Diversity, Pests, and Diseases
In spite of all the blessings that diversity brings to your edible landscape,
it also has its hazards. Some plants - called host plants - harbor pests and
diseases. While a host plant may not succumb to its own infestations, it can
infect other, more vulnerable edible plants. Table 3.1 lists a number of suspect
wild and cultivated plants. If you know that a pest or disease on the list
is a problem in your area, avoid using the host plants. Your neighbors may
grow them, but you have a measure of protection from your relative isolation.
If you must grow an ornamental that is listed as a host plant, watch for the
first signs of its pests or diseases on other plants (and when you see them,
don't automatically reach for a poison spray.)
Growing these plants in your edible landscape does not guarantee that your
food plants will be infected or attacked. As an example, consider the last
listing - German chamomile. One summer at the Farallones Institute Rural Center
a bed of chamomile grew only 20 feet from a bed of strawberries. Commercial
growers of strawberries do not allow chamomile to grow that close because
it harbors the lygus bug, which causes a dimple or puckering in the berry
(called cat-facing); and while the fruit and plant are not harmed, the cat-facing
is considered cosmetically unacceptable. At Farallones, very few of the fruits
had cat-faces.
You need only to consider reducing the diversity of plants in your landscape
if your area has a high incidence of the pests and diseases mentioned. For
example, I always rake up or mulch over dead leaves, since apple scab is a
problem in my area. And I always try to limit the number of wild umbellifers
near my vegetables, to reduce the chances of infestations of carrot maggots.
However, I don't bother to eradicate chickweed and mallow near the vegetables,
because my landscape is never troubled with cucumber mosaic virus. To reiterate...a
diverse community of plants must be carefully planned and must exclude problem
plants for your area.
Insects That Spread Diseases
Some insects can be agents for disease-such insects are called vectors. Some
pests, such as aphids on peppers, may not cause a direct problem. The green
peach aphid, however, is a vector of the potato virus, which can harm the
pepper plant and reduce its yields. Table 3.2 lists a number of vectors for
diseases of edible plants.
Don't reflexively reach for insecticides (even "organic" sprays)
at the sight of the first insect. Pull out the plants that look infected,
see if a problem develops, and spray only as a last resort.
|
| Host Plant |
Disease/Pest |
Endangered Edible |
|
| Perrenial Wild Plants |
Aster yellows |
Carrot, lettuce |
| Lilac, cherry, pear, poplar, rose, forsythia |
Bacterial blights |
Beans, lima beans |
| Catnip, chickweed, jimsonweed, mallow, nightshade,
pokeweed, wild lettuce, checkweed seed |
Cucumber mosaic virus |
Cucurbits, celery, lettuce |
| Wild umbellifers (carrot, celery, etc.) |
Celery mosaic virus |
Celery |
| Seed of wild brassicas |
Downly mildew |
Brassicas |
| Perennial wild plants |
Watermelon mosaic virus |
Cucurbits |
| Clovers, vetches, alfalfa |
Viruses |
Peas |
| Wild solanums |
Tobacco etch virus |
Peppers |
| Alfalfa |
Alfalfa mosaic virus |
Peppers |
| Southern grasses |
Leaf spot |
Corn |
| Johnson grass |
Maize dwarf mosaic |
Corn |
| Johnson grass |
Maize chlorotic mosaic |
Corn |
| Wild grasses, oats, wheat, barley, rye, stinkgrass,
foxtail, panicum |
Wheat streak mosaic |
Corn |
| Wild and ornamental plants |
Spotted wilt |
Tomatos |
| Dead leaves on ground |
Scab |
Apples, pears |
| Pyracantha |
Fire blight |
Apples, pears |
| Cedar trees, hawthorn |
Cedar apple rust |
Apples |
| Dandelion, clover |
Blossom-end rot |
Apples, pears |
| Plantain |
Aphids |
Apples |
| White oak, oak tree roots |
Armillaria, clitocybe, and white root rots |
Many fruit and nut trees |
| Dead leaves on ground |
Cherry leaf spot |
Cherries |
| Lamb's-quarters, pigweed, nightshade, ground cherry |
Verticillum wilt |
Stone fruits, vegetables |
| Peppers, eggplants, horse nettle, chokecherry |
X-disease |
Peaches, cherries |
| Wild umbellifers (carrot, cow parsnip, fool's parsley) |
Carrot maggot |
Carrots |
| German chamomile |
Lygus bugs |
Strawberries |
|
|
| Vector |
Disease |
Endangered Edible |
|
| Insects |
Angular leaf spot |
Beans |
| Insects |
Choanephora wet rot |
Cucurbits |
| Insects |
Cercospora leaf spot |
Beets |
| Leafhoppers |
Aster yellows |
Carrots, lettuce |
| Green peach aphids, aphids, cucumber beetles |
Cucumber mosaic virus |
Cucurbits, lettuce, tomatos, celery |
| Green peach aphids, aphids |
Celery mosaic virus |
Celery |
| Green peach aphids, aphids |
Watermelon mosaic virus |
Cucurbits, legumes |
| Cucumber beetles |
Squash mosaic virus |
Cucurbits |
| Cucumber beetles |
Bacterial wilt |
Cucurbits |
| Aphids |
Viruses |
Peas |
| Green peach aphid, potato aphid |
Tobacco etch virus |
Peppers |
| Green peach aphid, aphids |
Potato virus |
Peppers |
| Green peach aphid |
Alfalfa mosaic virus |
Peppers |
| Aphids |
Blight |
Spinach |
| Flea beetles |
Stewart's bacterial wilt |
Corn |
| Insects |
Smut |
Corn |
| Aphids |
Maize dwarf mosaic |
Corn |
| Leafhoppers |
Maize chlorotic mosaic |
Corn |
| Toxin from wheat curl mite |
Kernel red streak |
Corn |
| Leafhoppers |
X-disease |
Peaches, cherries |
| Nematodes (in soil) |
Stem pitting |
Stone fruits |
| Leafhoppers (bluegreen sharpshooter) |
Pierce's disease |
Grapes |
|
Reprinted with permission from:
Designing and Maintaining Your Edible Landscape Naturally, by Robert
Kourik. Metamorphic Press, 1986. To order write to Box 1841, Santa Rosa CA,
95402. OR call (707) 814-2606. $50 + $5 shipping.
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