid Bactericera cockerelli (Sulc, 1909) in North and Central America and New Zealand. The risk of the dispersion of ZC in Spain depends on the presence of an efficient vector. This work studies the presence and abundance of ZC symptoms and CaLsol in potato plants, as well as the presence and abundance of psyllid species associated with potato crops in the main producing areas in Spain. Eighty-eight plots were surveyed punctually to detect ZC symptoms and psyllid species in the main potato-producing areas. Furthermore, fourteen potato plots were surveyed by different sampling methods during the cropping season to detect psyllid species from 2016 to 2018. Very few symptomatic and CaLsol-positive plants were detected in Mainland Spain, and any positive plant was detected in the Canary Islands. Most of the adult psyllids captured were identified as Bactericera nigricornis (Foerster, 1848), and some of them as Bactericera trigonica, but no B. cockerelli was detected. B. nigricornis was found widely distributed in the northern half of the Iberian Peninsula; however, this psyllid does not seem sufficient to pose a threat to potato production, due to the scarce number of specimens and because the frequency of B. nigricornis specimens that were CaLsol+ was very low.

Biological Control Options for the Golden Twin-Spot Moth, Chrysodeixis chalcites (Esper) (Lepidoptera: Noctuidae) in Banana Crops of the Canary Islands.

Chrysodeixis chalcites (Esper) (Lepidoptera: Noctuidae) is a significant pest in banana plantations in the Canary Islands. Field surveys were carried out to identify its naturally occurring parasitoids and estimate their parasitism rates between September 2007 and October 2010. Ch. chalcites was parasitized by six different larval/pupal parasitoid species: Cotesia sp., C. glomerata L. (Hym.: Braconidae), Aplomyia confinis Fallén (Dip.: Tachinidae), Hyposoter rufiventris Perez, Ctenochares bicolorus L. (Hym.: Ichneumonidae) and Aleiodes sp. (Hym.: Braconidae). Among them, Cotesia sp. was the most frequent species, accounting for 8.18% of parasitized larvae. High levels of egg parasitism were detected, with Trichogramma achaeae Nagaraja and Nagarkatti (Hym.: Trichogrammatidae) being the most widely distributed egg parasitoid. A greenhouse assay was also carried out on a commercial banana crop with the aim of evaluating the potential of T. achaeae as a biological control agent and compared with a chemical control. Five periodic inundative releases of 35 adults/m2 every 21 days were necessary to achieve an adequate parasitism level (56.25 ± 1.61%). Moreover, there was 15.75% less foliar damage in the biological control plot compared to the chemical control plot. These results indicate that T. achaeae could be a promising biocontrol agent of Ch. chalcites in greenhouse banana crops.

Feeding and Oviposition Behaviour of Trioza erytreae (Hemiptera: Triozidae) on Different Citrus Rootstock Material Available in Europe.

Trioza erytreae (Del Guercio, 1918) (Hemiptera: Triozidae) is a vector of Candidatus Liberibacter spp., the causal agent of Huanglongbing disease (HLB). This study evaluates the preference of T. erytreae in different citrus seedlings. Thus, six different non-grafted citrus rootstocks were used for these experiments: (a) Carrizo citrange; (b) Citrus macrophylla; (c) 'Cleopatra' mandarin; (d) Forner-Alcaide No. 5; (e) Forner-Alcaide No. 517, and (f) Poncirus trifoliata ('Flying Dragon'). The behaviour and survival of this psyllid was evaluated through the feeding preference of T. erytreae adults for different rootstocks (in a choice trial under greenhouse conditions) and oviposition and survival of T. erytreae adults on the different citrus material (in a no-choice trial under laboratory conditions). Trioza erytreae showed a clear preference for hosting and feeding on C. macrophylla, and Carrizo citrange was the most suitable rootstock for insect reproduction and survival followed by C. macrophylla. Conversely, Poncirus trifoliata was the least attractive rootstock to T. erytreae adults in the greenhouse trial and led to significantly lower T. erytreae survival. Our results suggest that conventional citrus rootstocks, such as Carrizo citrange and C. macrophylla, could increase T. erytreae populations.

Effects of several UV-protective substances on the persistence of the insecticidal activity of the Alphabaculovirus of Chrysodeixis chalcites (ChchNPV-TF1) on banana (Musa acuminata, Musaceae, Colla) under laboratory and open-field conditions.

Alphabaculovirus of Chrysodeixis chalcites (ChchNPV-TF1) has been investigated as a useful bioinsecticide against C. chalcites (Esper) (Lepidoptera: Noctuidae) in banana crops. This study investigated the effects of several substances on the persistence of ChchNPV-TF1 under field conditions in the Canary Islands. Natural photoprotective substances, such as moringa, cacao, green tea, benzopurpurine, charcoal, iron dioxide, benzimidazole, kaolinite, and bentonite, were first evaluated under laboratory conditions using a Crosslinker as UV light source at 200 J/cm2. The photoprotective substances were divided into three groups: low protection (0-8%; kaolinite), intermediate protection (48-62%; green tea, moringa, bentonite and cacao) and high protection (87-100%; charcoal, iron ioxide). Benzopurpurine and benzimidazole did not provide any photoprotective effects. Two of the substances that yielded the best results, 1% cacao and 1% charcoal, were selected for the open-field experiment in a banana plantation. The persistence of ChchNPV-TF1 OBs (occlusion bodies) on leaf surfaces with sunlight exposure was analysed by comparing the initial mortality of 2nd instar C. chalcites larvae with the mortality observed at various intervals postapplication. The mortality rates decreased over time in all treatments and were always higher in the UV-protective substance-treated parcels. The 1% charcoal treatment exhibited the highest protection in both the laboratory and field experiments. No specific interference of UV-protective substances on the maximum photochemical efficiency of banana plants was observed under field conditions.

Sustainable Management Methods of Orchard Insect Pests.

The current need for sustainable resource management is increasingly urgent, as demand for agricultural commodities is rising rapidly as the world's population grows [...].

Effect of Temperature on Life History and Parasitization Behavior of Trichogramma achaeae Nagaraja and Nagarkatti (Hym.: Trichogrammatidae).

Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) is currently used as biological control agent for several lepidopteran pests. Knowledge of thermal requirements is essential to optimize its rearing procedures and inundative releases. The biological characteristics and two-sex life table parameters of T. achaeae were determined at five constant temperatures (15, 20, 25, 30, and 35 °C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. T. achaeae was able to develop and survive from 15 °C to 30 °C, but not at 35 °C. Temperature significantly affected the preadult development time and adult longevity, decreasing when temperature increased from 15 °C to 30 °C. Temperature significantly altered the sex ratio, being female biased between 15 °C and 25 °C. Age-stage, two-sex life table analysis indicated that net reproductive rate (R0) was highest at 20 °C. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased with increasing temperature, while the mean generation time (T) decreased significantly. In addition, functional response of T. achaeae was studied, being significantly affected by temperature and host egg density, displaying a Holling type-I at 15 °C and a Holling type-II at 25 °C. The relevance of these results is discussed for the use of T. achaeae as biological control agent.

'Candidatus Liberibacter Solanacearum' Is Unlikely to Be Transmitted Spontaneously from Infected Carrot Plants to Citrus Plants by Trioza Erytreae.

Bacteria belonging to 'Candidatus Liberibacter spp.' are associated with various severe diseases in the five continents. The African citrus psyllid Trioza erytreae (Hemiptera: Triozidae) is an efficient vector of citrus huanglongbing-HLB disease, absent in the Mediterranean basin. This psyllid is currently present in the islands and mainland Portugal and Spain, where the prevalence of 'Ca. Liberibacter solanacearum' (CaLsol) associated to a carrot disease is high. Trioza erytreae normally feeds on citrus plants but has also been observed on other crops. It would be a great concern to the Mediterranean citrus industry if T. erytreae could transmit this bacterium from carrots to citrus and cause disease; therefore, the transmission of CaLsol from carrot plants to citrus plants was experimentally assessed. Although CaLsol was initially detected on receptor citrus plants in transmission assays by dodder and budding, the infection was not established. The feeding behavior by electrical penetration graphs and oviposition of T. erytreae on carrot plants versus citrus plants was evaluated. Trioza erytreae only reached the phloem in citrus plants. However, it was able to acquire CaLsol from infected carrots but unable to transmit it to citrus plants. CaLsol was detected in some carrot plants immediately after 7 and 14 days (inoculation access period), but it was not detected after one month. Trioza erytreae was unable to complete its life cycle on carrot plants. In conclusion, the efficient vector of bacteria associated to huanglongbing was unable to transmit CaLsol from carrot to citrus plants, but it acquired and transmitted the bacterium from carrot to carrot plants with low efficiency.

Age-Stage, Two-Sex Life Table of Chrysodeixis chalcites (Lepidoptera: Noctuidae) at Constant Temperatures on Semi-Synthetic Diet.

The golden twin-spot moth or tomato looper, Chrysodeixis chalcites (Esper), is a polyphagous and worldwide pest that causes important aesthetic damages to banana fruits in the Canary Islands. The life history parameters of C. chalcites were determined under laboratory conditions in base on the age-stage, two-sex life table at 15, 20, 25, 30, and 35°C, 65% relative humidity (RH), and a photoperiod of 16:8 (L:D) h, when it was reared on a semi-synthetic diet. The results show that C. chalcites was able to develop and survive from 15 to 30°C, but no development occurred at 35°C. Developmental threshold temperatures of the egg, larval, pupal, and total preoviposition stages were 10.42, 11.73, 11.22, and 9.42°C, respectively, and their effective accumulated temperatures were 58.31, 265.96, 118.57, and 562.39 degree-days, respectively. The adult longevity was reduced with increasing temperature, which ranged between 16.27 and 34.85 d for females and between 14.27 and 35.21 d for males. The highest values of net reproductive rate (R0) and fecundity were observed at 25°C, with 232.70 offspring and 1,224.74 eggs, respectively. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased significantly and mean generation time (T) decreased significantly with increasing temperature. These results provide useful information that will allow predicting the impact of climate change on the distribution and population dynamics of C. chalcites and developing successful integrated management programs.

Chrysodeixis chalcites nucleopolyhedrovirus (ChchNPV): Natural occurrence and efficacy as a biological insecticide on young banana plants in greenhouse and open-field conditions on the Canary Islands.

Chrysodeixis chalcites, an important pest of banana crops on the Canary Islands, is usually controlled by chemical insecticides. The present study aimed to evaluate the efficacy of the most prevalent isolate of the Chrysodeixis chalcites nucleopolyhedrovirus (ChchNPV, Baculoviridae) as a biological insecticide. Overall the prevalence of ChchNPV infection in C. chalcites populations was 2.3% (103 infected larvae out of 4,438 sampled), but varied from 0-4.8% on Tenerife and was usually low (0-2%) on the other islands. On Tenerife, infected larvae were present at 11 out of 17 plantations sampled. The prevalence of infection in larvae on bananas grown under greenhouse structures was significantly higher (3%) than in open-field sites (1.4%). The ChchNPV-TF1 isolate was the most abundant and widespread of four genetic variants of the virus. Application of 1.0x109 viral occlusion bodies (OBs)/l of ChchNPV-TF1 significantly reduced C. chalcites foliar damage in young banana plants as did commonly used pesticides, both in greenhouse and open-field sites. The insecticidal efficacy of ChchNPV-TF1 was similar to that of indoxacarb and a Bacillus thuringiensis (Bt)-based insecticide in one year of trials and similar to Bt in the following year of trails in greenhouse and field crops. However, larvae collected at different time intervals following virus treatments and reared in the laboratory experienced 2-7 fold more mortality than insects from conventional insecticide treatments. This suggests that the acquisition of lethal dose occurred over an extended period (up to 7 days) compared to a brief peak in larvae on plants treated with conventional insecticides. These results should prove useful for the registration of a ChchNPV-based insecticide for integrated management of this pest in banana crops on the Canary Islands.

Efficacy of an alphabaculovirus-based biological insecticide for control of Chrysodeixis chalcites (Lepidoptera: Noctuidae) on tomato and banana crops.

BACKGROUND: Chrysodeixis chalcites (Esper) is a major pest of tomato in Mediterranean countries and attacks banana in the Canary Islands (Spain). The efficacy of Chrysodeixis chalcites single nucleopolyhedrovirus (ChchSNPV-TF1) was evaluated in plant growth chambers and greenhouse trials performed on tomato and banana plants respectively. Treatments were applied using a compressed air sprayer. RESULTS: Mean (± SE) lethal infection varied from 77 ± 10% to 94 ± 3% in second-instar larvae fed for 2 days on tomato plants treated with 2 × 10(6) to 5 × 10(7) virus occlusion bodies (OBs) L(-1) , increasing to ∼100% infection after 7 days. Mortality of larvae collected from banana at different intervals post-application varied from 54 ± 10% to 96 ± 4% in treatments involving 1 × 10(8) -1 × 10(9) OBs L(-1) , whereas indoxacarb (Steward 30% WG) and Bacillus thuringiensis var. kurstaki (Biobit 16% WP) treatments produced between 22 ± 6% and 32 ± 5% pest mortality. All treatments significantly reduced plant defoliation compared with untreated controls. Application of 1 × 10(9) OBs L(-1) was 3-4-fold more effective than chemical or B. thuringiensis treatments. Larvae acquired lethal infection more rapidly when feeding on tomato than banana plants, but this difference disappeared following >60 min of feeding. CONCLUSION: This information should prove useful in the registration of ChchSNPV-TF1 as a bioinsecticide in the Canary Islands and Europe.

Biological control strategies for the South American tomato moth (Lepidoptera: Gelechiidae) in greenhouse tomatoes.

The South American tomato pinworm, Tuta absoluta (Meyrick) has been introduced into new geographic areas, including the Mediterranean region, where it has become a serious threat to tomato production. Three greenhouse trials conducted in tomato crops during 2009 and 2010 explored control strategies using the egg-parasitoid Trichogramma achaeae Nagaraja and Nagarkatti compared with chemical control. The effectiveness of the predator Nesidiocoris tenuis (Reuter) was also tested. In greenhouses with early pest infestations (discrete generations), periodic inundative releases (eight releases at a rate of 50 adults/m2, twice a week) were necessary to achieve an adequate parasitism level (85.63 +/- 5.70%) early in the growing season. However, only one inoculative release (100 adults/m2) was sufficient to achieve a comparatively high parasitism level (91.03 +/- 12.58%) under conditions of high pest incidence and overlapping generations. Some intraguild competition was observed between T. achaeae and the predator, N. tenuis. This mirid species is commonly used in Mediterranean greenhouse tomato crops for the control of the sweetpotato whitefly, Bemisia tabaci (Gennadius). Tomato cultivars were also observed to influence the activity of natural enemies, mainly N. tenuis (whose average numbers ranged between 0.17 +/- 0.03 and 0.41 +/- 0.05 nymphs per leaf depending on the cultivar). This may be because of differences in plant nutrients in different cultivars, which may affect the feeding of omnivorous insects. In contrast, cultivar effects on T. achaeae were less apparent or possibly nonexistent. Nevertheless, there was an indirect effect in as much as T. achaeae was favored in cultivars not liked by N. tenuis.

Analysis of abamectin residues in avocados by high-performance liquid chromatography with fluorescence detection.

In this work an analytical method for the determination of abamectin residues in avocados is developed using high-performance liquid chromatography (HPLC) with fluorescence (FL) detection. A pre-column derivatization with trifluoroacetic anhydride (TFAA) and N-methylimidazole (NMIM) was carried out. The mobile phase consisted of water, methanol and acetonitrile (5:47.5:47.5 v/v/v) and was pumped at a rate of 1 mL/min (isocratic elution). The fluorescence detector was set at an excitation wavelength of 365 nm and an emission wavelength of 470 nm. Homogenized avocado samples were extracted twice with acetonitrile:water 8:2 (v/v) and cleaned using C(18) solid-phase extraction (SPE) cartridges. Recovery values were in the range 87-98% with RSD values lower than 13%. The limits of detection (LODs) and quantification (LOQs) of the whole method were 0.001 and 0.003 mg/kg, respectively. These values are lower than the maximum residue limit (MRL) established by the European Union (EU) and the Spanish legislation in avocado samples.