Forecasting the timing and abundance of pest infestations in Citrus at the regional level with temperature data

Abstract: The level of abundance reached by populations of many phytophagous arthropods in an area varies from year to year depending on the temperatures recorded in the area in previous periods. This allows to predict in advance the behavior of pests and improve pest management systems based on data from monitoring networks established in the area. With data on the level of annual mean infestation in the entire citrus area of the eastern Spain citrus belt for several citrus pests between 2004 and 2016 we have related the moment of increase and the maximum abundance reached by these pests throughout the year with previous temperatures in the area. The data come from monitoring networks with which the population level has been continuously estimated in numerous plots distributed throughout the eastern Spain citrus area over those 13 years. The correlation of daily temperatures (mean, maximum and minimum) at different periods of time with moment of increase and maximum annual infestation has been analyzed for four pests, the aphid Aphis spiraecola Patch, the citrus leaf miner Phyllocnistis citrella (Stainton), the California red scale Aonidiella aurantii (Maskell) and the citrus mealybug Planococcus citri (Risso). We found a significant correlation between temperature in previous periods and abundance of the pests, which has a predictive value. The correlation is higher with the timing of the population increase than with the annual maximum of the population. The best correlated period occurs generally 1 to 5 months prior to the timing of the increase and from 0 to 3 months prior to the annual maximum. In years with higher temperatures, the timing of population increase always happens before, but the annual maximum may be higher (as in Aonidiella aurantii and the citrus mealybug) or lower (as in aphids and the leafminer).