Evaluation of damage to satsuma mandarin (Citrus unshiu) by the leaffooted bug, Leptoglossus zonatus (Hemiptera: Coreidae)

The leaffooted bug, Leptoglossus zonatus (Dallas) (Hemiptera: Coreidae) is a key direct pest of satsuma mandarin (Citrus unshiu Marcovitch) in much of the Gulf Coast region of the United States. The injury and amount of damage to satsuma fruit caused by L. zonatus adults and nymphs at various insect densities (0-3 individuals per fruit) and feeding durations (0-14 days after infestation) were assessed in laboratory and field experiments. The parameters evaluated included fruit damage symptoms, fruit colour, premature fruit abortion (PFA), fruit weight loss (FWL), percentage of damaged sections (PDS), and soluble solids content (SSC) of the fruits. Feeding by L. zonatus on satsuma produced typical damage symptoms including the presence of green spots and dark spots on the outer rind and the collapsing and drying out of the juice vesicles in the inner rind. Insect density and feeding duration had significant effects on most damage parameters. Fruit weight loss and PDS increased with insect density and feeding duration. Soluble solids content decreased with both factors, and was also negatively correlated to PDS. Premature fruit ripening (yellowing) was recorded at densities of 1 or more insects per fruit. Premature fruit abortion was significantly higher in fruits infested by L. zonatus than in uninfested fruits, but insect density may not fully explain the PFA data. Leptoglossus zonatus female and male produced similar amounts of damage, which were slightly more than the damage produced by the nymphs. In general, the results were fairly consistent between laboratory and field experiments, although some minor differences were recorded. The data suggest an economic injury level of 1-2 L. zonatus per satsuma fruit. The results are discussed in relation to the ecology and management of L. zonatus on satsuma.