Influence of Bacillus thuringiensis application timing on population dynamics of gypsy moth in Mediterranean cork oak forests.

BACKGROUND: The gypsy moth, Lymantria dispar, is one of the main pests of oak forests worldwide and causes extensive defoliation during its periodic outbreaks. In the Mediterranean region, control of gypsy moth populations in cork oak forests is based on application of Bacillus thuringiensis serovar kurstaki (Btk) formulations. This research investigated the effects of Btk applications carried out in two different population development phases on gypsy moth population dynamics. With this aim, temporal and spatial fluctuation patterns of L. dispar egg density were monitored in cork oak forests treated with Btk applications from 2004 to 2009 in Sardinia (Italy). RESULTS: Applications undertaken during the progradation and culmination phases protected the oak canopies equally in the year of application, leading to a similar decrease in pest population density in the following year. However, the medium-term effectiveness of Btk differed between the two application timings, because only applications in the culmination phase caused a gradual decrease in L. dispar infestations throughout subsequent years. By contrast, when the application was undertaken during the progradation phase, population density increased again after 2-3 years. Moreover, Btk applications in the culmination phase reduced significantly the number of years in which gypsy moth density was damaging compared with those done in progradation. CONCLUSIONS: Our results indicate that Btk applications during the culmination phase were more effective than those in the progradation period, because application in the latter case did not suppress the population, but only postponed the outbreak peak by 2-3 years. © 2019 Society of Chemical Industry.

Tacking the vector of Xylella fastidiosa: geo-statistical analysis of long-term field observations on host plants influencing the distribution of Phylaenus spumarius nymphs.

The meadow froghopper, Philaenus spumarius L., is endemic in Italy and was not considered a harmful species until 2014, when the olive quick decline syndrome (OQDS) showed up in Apulia (southern Italy). It was immediately suspected and then verified as the main vector of Xylella fastidiosa, the bacterium responsible for the disease. Currently, EU Directives consider the fight against P. spumarius compulsory in member states and recommend Integrated Pest Management (IPM), both in uncultivated and cultivated infested areas, to minimise the environmental impact of chemical pesticides. This should be based on an improved knowledge of the vector with its seasonal trends and feeding habits linked to specific herbaceous species. In this context, our field study was aimed to improve the understanding of the vector nutritional behaviour, especially at its critical nymph stage, by monitoring its presence on different herbaceous target species, using its typical feeding foams as key indicator. The study area was in Lazio region (central Italy), dedicated to olive growing and still unaffected by the X. fastidiosa plague. Over two years, during the nymph development period, field data have been acquired over the test area and then analysed by coupling statistical (ANOVA), geographical information system (GIS) and geo-referenced field sampling approaches. Results highlighted that P. spumarius exhibits significant preferences for specific herbaceous plants, especially at its early development stages, detectable by tenuous spittle. This indicates female oviposition activity, which seems also not influenced by olive tree proximity. Furthermore, the non-host plant species identified here could be suitable for creating green barriers for limiting the vector diffusion to contiguous areas where sensible plantations are growing. In the final section, applied implications arising from the present findings for P. spumarius population management are discussed.

Influence of mating disruption on the reproductive biology of the vine mealybug, Planococcus ficus (Hemiptera: Pseudococcidae), under field conditions.

BACKGROUND: Although mating disruption is increasingly being used to control the worldwide grapevine pest vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), its mode of action remains unclear. A 3-year field experiment was carried out to investigate the effects of mating disruption on the development and reproduction of the vine mealybug. The influence of mating disruption applied over consecutive years on the pest population density was also evaluated. RESULTS: The percentage of ovipositing females was significantly reduced in disrupted plots by 18.8-66.2%, depending on the year. The absence of ovipositing females in disrupted plots in the autumn of the second and third years indicates the effectiveness of mating disruption throughout the whole growing season. Mating disruption consistently prolonged the pre-oviposition period in all years by up to 12.5 days. CONCLUSION: Our findings provide new insights into the mechanisms underlying the pheromone-based control of the vine mealybug and indicate that the reduction of the pest population density is attributable to both a decrease and a delay in female mating. In addition, the population density of vine mealybugs under mating disruption decreased over the years, indicating that consecutive applications of this control strategy would significantly increase the effectiveness of control of the vine mealybug by mating disruption. © 2018 Society of Chemical Industry.

Spatial distribution and sequential sampling plans for Tuta absoluta (Lepidoptera: Gelechiidae) in greenhouse tomato crops.

BACKGROUND: The within- and between-plant distribution of the tomato leafminer, Tuta absoluta (Meyrick), was investigated in order to define action thresholds based on leaf infestation and to propose enumerative and binomial sequential sampling plans for pest management applications in protected crops. RESULTS: The pest spatial distribution was aggregated between plants, and median leaves were the most suitable sample to evaluate the pest density. Action thresholds of 36 and 48%, 43 and 56% and 60 and 73% infested leaves, corresponding to economic thresholds of 1 and 3% damaged fruits, were defined for tomato cultivars with big, medium and small fruits respectively. Green's method was a more suitable enumerative sampling plan as it required a lower sampling effort. Binomial sampling plans needed lower average sample sizes than enumerative plans to make a treatment decision, with probabilities of error of <0.10. CONCLUSIONS: The enumerative sampling plan required 87 or 343 leaves to estimate the population density in extensive or intensive ecological studies respectively. Binomial plans would be more practical and efficient for control purposes, needing average sample sizes of 17, 20 and 14 leaves to take a pest management decision in order to avoid fruit damage higher than 1% in cultivars with big, medium and small fruits respectively.

Mating disruption of Planococcus ficus (Hemiptera: Pseudococcidae) in vineyards using reservoir pheromone dispensers.

Mating disruption field experiments to control the vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), were carried out in 2008 and 2009 in two commercial vineyards in Sardinia (Italy). The effectiveness of mating disruption was evaluated by testing reservoir dispensers loaded with 100 mg (62.5 g/ha) and 150 mg (93.8 g/ha) of the sex pheromone in 2008 and 2009, respectively. The number of males captured in pheromone traps, the P. ficus population density and age structure, the parasitism rate, the percentage of ovipositing females, and the crop damage were compared between disrupted and untreated plots. In both field trials, the number of males captured in mating disruption plots was significantly reduced by 86% and 95%, respectively. Mating disruption at the initial dose of 62.5 g/ha of active ingredient gave inconclusive results, whereas the dose of 93.8 g/ha significantly lowered the mealybug density and modified the age structure, which showed a lower percentage of ovipositing females and a higher proportion of preovipositing females. Mating disruption did not affect negatively the parasitism rate, which was higher in the disrupted than in the control plots (>1.5-fold). Crop damage at harvest was very low in both field trials and did not differ between treatments. Mating disruption was effective in wide plots protected with dispensers loaded with 150 mg of the sex pheromone, showing its potential to be included in the overall integrated control programs in Mediterranean wine-growing regions.