Organic Pest Control
From a horticultural standpoint, a pest is a destructive organism that has a detrimental effect on crops or landscape plants. Pests can include insects, pathogens or weeds. Pesticides include herbicides, insecticides, fungicides, and repellents. Learning how to use these in the least toxic way is good for the environment and good for the humans who deal with them.
The first step in controlling pests is to provide the best growing environment for plants. A healthy plant can often ward off an attack from pests without any intervention. Vigilance on the part of the grower to immediately treat small problems will eliminate the need to pull out all the stops for a major attack. Determine a threshold for damage. It is likely that any garden is going to suffer some damage; it is just a matter of deciding how much is acceptable.
The next step in pest control is to correctly identify the pest. What may look like insect damage might actually be a pathogen instead. If there is a question, help is only an email away at: https://hort.extension.wisc.edu/ask-a-gardening-question/.
Once the problem is identified, start with the least toxic method and work up the ladder. Keep in mind that even “organic” pesticides can be hazardous and should be used as a last resort.
Cultural controls are the first and oldest line of defense. Things like crop rotation, soil fertility, plant species selection, pruning, plant spacing, and weed control can all play a part in mitigating both insect and disease control. Choose plants that are labeled disease resistant, promptly remove any diseased plants, and keep tools both clean and in good working order. One of the most common problems is not allowing enough space between plants. This decreases air flow and contributes to fungal diseases. Do not jam a multitude of tomato plants into a small space assuming a higher yield; the highest yield will be blight. Space them appropriately and enjoy a healthier garden.
After cultural controls, the next step is mechanical and physical controls. Fences, barriers, nets, traps, screens, and mulch can all be used to control pests. There is a wide array of fences to keep varmints out of gardens. Traps can include larger traps for mammals as well as sticky traps, light, and pheromone trap for insects. Mulch will help keep weeds and other invasive plants in check. Floating row covers are an underused, but very effective defense against marauding insect pests. The thin material allows for sun and rain penetration while keeping insects out. Timing is a critical factor when using these, especially when used on plants requiring pollination.
Chemical controls are the last option when fighting pests. Some lesser toxic chemicals include insecticidal oils, diatomaceous earth, insecticidal soaps, and neem oil. The oils work by suffocating the pests and is primarily used on the egg and larval stage of insects. Diatomaceous earth is an abrasive material that causes vital fluids to leak from the insect, hence dehydration and death occurs. It is primarily used on ground dwelling insects. The soaps target soft bodied insects and cause cell damage leading to starvation. Neem oil is more systemic, taken up by the plant, so when it is consumed it interrupts the life cycle of the insects. In all cases, these methods are non-specific and effect beneficial insects as well as pests.
Carol Shirk
Certified Master Gardener