Smart insecticide use is up to you

Questions frequently arise regarding insecticide applications on fruits and vegetables. While I cannot offer clear and specific recommendations on all situations you may encounter, here are a few thoughts to help you navigate your insect issues.

First, should you spray? We all want easy solutions to our problems. Insects feed on plants, pesticides kill insects, therefore we should spray for insects…accurate rational but often off target. A certain level of insect damage should be expected and acceptable to you. In farming scenarios economic thresholds can help us make decisions on what level of damage is acceptable. In your home landscape, that choice is more personal than economic driven. We should recognize that with all actions come consequences. Spraying to treat aphids or spider mites may also kill beneficial predators, leading to a speedy rebound in the pest population. In addition, spraying any flowering plant with insecticide may kill pollinators. I am not saying don’t spray, just follow the label and make informed decisions.

Second, consider the least forceful options first. Insecticidal soaps and horticultural oils work mostly through direct contact and have much less impact on beneficial insects. The use of these does take more attention to spray coverage and effort to target the insects (underside of leaves for example). These are even more effective against spider mites than ‘traditional’ insecticides which require a miticide. Neem oil is another unobtrusive option. It comes from a tree extract with natural insecticidal properties. It is also important to note that some pests we observe at one time of the year may be better targeted at a particular time. Leaf mites often seen on apples and pears, and scale insects fall into this category.

Third, overuse of a single insecticide or insecticide family can lead to resistant populations. Selection for resistance can occur if a small proportion of the insect population is able to survive treatment with insecticide. These resistant individuals reproduce and pass on their resistance to offspring. If an insecticide with the same mode of action is repeatedly used against this population, an even greater proportion will survive. Ultimately, the once-effective product no longer controls the now resistant population. Utilizing pyrethroid (permethrin, bifenthrin etc), carbamate (carbaryl), neonicotinoids (imidacloprid) as well as oils and soaps prevent resistance development.

Lastly, knowing pesticide properties and insect cycles can greatly improve your insecticide efficacy. You might use the right insecticide but apply it before insects are present. For example, spraying malathion now to control codling moth (wormy apples) won’t help because it only lasts for 5-7 days and will be gone before codling moth adults start to lay their eggs. Conversely you might not use an insecticide when you could because you are nervous about applying it to a fruit or vegetable you soon plan to eat. While pesticide labels can be confusing and hard to read, the information is there to help you know how to safely use that product. On the new version of Sevin (active ingredient Zeta-cypermethrin) and with permethrin, many vegetables can be used within a day or two of treatment. Other insecticides have much longer intervals prior to harvest. Verify that the pest and the plant are on the label. It will tell you what has been tested to be safe.

Insecticides are valuable tools, but only in the hands of those knowledgeable enough to use them effectively.