Residual activity of insecticides
Residual Activity of Insecticides
Psyllid adults fly into orchards from neighboring areas, and the eggs and nymphs are tucked inside newly forming leaves that are difficult to reach with insecticides. In addition, those new leaves are growing rapidly and often outgrow the insecticides. Thus, the most effective insecticides are those that have translaminar or systemic activity and/or that have a long residual life. Pyrethroids and neonicotinoids, and their combinations, are the longest lasting insecticides. Softer insecticides such as abamectin, and organic insecticides such as Pyganic are very short lived. They must make contact with the insect to kill it and there are virtually no residues. The chart below is evolving as we learn more about the effectiveness of various insecticides in the field. It is meant as a guide, in that insecticides with long residual periods are often the best for situations such as eradicative efforts, very high psyllid densities, bulk citrus, and in HLB quarantine areas. Softer, short residual insecticides may offer adequate control when the psyllid populations are low, but need to be applied frequently.
This chart will be updated as we learn more about the response of psyllids to insecticides in California growing conditions.