Pests and diseases often go hand-in-hand, because many diseases and viruses are spread by insect vectors. (The insects move the diseases from plant to plant as they visit to feed or collect pollen.) The phrase “plant disease” is often used as a catch-all phrase, but diseases can be caused by several different organisms:
- Fungi
- Bacteria
- Viruses
- Nematodes
In addition to various organisms that cause plant disease, a suitable “host organism” has to be present for the disease to grow and spread. If a particular disease only infects tomato roots, but only cucumber roots are present, the disease will eventually die out on its own. This is where the principle of crop rotation comes to play. Disease could still be present in a field or section of garden, but if the right host is not present, the disease will not affect the garden. Brassicas, or plants in the cabbage family, are particularly susceptible to root diseases. These crops must be rotated from year to year within the garden, to avoid losing an entire crop.
Keeping Disease at Bay
In addition to listing common plant diseases, and offering remedies for them, Pleasant also lists tactics to care for the garden to ensure that the garden is as healthy as possible, and able to ward off disease problems on its own. Crop rotation, companion planting, choosing resistant varieties, mulching, paying careful attention to watering, and other gardening techniques can help a garden take care of itself.
Identification when Disease Strikes
Much like the Bug Book, The Gardener’s Guide to Plant Diseases, contains an encyclopedic reference for the most common plant diseases. One long chapter is devoted to plant diseases. For each disease, the following information is included:
- Disease name
- Type of organism that causes it
- Where it occurs
- Making a diagnosis
- Immediate action
- Future management
Some disease listings also include diagrams of the life cycle, spores, or other easily-identifiable aspects of the disease.
Insect or Disease?
A later chapter helps gardeners determine whether the plant problem that they are observing is due to a pest problem or a disease problem. Some insect damage looks like a disease, and vice versa. The table lists the symptom, the plants that are commonly affected, and what to do.
Nutritional deficiencies and soil problems can also masquerade as disease problems. Pleasant offers insight into identifying these deficiencies and methods to correcting them.
Common Crops and their Problems
Every cultivated plant is at risk for pest and disease damage. At the end of The Gardener’s Guide to Plant Diseases is a table including most commonly grown food crops, and their frequent afflictions. The table lists the crop name, the disease problem, symptoms of the disease problem, and tips for growing these plants to keep them healthier.
Together, The Gardener’s Guide to Plant Diseases and The Gardener’s Bug Book are a nearly complete reference for gardeners wishing to identify and respond to pest and disease problems in their garden, while using environmentally friendly measures.