A series of experiments was conducted to determine
the effect of imidacloprid on the number of Metarhizium
anisopliae and Beauveria bassiana conidia found
on the cuticle of first instar Diaprepes abbreviatus
following different treatments. Larvae treated with
M. anisopliae conidia and imidacloprid by dipping
removed significantly fewer conidia from their cuticle
when in contact with soil or a food source compared
with fungal-treated larvae alone. In addition, more
M. anisopliae and B. bassiana conidia were found on
the cuticle of larvae treated with imidacloprid while
exposed to soil at 7 and 14% moisture resulting in
higher larval mortality and mycosis. Conidial attachment
to cuticles of untreated larvae was higher atF1%
compared with 7 and 14% soil moistures. M. anisopliae
conidia were distributed uniformly over the pleural
membrane of the larval cuticle of both untreated and
imidacloprid-treated larvae. However, fewer conidia
were attached to specific sites such as setae and setal
sockets of treated larvae. At 12 h after treatment,
imidacloprid-treated larvae had fewer conidia removed
from exposed cuticle, setae, and spiracles than
did untreated larvae. Cuticular exposure to imidacloprid
at doses G0.01% (AI) affected conidial attachment
of M. anisopliae negatively. Conidial number decreased
sevenfold at 0.1% (AI). Comparative data on
the effect of imidacloprid formulation on conidial
attachment showed that components of the inert ingredient
were responsible for lower conidial attachment
on larval cuticle at higher insecticidal doses.