How to Manage Pests

UC Pest Management Guidelines

Tomato

Potato Aphid

Scientific Name: Macrosiphum euphorbiae

(Reviewed 12/13, updated 12/13)

In this Guideline:


Description of the Pest

The potato aphid has both a pink and a green color biotype. This aphid is much bigger than the green peach aphid with a more elongate body shape and is generally found on the terminals of tomato plants later in the season than green peach aphids. It is also considered to be more damaging.

Damage

High potato aphid populations can distort leaves and stems, stunt plants, and cause necrotic spots on leaves. These aphids also secrete a large amount of honeydew that promotes development of sooty mold on foliage and fruit. Plants are particularly susceptible to yield losses from high infestations during the period from 6 to 8 weeks before harvest. Yield losses from equally high aphid populations decline substantially as harvest approaches, unless aphid densities are reducing leaf area enough to permit sunburn.

Management

Monitor potato aphids from 6 to 8 weeks before harvest as well as the level of parasitism and the activity level of predators. Treatments may be necessary if natural enemy activity is low and populations are increasing.

Biological Control

Naturally occurring parasites and predators of the potato aphid are common and can provide control. Monitor the proportion of aphid mummies relative to unparasitized aphids and the numbers of predators such as lady beetles, lacewing larvae, and syrphid larvae. 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.

Tolerant Varieties

There is considerable difference in tomato variety susceptibility to potato aphid feeding. Varieties containing the Mi gene, which confers resistance to nematodes, have been reported to be more tolerant of potato aphid infestations. However, this resistance no longer appears to be as effective as it once was, particularly against the pink form of the potato aphid.

Organically Acceptable Methods

The use of tolerant varieties, biological control, and sprays of herbal oils, pyrethrin, or insecticidal soap are acceptable for use on an organically certified crop. Repeated applications may be necessary for control.

Monitoring and Treatment Decisions
  1. Monitor potato aphids from bloom to early fruit set by picking the highest open flower on 30 plants selected at random throughout the field.
  2. Record on a monitoring form (PDF) the presence or absence of potato aphids on each leaf, while noting natural enemies.
  3. Treat if 50 to 60% or more of the leaves are infested.
  4. During late fruit set, combine monitoring for potato aphid with monitoring for tomato fruitworm :
    1. Pick the leaf below the highest open flower on 30 randomly selected plants from throughout the field.
    2. Record observations on a monitoring form (PDF)
    3. Consider a pesticide application. If 50% of these leaves are infested during the period 6 to 8 weeks before harvest, the resulting loss is about 1 ton per acre, and a pesticide application should be made.

Good spray coverage is important in controlling high populations. Ground sprays using hollow-cone nozzles or air-assist sprayers will provide the best canopy penetration. Higher spray volumes are also helpful.

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. SPIROTETRAMAT
  (Movento) 4–5 fl oz 24 1
  MODE-OF-ACTION GROUP NUMBER1: 23
 
B. FLONICAMID
  (Beleaf 50SG) 2.8 oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 9C
 
C. THIAMETHOXAM
  (Actara) 2–3 oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
D. IMIDACLOPRID
  (Admire Pro) 7–10.5 fl oz 12 21
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Most often applied in drip or trickle irrigation water. Can be used preventively as a systemic in areas with chronic infestations. Apply as a sidedress within 4 inches on either side of plants and incorporate to a depth of 2 to 3 inches. Treat at first bloom up to 8 weeks before harvest. Apply sufficient water following application to move into the root zone of the plant. Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
E. PYMETROZINE
  (Fulfill) 2.75 oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 9B
 
F. ACETAMIPRID
  (Assail 70WP) 1.2 oz 12 7
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
G. DIMETHOATE      
  (Dimethoate 2.67EC) 1.5 pt 48 7
  (Dimethoate 400) 1 pt 48 7
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not use this product if leafminers are present because it is destructive of their parasites. Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
H. THYME OIL#
  (Proud) Label rates 0 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Short residual material. Do not use if sulfur was applied recently or will be in the near future.
 
I. PYRETHRIN#
  (PyGanic 1.4ECII) Label rates 12 0
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Short residual material that provides moderate control with repeated applications. Always buffer to pH 5.5 or lower.
   
J. ROSEMARY OIL + PEPPERMINT OIL#
  (Ecotrol) 1–1.5 pt 0 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Short residual material. Apply with organic spreader and sticker. Do not use if sulfur was applied recently or will be in the near future.
   
K. INSECTICIDAL SOAP#
  (M-Pede) 2.5 oz/gal water 12 0
  MODE OF ACTION: A contact insecticide with smothering and barrier effects.
  COMMENTS: Soaps provide less than 50% control of potato aphid, but can be used to reduce numbers, particularly when parasite activity is noted.
 
** See label for dilution rates.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment until harvest can take place. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470

Insects and Mites

E. T. Natwick, UC Cooperative Extension, Imperial County
C. S. Stoddard, UC Cooperative Extension, Merced and Madera counties
F. G. Zalom, Entomology, UC Davis
J. T. Trumble, Entomology, UC Riverside
G. Miyao, UC Cooperative Extension, Solano and Yolo counties
J. J. Stapleton, UC IPM Program and Kearney Agricultural Center, Parlier (false chinch bug)
Acknowledgments for contributions to Insects and Mites:
C. G. Summers, Entomology, UC Davis and Kearney Agricultural Center, Parlier
C. F. Fouche, UC Cooperative Extension, San Joaquin County
N. C. Toscano, Entomology, UC Riverside

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