Insects and Diseases in the Garden: Scouting 101

As the summer progresses pests are likely to become a part of your garden. You might have already seen those faint spots that foretell the powdery mildew that will soon be visible on most of your zucchini plants. I know I have. Managing garden insects and diseases is essential for a long bountiful harvest. Even the most prolific variety of tomato or zucchini can have low yields if their resources are spent fighting leaf spots and rots. Commercial growers have a wide range of chemical and cultural controls that they can employ to manage diseases. Home gardeners, on the other hand, have limited chemical options; and most prefer to abstain from chemical controls entirely. This limits us to cultural options, insecticidal soaps, and some sprays, combined into an integrated pest management or IPM approach. IPM uses a combination of multiple techniques to manage pests below a certain threshold. This means that you’ll still probably get disease and insects, but the emphasis will be on keeping it at low levels.

While the slug is no where to be seen, the damage is clear. Low levels can be tolerated, but too much damage and yield becomes reduced.

 While much can be done with plant spacing, attracting beneficials, and rotating crops, at this point in the season we can't change those things. So, we are in defense mode. The first step in defense-mode management is going to be scouting. If you can catch the disease or insect early on, you have a better chance of minimizing its effects. Scouting involves walking through your garden plot and looking for symptoms or signs of disease and insects. Symptoms could be wilting or yellowing leaves, a dark leaf spot, or maybe a discolored fruit. Just to be clear, not every spot you see is going to be a disease, not every insect is damaging, and not every time a leaf wilts is it going to mean you have a root rot. But if there has been plenty of rain and a plant is still wilting, that is a good indicator that you might have a disease. 

These chlorotic (yellowing) leaves could be a symptom of insects, disease or nutrient deficiency.

 Scouting should be done every week. Typically garden plots are small enough that you should be able to find the time to walk through them weekly. It could even be while you are pulling weeds or harvesting. When you scout try to look at both the tops and undersides of the leaves (many insects hide underneath the canopy), and if you see something suspicious make note of it. Diseases can progress very quickly when weather conditions are suitable, and some insects like aphids can have explosive growth in their populations. I went to one commercial grower’s field that was covered in rotting fruit, and he swore that he had been out scouting last week and everything looked healthy. Later that same week though, the weather conditions became perfect for the disease (and the pathogen was present in his field) and the entire field was lost. 

Just a week ago a single leaf from this plant was wilted. Now the whole vine is collapsing.

If properly and consistently done, scouting can help us to identify and start managing small problems before they become huge problems.