2.4 Pests monitoring and forecasting
Insect prediction models
Insects are unable to regulate their temperature internally, and therefore their development depends on the temperature to which they are exposed. Studies of insect population dynamics often involve modelling growth as a function of ambient temperature.
The most common model for development rate, often called degree-day summation, assumes a linear relationship between development rate and temperature between lower and upper development thresholds. This method works well for optimal temperatures. Temperature-dependent development in insects can also be considered over developmental time. Degree-day models have long been used as part of decision support systems to help farmers predict when to spray or when to control pests.
Ecological life tables are one of the most useful tools in the study of population dynamics of insects with discrete generations. Such tables record a series of sequential measurements that reveal population changes during the life cycle of a species in its natural environment. Long-term data from carefully designed population studies, in which all relevant factors have been accurately measured, are important for constructing population models that are appropriate to biological reality. The goal of life history analysis is to develop a population model that mimics reality. In addition to generating population estimates, this analysis is best done by carefully identifying and measuring the independent factors that cause mortality, such as parasitoids, predators, pathogens, and weather factors. From life table studies, the key factor responsible for increases and decreases in numbers from generation to generation can be identified.