UC Master Gardener Program of Alameda County
University of California
UC Master Gardener Program of Alameda County

Reduce Pests and Diseases By Changing Your Cultural Practices


Often, the best way to deal with pests and diseases in a vegetable garden is by avoiding them altogether. You can do this by changing the timing of your planting of a specific crop so that you avoid a pest altogether or you can select a disease resistant variety of a susceptible vegetable crop. You can also use things like barriers, traps or protective covers to exclude a pest from your crop.

Timing Your Crop to Avoid Insect Pests

The first thing you need to do to use this method is to identify what is eating your plant. This might be obvious as with aphids on leaves or buds or mysterious as when you see holes on the leaves of your plant. You will then need to do some investigating – examine the leaves, check the undersides of the leaves, go out at night with a flashlight etc. Once you identify the culprit, you can go to UC Pest Notes and read about its lifecycle. When does it appear? When is it actively feeding? Once you know that, you can find out if you can grow your crop so that it does not coincide with the insect’s active feeding time.

Three of the best examples of pests that can be avoided through timing are Aphids and Cabbage Loopers on cole crops such as broccoli, cauliflower and cabbage or Leafminers in Swiss chard. All three pests are active in warm weather and can be mostly or completely avoided by Bayside gardeners by planting these cool season crops in the fall or early spring. The plants thrive in cool weather and the pests are greatly reduced or non-existant at those times.

Selecting Disease Resistant (or Tolerant) Vegetable Varieties

For many years now, plant breeders have sought to produce crops – mostly hybrids - that can resist or tolerate common plant diseases. If you have a problem with a particular disease, you can minimize the damage and maximize your crop by selecting a resistant or tolerant variety. Resistant means that the plant will resist developing the disease while Tolerant means that the plant (if exposed) will develop the disease, but should produce a crop anyway. Resistant is better than Tolerant so look first for Resistant varieties.

Once again, it is important to correctly identify the disease problem before you select your seed variety. Common problems in Alameda County are Powdery Mildew, Verticillium Wilt, Fusarium Wilt, Rust, Nematodes, Fire Blight, Peach Leaf Curl and Sooty Mold. Refer to UC Pest Notes for more on each one. Check Here for more diseases in Alameda County.
Resistance is generally indicated on a seed packet or in a seed catalog by a letter code. For example, a V on a tomato seed packet means that the tomato is resistant to Verticillium Wilt.
A Partial Listing of Plant Disease Codes to look for is:
A Anthracnose
AB Alternaria Early Blight
B Bacterial Wilt
Fusarium Wilt Race 1
F2 Fusarium Wilt Race 2
LB Late Blight
N Nematodes
PM Powdery Mildew
R Common Rust
S Scab
TMV Tobacco Mosaic Virus
V Verticillium Wilt
W Common Wilt

Barriers, Traps and Protective Covers

If you can’t avoid pests through timing, the next thing to try is exclusion.
Barriers prevent the pest from reaching your plants. The number and type of barriers varies widely. They range from Copper Foil barriers for excluding snails and slugs to Sticky Traps you can hang in fruit trees to catch fruit flies to wrapping paper covered with a Sticky Substance such as Tanglefoot around a tree trunk to exclude the ants that protect colonies of scale and aphids on the tree. To be most effective, barriers need to be maintained and replaced regularly.
Traps also vary widely, from Pheromone Traps used to lure male moths to Yellow Sticky Traps which will capture a range of insects to Beer Baited Traps for snails and slugs. Again, you need to identify your pest and then find it in the Pest Notes Index and look for suggested traps for that pest.
Protective Covers can include row covers and hot caps that prevent the pest from reaching the plant. Insects such as cucumber beetles will feed on many plants and can spread disease from one plant to another via their mouthparts. To be effective, row covers need to be in place when the target insect emerges or hatches, so again you need to identify the pest and read about its lifecycle.  
Further Reading:
To Identify Pests and Diseases go to UC IPM
For a more complete discussion of traps and barriers for snails and slugs, see the Pest Note: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7427.html
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