We’re smack in the middle of summer vegetable gardening season here in San Diego, and our guess is that if you’ve got one planted, you’re either doing all you can do ward of pests or are starting to see signs of stress in your plants! The presence of pests and pathogens in the garden is entirely natural. Yellow leaves, black spots, holes and wilt are all common symptoms of various plant ailments, but aren’t all necessarily harbingers of doom. It’s important to be able to identify different pests and pathogens, and also to know when they are getting out of control and when to leave well enough alone. Today we’ll look at some of the more common vegetable garden problems and what they mean for your plants.
1.Blossom End Rot
Black, sunken deformities on the bottom of fruits – primarily tomatoes, but also peppers, squash and other fruiting vegetables – are caused by a calcium deficiency. It’s important to know a few things about this disease. First, because it is physiological in nature, it cannot spread between plants. Second, once the deficiency is resolved, the plant will recover and continue to produce normal fruit. Third, it is entirely safe to eat any fruit from a plant with this disease – there is no bacteria or fungus associated with blossom end rot (assuming the plant is otherwise healthy).
It’s important to note that a calcium deficiency does not necessarily mean that there is simply not enough calcium in the soil. More often than not, it has to do more with the fact that the plant is not getting enough consistent water to transport calcium up its stems and to the fruit. During this summer’s drought, keep an eye out for this issue due to infrequent, light or inconsistent watering. Correct and prevent with regular watering and an all-purpose fertilizer from North Park Nursery!
2. Caterpillar or Slug Damage
Probably one of the most common symptoms in garden vegetables. Holes in the leaves can indicate the presence of a number of pests, most commonly caterpillar or slugs. It can be difficult to tell what is munching on your plants, so look for other signs. Slug damage happens mostly at night, while caterpillars can often be seen feeding on the plant during the day. Slugs may leave telltale slime trails while only caterpillars will skeletonize leaves or burrow beneath its surface. In either case, some damage is tolerable and will not kill a plant. However, damage to the leaves of crops like kale, chard or other leafy greens reduces the amount of edible harvest. Treat with a pesticide of your choice: a systemic product like neem oil will provide the best long-term defense, while a contact instecticide – or even manually removing and squashing the offending pests – will be the most immediate solution.
3. Tomato Blight
Tomato blight is a fungal infection of tomatoes that starts as light brown spots progressing to dark, concentric circles, yellowing and, eventually, entire leaf wilt and drop. It is moderately infectious and most easily transferred when watering, as droplets of water will spread the fungus from plant to plant. Prevent blight and growth of other kinds of fungus on any vegetable plant by being sure to water only the soil and not the leaves or stems. Treat infected plants with a spray containing copper. Plants that are too far gone should be removed to avoid spreading the disease.
4. Tobacco Mosaic Virus
Named because it first was discovered in tobacco plants, this is a strain of viruses that can affect tomatoes, squash, cucumbers, peppers and even beans. It’s primary feature is characteristic yellow mottling, or a “mosaic” pattern on the leaves. Symptoms can also include black or brown spotting, and young leaves may become stunted or wrinkled. There is no treatment for plants infected with a mosaic virus. Infected plants should be culled immediately to prevent spread, as most plants will not survive the disease and it is highly contagious.
5. Spider Mites
Fairly easy to identify, the damage of spider mites looks unlike any other pest or pathogen. Leaves of affected plants have an allover white or yellowish stippling that looks like a dusting of powder but cannot be rubbed off. You may or may not be able to see pinhead-sized red mites present on the plant. Treat as you would other pests like caterpillars, mentioned above. Heavily infested plants may exhibit actual webbing similar to a spiders’ and may be best off culled.
There you have it! How to identify some of the most common plant pests and pathogens. In general, follow these rules to ensure a healthy, happy garden:
– Plant a variety of crops and interplant them. Mix tomatoes and leafy greens with rows of squash and peppers. This prevents pests from growing into large, unmanageable colonies and also helps limit the spread of diseases.
– Water only the soil as much as possible, and avoid wetting plant leaves. This will limit the growth of bacteria and fungus, and help prevent the spread of diseases.
– Do not plant too densely. Try to avoid having the canopies or leaves of plants intertwining one another – good airflow is crucial for healthy plants, and physical contact between plants facilitates the spread of pests and disease. You want plants just close enough to shade the soil below in order to prevent the growth of weeds, but not to the point that they become overgrown or entangled.
– If you are concerned about pests, start from the get-go with an organic, natural pest repellant that contains a deterrent like cinnamon, rosemary or clove, or a systemic like neem used as a root drench. These are gentle products that are safe to consume but are most effective used as preventative measures, before a plant becomes sick.
– Head off slugs by using a slug attractant or the age-old beer trick.
Need some organic pesticide, fertilizer or some vegetable starts to get your garden going? Looking for some advice or a more specific plant diagnosis? Give us a call or stop in today!