The sugar-cane borer (SCB), Diatraea saccharalis (F.), and the ratoon stunting disease (RSD) bacterium independently caused significant reductions in stalk weight, cane tonnage and sugar yield. A three-fold difference was found in the comparison of per cent loss of cane tonnage due to RSD alone with that due to the disease in combination with SCB damage in first ratoon sugar-cane. Variance analysis failed to detect interaction between damage by SCB and that by RSD. The data analysed were obtained from an experiment of six replication which evaluated the effects of SCB damage and RSD on sugar-cane yield in Louisiana. We used the randomized complete-block experimental design with split-plot arrangement of treatments. Three schedules of insecticide application to the growing cane, against SCB were the main plots whilst the subplots comprised of RSD inoculation vs. no inoculation of sugar-cane plants grown from seed canes with light vs. severe SCB damage.

Gravid Lucilia treated topically with ivermectin (0.05μg/g, which represented approx. 4% of the 48 hr LD50) laid fewer viable egg batches (less than 50% of controls) and more sterile ones, when compared to untreated (P = 0.019) and acetone-treated flies (P = 0.028). This effect was also seen when mature third instar larvae were dosed with 7.6 μ g ivermectin/g (P = 0.0075 and 0.016 respectively); number of viable egg batches produced were only 25% of the number laid by the progeny of untreated larvae.

Dosage with fenthion stimulated an increase in the number of viable egg batches laid when incorporated in the original larval feeding medium at 0.2 μg/g liver; fewer viable egg batches were laid by the flies which developed from mature larvae treated with 7.6 μ g fenthion/g. Acetone solvent alone had a mild stimulatory effect on topically dosed flies.