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The species regulates its developmental period, fecundity and intrinsic rate of increase in response to developmental changes of the mustard plant and maintains its dispersal throughout the duration of the mustard crop. In succeeding generations on a mustard plant new born nymphs take increasingly longer time to develop into adults and over the same period these adults produced decreasingly fewer numbers of offspring. One adult can give birth to 25-133 nymphs. From generation of a nymph, an aphid takes 7-10 days to produce a nymph. In a calendar year, up to 45 generations of aphids have been recorded. The insect-pest is prevalent throughout the year, but its peak activity is observed during Dec-Mar. In the inflorescence and fruiting stages of mustard plants a higher proportion of the nymphs developed into alates.
Favourable weather condition
Maximum temperature in the preceding week ranging 20–29oC, more so at a narrower maximum temperature range of 22–25oC as also by a morning relative humidity (RH) of >92%, favoured further when >98% and daily mean RH of >75%, cloudy weather favoured aphid build-up. Empirically, long hours of leaf wetness and minimum temperature >5oC during the preceding 3 days also favoured the aphid infestation.
Survival
The pest survives on other Brassica host plant for some time after the rapeseed mustard crop is harvested. The winged form migrates to the hilly part of the country and passes the unfavourable season there on Brassica crops as wingless form. As soon as the favourable conditions prevail in plains, the wings reappear and aphid migrates to the plains of the country.
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