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How to Manage Pests

UC Pest Management Guidelines

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Tomato

Tomato

Monitoring for Potato Aphid and Tomato Fruitworm

(Reviewed 1/07, updated 1/07)

In this Guideline:

Start sampling for potato aphids 6 to 8 weeks before harvest and continue for 4 weeks. Start sampling for fruitworm eggs after adults are trapped in pheromone traps in late July or early August and continue through harvest.

HOW TO MONITOR (View photos of potato aphids and fruitworm eggs)

  1. Pick the leaf below the highest open flower on 30 plants selected at random throughout the field.
  2. Record presence or absence of potato aphid on each leaf. Also note natural enemies.
  3. Count fruitworm eggs on each leaf, noting whether eggs are white (healthy) or black (parasitized).
  4. Assess egg parasitism for fruitworm by counting the number of black (parasitized) eggs and compare them to the number of white eggs in the table below. The adjusted treatment letter "T" indicates the ratio at which treatment is recommended. If no black eggs are recorded, collect and observe white eggs for 48 hours and subtract those that turn black due to parasitism.
    5. No. of black eggs Number of white eggs
    4-8 9 10 11 12 13 14 15
    0
    T
    T
    T
    T
    T
    T
    T
    T
    1
     
    T
    T
    T
    T
    T
    T
    T
    2
     
     
     
    T
    T
    T
    T
    T
    3
     
     
     
     
    T
    T
    T
    T
    4
     
     
     
     
     
    T
    T
    T
    5
     
     
     
     
     
    T
    T
    T
    6
     
     
     
     
     
    T
    T
    T
    7
     
     
     
     
     
     
    T
    T
    8
     
     
     
     
     
     
    T
    T
    9
     
     
     
     
     
     
     
    T
    10
     
     
     
     
     
     
     
    T
  5. Record observations on a monitoring form. (124KB, PDF)
  6. Treat if monitoring shows that thresholds have been exceeded as outlined below.

TREATMENT THRESHOLDS

Tomato fruitworm Potato aphids
  • If less than 3 eggs are found, stop sampling.
  • If 3 or more eggs are found in 30 leaf-sample, sample 30 more leaves.
  • If 50% of leaves are infested, treatment may be warranted.
  • If the proportion of mummies is increasing or predators appear to be gaining control and aphid populations are not yet damaging, avoid sprays that will disrupt these natural enemies.
  • If less than 5 eggs found in second 30-leaf sample, stop sampling.
  • If 5 or more eggs found in second 30-leaf sample, assess egg parasitism to see if treatment is warranted.

IMPORTANT LINKS

PDF: You need Adobe Acrobat Reader version 5 or later to view or print this PDF. If this software is not installed on your computer, you can download a free copy of Acrobat Reader.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
General Information
F. G. Zalom, Entomology, UC Davis
E. M. Miyao, UC Cooperative Extension, Yolo County

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