Differences in growth and yield responses to Aphis gossypii Glover between different okra varieties

The reactions of five commercial varieties of okra, Abelmoschus esculentus, to A. gossypii were evaluated under semiarid field conditions. Each experimental plant of varieties Clemson spineless, Clemson spineless 80, Lee, Perkins dwarf, and Local was infested 60 days after emergence by three late-nymphal instars of the aphid. The results showed that aphid populations increased constantly on the varieties, except for days 42 and 49 after infestation, attaining a peak at about the end of the growing season. Differences in aphid densities were recorded between varieties. The aphids were most numerous on var. Local, while lowest in number on var. Lee. Infestation by aphids on okra varieties reduced yield by 57% on var. Perkins dwarf, 56% on var. Lee, 24% on var. Clemson spineless, 21% on var. Clemson spineless 80, and 5% on var. Local. Reduction in the number of pods produced per plant followed the same pattern as observed for total yield. Aphids had not altered significantly the vegetative plant growth at day 37 following infestation. At day 66, a substantial decrease in shoot fresh and dry weights and also leaf area was evident on var. Perkins dwarf while on var. Clemson spineless only the leaf area was significantly reduced. Moreover, aphid-free controls varied widely in their growth and productivity at the end of growing season. Varieties Clemson spineless and Clemson spineless 80 produced the highest total yield and pod numbers, var. Local the lowest. The varieties Perkins dwarf and Clemson spineless produced significantly higher shoot fresh and dry weight, as well as leaf area, than vars. Lee and Local.