Trap crops were evaluated for harlequin bug control in broccoli field plots
in 1994 and 1995. Mustard and rape prevented low densities of harlequin bug
from reaching broccoli, but at high densities the insect moved from the trap
plants into the broccoli. This indicates that harlequin bugs that are attracted to
trap plants may damage the protected broccoli if their numbers are not
prevented from increasing.
Harlequin bugs were shown to have two and a partial third generation a
year. Trissolcus murgantiae Ashmead and Ooencyrtus johnsoni Howard, were
identified as egg parasitoids. Their combined parasitization levels for the two
years were 8% and 37%. T. murgantiae accounted for 87% and 96% of the
parasitization, respectively..
When 19.6 cm and 11.9 cm broccoli plants were exposed to five densities
of harlequin bug adults a negative correlation between plant mortality and insect
density was observed (y = 38.00 - 2.32x, r2 = 0.95 and y = 22.17 - 1.17x, r2 =
0.99, respectively). No correlation was observed in broccoli plants 11.9 tall..
Host plants affected harlequin bug development. Nymphs developed
faster when reared on rape in comparison with mustard. The preoviposition time
for rape reared nymphs was shorter than mustard reared insects. Fecundity and
viability of eggs were not different for harlequin bugs reared at different sex
ratios.
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