Biological invasions are currently regarded as a major threat to biodiversity and agriculture all over the world, often resulting in huge economic losses. One of the worst cases in modern history has been the invasion of gypsy moth in the USA. The apparent importance of this issue has brought to life various strategies of invasive species management. However, a comprehensive understanding of the consequences of different strategies is still lacking. In this paper, we consider how the pattern of the gypsy moth spread can be affected by biological control when an infectious disease is introduced in the wake of the spreading species. We first revisit the available information on the gypsy moth's biological traits and argue that the importance of the commonly accepted mechanism of its dispersal by means of “stratified diffusion” may be significantly overestimated. We then consider a diffusion-reaction model of the gypsy moth spread and show that it can produce pattern of spread very similar to what is seen in field observations. Having considered the system’s properties for different strength of the disease, we find that, rather counter-intuitively, the invasion success depends on the magnitude of the controlling effort in a non-monotonous way. An increase in control measures may reinstate the invasion that would fail otherwise. A message to pest control managers is therefore that a better result may sometimes be achieved by investing less money, contrary to what is usually done.

https://github.com/mghaniunair/Mathematica...