The introduction of the ragweed leaf beetle in the South of Russia in 1978–1989 was
accompanied by a number of spectacular phenomena that determined the general success of
the ragweed control and further dispersal and acclimatization of the beetles:
(i) formation of solitary population waves (SPW), characterized by an
extremely high density of the phytophage population at the narrow band of the front of a
moving wave defoliating nearly all ragweed plants, and (ii) rapid, within
5-6 generations, development of flight in the leaf beetle species that in its homeland
lost the ability to fly. We present here a demogenetic model capable of reproducing both
these phenomena, assuming that the flight ability of a phytophage population is governed
by a single diallelic locus with flight and flightless alleles that determine three
genotypes of the ragweed leaf beetle. Simulation results agree well with the practical
recommendation of retaining a high density of common ragweed in the release area in order
to provide the necessary conditions for the initial increase of the leaf beetle population
and the formation of the wave. The model confirms the earlier hypothesis that the SPW is
the key factor that determines efficiency of weed biocontrol program. We demonstrate also
that the formation of the wave has crucially accelerated the development of the beetles’
ability to fly.