Occupancy of the territory by Lymantria dispar (L.) (Lepidoptera Erebidae) egg masses as a predictive index of damage

In Sardinia (Italy) the population abundance of the defoliator gypsy moth Lymantria dispar (L.) (Lepidoptera Erebidae) has been regularly sampled for over thirty years by counts of egg masses. This monitoring activity allows annual identification of the areas with the highest abundance of infestation in order to define the areas to be subjected to phytosanitary treatments and thus to confine the damage caused by gypsy moth defoliation. However, the identification of areas to be treated have been defined exclusively according to the experience gained over the years by the operators. To overcome the limitation of this empirical approach we have developed an objective method supporting decision making based on the relationship between the percentage of infested sites and the intensity of defoliation. For this purpose the radius of annual gypsy moth expansion was estimated in a cork oak district: the estimated value was ca. 6 km per year. This value was used to calculate the percentage of sites occupied by at least 1 egg mass within that radius. A generalized linear model was used to evaluate the statistical significance of the relationship between percentage of occupied sites and presence of damage. According to what we know from literature a monitoring site was considered damaged when defoliation level of foliage was greater than 50%. We then used the historical series of data to calculate the probability that a defoliation event would occur according to the estimated model. The logit model confirmed the validity of the predictor with respect to the presence of damage, with a general accuracy greater than 90%. The results suggest a revision of the sampling protocol used thus far, which requires a particularly costly and prolonged sampling effort. The method described herein should allow easier identification of forest areas exposed to damage and timelier planning of control interventions

The effects of fecundity, mortality and distribution of the initial condition in phenological models

Pest phenological models describe the cumulative flux of the individuals into each stage of the life cycle of a stage-structured population. Phenological models are widely used tools in pest control decision making. Despite the fact that these models do not provide information on population abundance, they share some advantages with respect to the more sophisticated and complex demographic models. The main advantage is that they do not require data collection to define the initial conditions of model simulation, reducing the effort for field sampling and the high uncertainty affecting sample estimates. Phenological models are often built considering the developmental rate function only. To the aim of adding more realism to phenological models, in this paper we explore the consequences of improving these models taking into consideration three additional elements: the age distribution of individuals which exit from the overwintering phase, the age- and temperature-dependent profile of the fecundity rate function and the consideration of a temperature-dependent mortality rate function. Numerical simulations are performed to investigate the effect of these elements with respect to phenological models considering development rate functions only. To further test the implications of different models formulation, we compare results obtained from different phenological models to the case study of the codling moth (Cydia pomonella) a primary pest of the apple orchard. The results obtained from model comparison are discussed in view of their potential application in pest control decision support

Comments on the concept of ultra-low, cryptic tropical fruit fly populations

Desde sus primeras pinturas como la ‘Plaza de Italia’ en 1913, Giorgio De Chirico ha sido uno de los pintores más influyentes del pasado siglo. La Casa Malaparte construida en 1937 y diseñada por el arquitecto Adalberto Libera ha sido una de las aclamadas obras del Movimiento Moderno pero con un reconocimiento tardío. No hay ninguna documentación de que la Casa Malaparte haya estado influenciada por la pintura Chiriquiana pero ambas obras están estrechamente relacionadas. La manera de entender y representar el espacio, la cercana relación entre paisaje y arquitectura, la utilización de un mismo lenguaje, el tratamiento del suelo, la importancia del horizonte, el juego de color y de luces, el dinamismo de su composiciones dentro de una profunda atemporalidad o la descontextualización son puntos tangentes en ambas obras. Propiedades y recursos que construyen unas atmósferas únicas. A partir de una comparación teórica y gráfica se investigan estos aspectos en común. Se llevan a cabo transformaciones en el lenguaje visual, basadas en métodos surrealistas, sobre las pinturas y la documentación de la casa. Esta serie de transformaciones modifican el propio proyecto y se revelan de una manera diferente. Asimismo los dos ambientes se comparan con el fin de ver si la casa podría haber estado influenciada por su pintura

Population models for threshold-based control of Tetranychus urticae in small-scale Kenyan tomato fields and for evaluating weather and host plant species effects

The spatial distribution of motile life stages of the two-spotted spider mite Tetranychus urticae Koch in Kenyan small-scale tomato fields was described by Taylor's power law and an enumerative sampling plan was designed for research purposes. The exponential increase of T. urticae populations during three growing seasons permits the development and use of a simple exponential model for the design of a threshold-based chemical control system. For this purpose, a critical threshold of 440 motile mites per sample unit at the end of the growing season (12 weeks after transplanting) was translated into a proportion of 0.83 infested units in sample 3, i.e. five weeks after transplanting. A sequential binomial sampling plan with respect to the proportion of 0.83, five weeks after transplanting, was designed. The exponential model was extended to account for the influence of weather and host plant species. Model development and parameter estimation were based on three data sets (Kenyan tomato fields, Italian and Californian strawberry fields). The model satisfactorily predicted a positive influence on growth rates by (i) changing the host plant from tomato to strawberry, and (ii) temperature, while a negative effect resulted from (iii) rainfall; both (ii) and (iii) are controlled by temperature-rainfall interactions. In contrast, the estimated parameter values did not satisfactorily describe the expected responses at specific temperature and rainfall values. Nevertheless, the model allowed the rating of host plant species in the field. A fourth data set from Swiss apple orchards was used to test the model, and population build-up on the apple host plant appeared to be higher than on tomatoes but lower than on strawberry. © Springer Science+Business Media B.V. 2006

Modelling the potential distribution of Bemisia tabaci in Europe in light of the climate change scenario

BACKGROUND:Bemisia tabaci is a serious pest of agriculturalandhorticultural crops ingreenhousesandfields aroundtheworld. This paper deals with the distribution of the pest under field conditions. In Europe, the insect is currently found in coastal regions of Mediterranean countries where it is subject to quarantine regulations. To assess the risk presented by B. tabaci to Europe, the area of potential establishment of this insect, in light of the climate change scenario,was assessed by a temperature-dependent physiologically based demographicmodel (PBDM). RESULTS: The simulated potential distribution under current climate conditions has been successfully validated with the available field records of B. tabaci in Europe. Considering climate change scenarios of+1and+2 ∘C, range expansion by B. tabaci is predicted, particularly in Spain, France, Italy, Greece and along the Adriatic coast of the Balkans. Nonetheless, even under the scenario of +2 ∘C, northern European countries are not likely to be at risk of B. tabaci establishment because of climatic limitations. CONCLUSION: Model validation with field observations and evaluation of uncertainties associated with model parameter variability support the reliability of model results. The PBDM developed here can be applied to other organisms and offers significant advantages for assessing the potential distribution of invasive species

Climate warming effects on grape and grapevine moth (Lobesia botrana) in the Palearctic region

The grapevine moth Lobesia botrana (Den. & Schiff.) (Lepidoptera: Tortricidae) is the principal native pest of grape in the Palearctic region. In the present study, we assessed prospectively the relative abundance of the moth in Europe and the Mediterranean Basin using linked physiologically-based demographic models for grape and L. botrana. The model includes the effects of temperature, day-length and fruit stage on moth development rates, survival and fecundity. Daily weather data for 1980-2010 were used to simulate the dynamics of grapevine and L. botrana in 4506 lattice cells across the region. Average grape yield and pupae per vine were used as metrics of favourability. The results were mapped using the grass Geographic Information System (http://grass.osgeo.org). The model predicts a wide distribution for L. botrana with highest populations in warmer regions in a wide band along latitude 40°N. The effects of climate warming on grapevine and L. botrana were explored using regional climate model projections based on the A1B scenario of an average +1.8°C warming during the period 2040-2050 compared with the base period (1960-1970). Under climate change, grape yields increase northwards and with a higher elevation but decrease in hotter areas. Similarly, L. botrana levels increase in northern areas but decrease in the hot areas where summer temperatures approach its upper thermal limit. © 2017 The Royal Entomological Society

Assessing the risk of establishment and transient populations of Spodoptera frugiperda in Europe

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is an invasive pest threatening crop production and food security worldwide. High concerns are linked to the potential establishment of the species in Europe. The high migratory capacity of S. frugiperda causes concerns about the potential impacts of transient populations invading new areas from suitable hotspots. In the present work, we developed and used a physiologically-based demographic model to quantitatively assess the risks of S. frugiperda in Europe. The risks were assessed considering a best-, a median-, and a worst-case scenario. The Mediterranean coastal areas of Southern Europe resulted particularly suitable for the establishment of the species, with suitable areas reaching even higher latitudes, in the worst-case scenario. In Europe, up to four generations per year were predicted. The predicted yearly average number of moths per trap per week (± standard deviation) was 5 (± 4), 17 (± 5), and 139 (± 22) in the best, median-, and worst-case assessment scenarios, respectively. Model results showed that Southern and Central Europe up to the 48th parallel north might be exposed to the risk of transient populations. Depending on the latitude and on the period of arrival of the propagule, 1–2 transient generations per year might be expected. The model can be used to define strategies for reducing the risks of establishment of the pest at the country level. Predictions on the dynamics and phenology of the pest can also be used to support its management at the local level