4.4 Influence of leaf litter on Bti resistance
In the present study, the addition of larval food or leaf litter
particles to Bti toxins for bioassays led to an increase in LC50,
indicating a higher survival rate of larvae in the presence of dietary
particles. Similarly, a decrease in Bt efficacy was found in the
species Choristoneura fumiferana Clem. when larvae were given a
high-quality diet rather than a poor-quality diet.62 Indeed, larvae
may compensate for the lower quality diet by increasing their food
consumption and Bt toxin absorption.62
Furthermore, no variation in resistance level between the LiTOX
and the susceptible strains was observed when larval food or nontoxic
leaf litter was mixed with the commercial Bti toxin mixture.
Many cases of insect–pathogen interactions influenced by plant
compounds have been described.63 For example, previous studies
suggest that plant secondary compounds can affect the expression
of resistance to Btk toxins in phytophagous insects.64 – 66 Results
suggest that in the present case there is no interaction between
the toxicity of Bti toxins and leaf litter particles.