How to Manage Pests

UC Pest Management Guidelines


Selecting the Field

(Reviewed 1/07, updated 1/07)

In this Guideline

Tomatoes planted in fields infested with tomato pests or fields with poor nutrient balance will suffer yield loss. Choose fields for tomato planting carefully, taking into account the field's cropping history. Also take into account pest problems that may originate in adjacent crops or fallow ground. Do these areas harbor pests of tomato such as root knot nematode, potato tuberworm, or problematic weeds? Many weed problems can be reduced by not planting tomatoes in fields that are severely infested with difficult weeds such as nightshades, field bindweed, nutsedge, and parasitic dodder. If this is unavoidable, treat weed infestations before planting (see SPECIAL WEED PROBLEMS).

Use the information below when selecting fields for tomato planting. Well-chosen fields can result in fewer pest problems.

Assay soil and water

  • Nutrient levels. Check for excessive salt and boron, and other mineral imbalances.
  • Soil pH. Tomatoes grow best at pH 6.0 to 7.5.
  • Herbicide residues. Residues may inhibit seedling growth. Perform soil herbicide bioassay.
  • Identify soil type. Tomatoes can grow in a variety of soil types, however, heavy clay soils require very careful water management and are generally less desirable. If possible, choose a field with deep, uniform loamy soil. Sandier soils usually have higher root knot nematode populations than soils that are more loamy. Avoid fields with large sandy streaks. Major variations in soil type within a field make application of herbicides difficult because rates must be adjusted for soil type.
  • Check irrigation water. If the quality of the irrigation water is unknown, assay for pH, salinity, and specific ion toxicities.
  • Root knot nematodes. Assay for nematodes before planting tomatoes if they have been a problem in a previous crop.

Check records

  • Agronomic information. Determine past tomato varieties that have been planted including their planting and harvest dates and yields. See if the field has supported successful production.
  • Cropping history. Identify previous crops that are known hosts of tomato pests.
  • Surrounding crops and areas. Check for cultivated crops such alfalfa, cotton, or safflower that harbor lygus, which damages tomato fruit. Check alfalfa for armyworms, cutworms, darkling beetles, whiteflies, and tomato pinworm. If pinworm is found, get rid of solanaceous weeds that may harbor them.

Check previous crop. Determine if pest problems such as garden symphylans, pinworms, potato tuberworm, nematodes, Fusarium or Verticillium wilt, dodder or other weeds, that might carry over to a new tomato crop were present in the previous crop(s).



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470

General Information

R. M. Davis, Plant Pathology, UC Davis
T. K. Hartz, Plant Sciences, UC Davis
W. T. Lanini, Weed Science/Plant Sciences, UC Davis
E. M. Miyao, UC Cooperative Extension, Yolo County
C. J. Rivara, Calif. Tomato Res. Institute
F. G. Zalom, Entomology, UC Davis

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