Álvaro Rodríguez-González

Inhibitory activity of Beauveria bassiana and Trichoderma spp. on the insect pests Xylotrechus arvicola (Coleoptera: Cerambycidae) and Acanthoscelides obtectus (Coleoptera: Chrisomelidae: Bruchinae)

Xylotrechus arvicola is an important pest in vineyards (Vitis vinifera) in the main Iberian wine-producing regions, and Acanthoscelides obtectus causes severe post-harvest losses in the common bean (Phaseolus vulgaris). Under laboratory conditions with a spray tower, the susceptibility of the immature stages of X. arvicola and A. obtectus against the entomopathogenic fungi Beauveria bassiana and four strains of Trichoderma spp. was evaluated. Both insect pests T. harzianum and B. bassiana showed a good inhibitory activity, accumulating an inhibition on the eggs of values above 85 and 82%, respectively. T. atroviride and T. citrinoviride had a lower inhibitory activity, with inhibition values of 74.1 and 73.3% respectively. These fungi can be considered a highly effective tool for the control during the immature stages of these species.

Development of a qPCR Strategy to Select Bean Genes Involved in Plant Defense Response and Regulated by the Trichoderma velutinum - Rhizoctonia solani Interaction.

Bean production is affected by a wide diversity of fungal pathogens, among them Rhizoctonia solani is one of the most important. A strategy to control bean infectious diseases, mainly those caused by fungi, is based on the use of biocontrol agents (BCAs) that can reduce the negative effects of plant pathogens and also can promote positive responses in the plant. Trichoderma is a fungal genus that is able to induce the expression of genes involved in plant defense response and also to promote plant growth, root development and nutrient uptake. In this article, a strategy that combines in silico analysis and real time PCR to detect additional bean defense-related genes, regulated by the presence of Trichoderma velutinum and/or R. solani has been applied. Based in this strategy, from the 48 bean genes initially analyzed, 14 were selected, and only WRKY33, CH5b and hGS showed an up-regulatory response in the presence of T. velutinum. The other genes were or not affected (OSM34) or down-regulated by the presence of this fungus. R. solani infection resulted in a down-regulation of most of the genes analyzed, except PR1, OSM34 and CNGC2 that were not affected, and the presence of both, T. velutinum and R. solani, up-regulates hGS and down-regulates all the other genes analyzed, except CH5b which was not significantly affected. As conclusion, the strategy described in the present work has been shown to be effective to detect genes involved in plant defense, which respond to the presence of a BCA or to a pathogen and also to the presence of both. The selected genes show significant homology with previously described plant defense genes and they are expressed in bean leaves of plants treated with T. velutinum and/or infected with R. solani.

Field evaluation of 3-hydroxy-2-hexanone and ethanol as attractants for the cerambycid beetle pest of vineyards, Xylotrechus arvicola

BACKGROUND The beetle Xylotrechus arvicola (Coleoptera: Cerambycidae) is a serious pest of vineyards in the Iberian Peninsula. In previous work, the male beetles, but not females, were shown to produce (R)-3-hydroxy-2-hexanone, and female beetles were attracted to this compound in a laboratory bioassay. In this study, release rates of 3-hydroxy-2-hexanone from different dispensers were measured in the laboratory, and the attractiveness of these to X. arvicola adults was determined in trapping tests in three traditional wine-growing regions in Spain. RESULTS As a result of laboratory experiments, for field experiments 3-hydroxy-2-hexanone was formulated as 100 μL in a polyethylene sachet (50 mm × 50 mm × 250 µm), and ethanol was formulated as 1 mL in a polyethylene press-seal bag (76 mm × 57 mm ×50 µm). Field catches were similar at all three study sites. Catches in traps baited with 3-hydroxy-2-hexanone alone were not significantly different from those in unbaited control traps, but catches in traps baited with 3-hydroxy-2-hexanone and ethanol in separate sachets, with 3-hydroxy-2-hexanone and ethanol in the same sachet or with ethanol alone were significantly greater than those in control traps. These results confirm that the beetles are attracted to ethanol, and the addition of 3-hydroxy-2-hexanone does not seem to make any difference. CONCLUSIONS Attraction of females for the male-produced compound (R)-3-hydroxy-2-hexanone has been observed in laboratory but not in field experiments. Traps baited with ethanol are highly attractive to both sexes of adults of X. arvicola, and these can be used for improved monitoring of the adult emergence and for population control by mass trapping.

Control of egg and neonate larvae of Xylotrechus arvicola (Coleoptera: Cerambycidae), a new vineyard pest, under laboratory conditions

Background and Aims Xylotrechus arvicola (Coleoptera: Cerambycidae) is a new vineyard pest. Six insecticides were tested on X. arvicola eggs arranged in Petri dishes and in two parts of the vine: branch and trunk. Method and Results According to the Abbott formula, on Petri dishes, chlorpyrifos had total ovicidal control, significantly different from that of pyriproxyfen (88.3%), Beauveria bassiana (84.3%) and imidacloprid (80.9%). On branches, chlorpyrifos (91.6%), pyriproxyfen (79.1%) and flufenoxuron (75.0%) showed improved toxic effect, and on trunks, chlorpyrifos (83.3%) gave the best control, significantly different from that of imidacloprid (50.0%), pyriproxyfen (45.8%) and flufenoxuron (37.5%). Larval mortality was registered from the seventh to the fourteenth day after treatment: spinosad (50.0%), imidacloprid (45.8%) and B. bassiana (33.3%) were the insecticides that showed greater larval mortality on branches. These insecticides also showed greater larval mortality on trunks, but only B. bassiana (50.0%) had a greater residual effect on trunks than on branches. Conclusions All insecticides evaluated gave better ovicidal control when applied directly on Petri dishes than when applied on branches and trunks, where all insecticides (except chlorpyrifos and imidacloprid) show greater toxic effect when applied on branches. Spinosad and B. bassiana have the best larval residual mortality, when applied, respectively, on branches and on trunks. Significance of the Study Beauveria bassiana is the best insecticide with residual effect on neonate larvae on trunks, where the greater thickness of the rhytidome and cracks favoured the development of this fungus to invade actively the larvae through their shell and proliferate inside.

Investigations of Trichoderma spp. and Beauveria bassiana as biological control agent for Xylotrechus arvicola, a major insect pest in Spanish vineyards

Xylotrechus arvicola (Olivier) (Coleoptera: Cerambycidae) is an important pest in vineyards (Vitis vinifera) in the main wine-producing regions of Spain. Effective control of this pest is difficult due to the biology of this pest. Biological control agents (BCAs) have proven to be an effective tool in controlling and preventing the spread of a variety of plant pests and diseases. Consequently, the aim of the present study was to assess the capacity of different Trichodema spp., isolated from various vineyards and one commercial isolate of Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae), as BCAs of X. arvicola. Isolates of Trichoderma spp. and one isolate of B. bassiana were evaluated against X. arvicola eggs, larvae and adults. Trichoderma harzianum and Trichoderma gamsii demonstrated a good ovicidal control, 100.0% with T. harzianum and over 92.0% with T. gamsii. These Trichoderma strains achieved an over 65.0% larval mortality and 87.5% adult mortality. B. bassiana was the most effective treatment against X. arvicola larvae. These results confirm that Trichoderma spp. can be used to inhibit egg development. In addition, Trichoderma spp. and B. bassiana can help to prevent larvae boring into vines and to kill adults. Therefore, Trichoderma spp., especially T. harzianum and T. gamsii, and B. bassiana can be considered as highly effective BCAs of X. arvicola in vineyards.

Effects of adults body size and larvae diet on the fecundity and percent fertility of eggs laid by Xylotrechus arvicola (Coleoptera: Cerambycidae) females, insect pest in Spanish vineyards

Xylotrechus arvicola is a pest of grape in some vine‐producing regions of the Iberian Peninsula. Biological parameters and relationships (fecundity and percent fertility of eggs in relationship to body size) of females obtained in the laboratory and captured in vineyards were studied. In laboratory conditions, the mean developmental time of larvae ranged from 384 to 392 days and pupal stage varied between 12 to 14 days. Body size (BS) of X. arvicola females was significantly bigger than males. Fecundity was greater in the laboratory (147 eggs) than in the field (50 eggs) females, but the percent fertility of the laboratory eggs was lower (16 eggs). Laboratory females showed a bigger relationship between the production of eggs and BS than females captured in vineyards. Wild females (PDO Ribera del Duero and Tierra de León) had a positive relationship between the percent fertility of eggs and the BS. No correlation between the percent fertility of eggs and the BS was displayed by females captured in PDO Toro, but these females had a higher percent fertility (53 eggs) than the others PDOs. These biological parameters and relationships studied suggest that the artificial diet may lack certain essential nutrients that vine varieties can provide that favor the fertility of eggs. This explains why wild females have the potential to become a problem pest in the Tempranillo grape variety, with bilateral cordon and bush vines training systems that have the highest incidence of this cerambycid.

Evaluation of commercial and prototype traps for Xylotrechus arvicola (Coleoptera: Cerambycidae), an insect pest in Spanish vineyards: Trap types for Xylotrechus arvicola control

Background and Aims: An important factor for the success of a mass capture strategy to control cerambycids involves the selection of an effective trap–lure combination. Therefore, the aim was the evaluation of traps with lures and their efficacy for monitoring and mass trapping of Xylotrechus arvicola. Methods and Results: Three trap types, Crosstrap, Delta and Screen-adhesive, with lures baited with ethanol, were evaluated during 4 years in vineyards of two cultivars. The Crosstrap obtained the greatest catches during 2013 in Tempranillo (29.6 adults/trap) and Prieto Picudo (12.9 adults/trap). All trap types showed similar periods of greatest catches in both cultivars. Conclusions: The Crosstrap achieved the greatest number of adults captured in both cultivars. The Delta and Screenadhesive had few catches. The Tempranillo has proved to be more susceptible to attack by this insect than Prieto Picudo. The capture period varies from 30 to 50 days in the same cultivar in different years. Low temperature during spring delays the appearance of adults. Significance of the Study: The Crosstrap baited with ethanol captured the greatest number of X. arvicola adults. This trap can be used to improve monitoring of adult emergence and for controlling this pest by mass trapping.

Response to rearing in laboratory of the xylophagous grape pest, Xylotrechus arvicola (Coleoptera: Cerambycidae)

Xylotrechus arvicola (Olivier) (Coleoptera: Cerambycidae) is an important pest in vineyards (Vitis vinifera) in the main Iberian wine‐producing regions. Larvae were reared with Semi‐Synthetic Iglesias (SSI) diet over 27 months and two generations in the laboratory. Larval mortality was highest during the first (49.49 %) and second (9.38 %) month of rearing, increasing to 50.52 % during the first month if F2 reared larvae were obtained from an F1 adult female obtained in laboratory. The diet had sufficient nutrients to enable the pest to complete its life cycle within nine months, with F1 larval viability ranging from 23.49 % to 27.97 % and F2 larval viability reduced to 2.07 %. However, the diet did not allow for the completion of additional life cycles and generations (F3, F4,…). Larval mortality increased as the months of rearing (66.13 %, 69.51 % and 89.50 %) and generations (59.10 % and 76.93 % in F1 and F2, respectively) progressed in the laboratory. The larva–adult period of females obtained in the laboratory was longer than for males. In the laboratory, the life cycle was shortened in relation to the life cycle in the field because larvae did not require a cold period to break diapause and start pupation. This indicates that X. arvicola has the potential to complete its life cycle inside grape wood in vineyards of wine‐producing regions with warmer winters.