Compatibility of Insecticides with Natural Enemies to Control Pests of Greenhouses and Conservatories

Natural enemies used as biological control agents may not always provide adequate control of plant-feeding insects in greenhouses and conservatories. Research continues to assess the utilization of natural enemies in conjunction with biorational insecticides including insect growth regulators, insecticidal soaps, horticultural oils, feeding inhibitors, and microbial agents (entomogenous bacteria and fungi, and related microorganisms); and the potential compatibility of both strategies when implemented together. A variety of factors influence the ability of using natural enemies with insecticides. These include whether the natural enemy is a parasitoid or predator, the species of the natural enemy, life stage sensitivity, rate and timing of insecticide application, and mode of action of the insecticide. Insecticides may impact natural enemies by affecting longevity (survival), host acceptance, sex ratio, reproduction (fecundity), foraging behavior, emergence, and development. Despite the emphasis on evaluating the compatibility of natural enemies with insecticides, it is important to assess if this is a viable and acceptable pest management strategy in greenhouses and conservatories.

Effects of pH, Aluminum, and Calcium on Survival and Growth of Eggs and Fry of Brook Trout (Salvelinus fontinalis)

Freshly fertilized eggs, eyed eggs, yolk-sac fry, and swim-up fry of brook trout (Salvelinus fontinalis) were exposed to a matrix of 84 combinations of pH (4.0–6.5), aluminum (0–1000 μg/L), and calcium (0.5–8.0 mg/L) in 21–91-d experiments. The response to pH, aluminum, and calcium exposure was dependent on life stage. Sensitivity to acid toxicity generally decreased with age (freshly fertilized eggs>eyed eggs>yolk-sac fry = swim-up fry). Survival or hatching of freshly fertilized and eyed eggs decreased at pH 5.2 and below, whereas survival of yolk-sac and swim-up fry was reduced at pH 4.4–4.0. Sensitivity to aluminum toxicity generally increased with age (freshly fertilized eggs = eyed eggs<yolk-sac fry<swim-up fry). At low pH, survival of freshly fertilized and eyed eggs increased with exposure to increasing aluminum concentrations, in contrast, elevated aluminum [Formula: see text] was often toxic to fry. Increasing calcium was beneficial to all life stages, although the magnitude of this benefit depended on life stage and on the specific pH and aluminum concentration. Survival after previous exposure to toxic combinations of pH, aluminum, and calcium generally improved during a post-exposure recovery period at pH 6.5. However, increased mortality in many exposure combinations did not begin until this recovery period.