Preferences and demographic parameters of cowpea aphid on advanced lines of semiprostrate cowpea
Abstract: The objective of this work was to determine the preference and the demographic parameters of cowpea aphid (Aphis craccivora) in advanced lines of semiprostrate cowpea (Vigna unguiculata), and to verify both the existance and type of plant resistance to this insect attack. Aphid preference to 20 cowpea genotypes was tested in a randomized complete block design, with six replicates. Lines showing the highest levels of resistance and susceptibility in the preference tests were selected for use in the demographic parameter tests. Based on aphid birth rate and mortality, fertility life tables were constructed. The MNCO4-792F-123 line was classified as resistant. The lowest values for cowpea aphid intrinsic and finite growth rates were obtained for the MNCO4-792F-123, and the highest ones for MNCO4-782F-108 and 'BRS Novaera' genotypes, whose levels exceeded those of 'Vita 7', the standard genotype for susceptibility. The MNCO4-792F-123 line is the least favorable for the development of cowpea aphid, while MNCO4-782F-108 and 'BRS Novaera' are the most susceptible ones.