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Aphid Control With Benefits
Alternative aphid spray timings may help prune growers reduce pesticide runoff.
WIN-WIN outcomes, where both sides of a conflict benefit and there are no outright winners or losers, allow both sides to address an issue and move on to other problems/challenges. Agriculture and the environment have had several win-win developments in the past decade, including pheromones for pest monitoring and/or control, micro-irrigation, and effective, soft pesticides. Until recently, when dormant applied pesticides were found in some California rivers, dormant insecticide sprays were generally viewed as a win-win situation for growers and the environment. University of California (UC) researchers now appear to have found a win-win adjustment to the traditional dormant spray for prune growers and the environment.
A dormant organophosphate insecticide spray like diazinon (Diazol, Makhteshim-Agan of North America), chlorpyrifos (Lorsban, Dow AgroSciences), methidathion (Supracide, Syngenta Crop Protection), etc. plus oil was once the foundation of a good integrated pest management (IPM) program in California stone fruit and almond orchards. It suppresses or controls peach twig borer (PTB), San Jose scale (SJS), red mites, and aphids (in prune orchards), without harming beneficial insects and mites or leaving a pesticide residue on fruit. Many prune growers can apply a dormant spray and forget about targeted pests for that season.
However, organophosphate insecticide levels high enough to kill small fish and tiny crustaceans have been measured in some rivers in California's Central Valley - the heart of California orchard country. Spikes in surface water pesticide levels have been measured, primarily, following major rainstorms in January and February, and put the state of California in violation of federal clean water laws. Although urban use of these pesticides have contributed to the problem, California stone fruit and nut growers are coming under increasing pressure to voluntarily reduce or eliminate pesticide runoff or face the loss of effective and relatively inexpensive pesticides (i.e., diazinon) and, more importantly, possible blanket restrictions on spraying practices.
All of this has put California prune growers in a bind. Generally, aphids are prune growers' biggest pest problem. Only broad spectrum synthetic pesticides give long term aphid control and are registered in prunes. Spray oil (6 to 8 gallons per acre) effectively suppresses mealy plum aphids in-season, but won't control aphid eggs in the dormant season or aphids in curled leaves. Use of broad spectrum materials for aphid control after petal fall can harm beneficial insects and mites, "flaring" spider mites, and possibly requiring use of expensive miticides to avoid defoliation.
Currently, in-season aphid control in prunes can leave growers with a bigger pesticide bill compared with dormant control, and pesticide residue(s) on the fruit - an issue in some important markets. So, if a traditional dormant spray is good for growers and consumers, but potentially bad for the environment, is there a win-win fix?
Next - Finding An Alternative - page 2 of 3
AMERICAN/WESTERN FRUIT GROWER - February 2005
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