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UC Pest Management Guidelines


Potato psyllid nymphs.

Potato

Potato Psyllid

Scientific Name: Bactericerca (=Paratrioza) cockerelli

(Reviewed 8/07, updated 5/08)

In this Guideline:


DESCRIPTION OF THE PEST

Potato psyllids look like small cicadas, about 0.08 inch (2 mm) long. They are related to aphids and leafhoppers. The adult has clear wings that rest rooflike over the body. Although predominantly black, the potato psyllid does possess white markings. The first abdominal segment shows a broad white band, the last segment has an inverted white "V". Psyllids jump quite readily when disturbed.

The football-shaped eggs are extremely small, slightly larger than leaf hairs, and on a short stalk. They are usually on the underside of the leaf along the edge and in the upper plant canopy. A 10X hand lens is required to see them.

Psyllid nymphs look like immature soft scale or whiteflies. Unlike whiteflies, when disturbed, they move quite readily. They are flat and green with a fringe of short spines around the edge. The immatures go through five instars in as little as 13 days.

Psyllids used to be an occasional problem in California in certain years when they would migrate into the state from Mexico. In recent years, however, a more invasive form of the species has been found in California that has the ability to overwinter in parts of southern California. Potato psyllid now occurs on a yearly basis in these areas and has become a chronic problem.

DAMAGE

Damage is caused by a toxin that the immatures produce when they feed. The toxin causes a plant response known as psyllid yellows. Symptoms include an upward curling of leaflets nearest the stem on the top part of the plant. As the disease establishes itself, this symptom becomes more evident. Plant yellowing is the most common symptom. The yellowing (in some varieties, purpling) is initially found on the leaf edges.

Severe symptoms include overall yellowing with enlarged nodes, development of clusters of small leaves in the axillary buds that appear rosetted, and the formation of aerial tubers. Internodes are shortened and the plant eventually is dwarfed and appears pyramid shaped. The nature of psyllid yellows is unlike a virus. (Do not confuse psyllid yellows with the symptoms of calico virus. Symptoms of calico virus are not uniformly distributed and leaf rosetting is not present.) If the immature psyllids are removed from the plant, the progression of the disease will stop. As few as three or four nymphs per plant can produce symptoms but more are needed for severe symptoms.

Psyllids also vector an organism that is responsible for a condition known as zebra chip. The organism causes sugars to accumulate in areas of the tuber instead of starch; affected tubers have dark lines throughout the entire length. In chipping varieties, these areas turn black when the chips are fried, creating a black, striped effect that gives rise to the name "zebra chip". Infested plants produce fewer tubers. Yield losses from 20 to 50% have been reported. Tubers that are produced on plants attacked early in development will prematurely sprout in storage.

MANAGEMENT

Use yellow sticky traps to detect the presence of potato psyllid and initiate leaf sampling. Currently leaf sampling methods and thresholds are still being developed for this pest. It is recommended that the undersides of leaves be examined for nymphal stages. Because potato psyllid nymphs can be difficult to see on a potato leaf, planting a few pepper or bean plants in the field can provide an easier way to detect the nymphs. Bean, and especially pepper, plants have smooth leaves and are readily infested by the psyllids, making it easier to detect them on these crops than on potato plants. Keep records of your sampling results (example form—108 KB, PDF).

Potato fields in areas where the psyllid is known to occur should be treated at planting with imidacloprid. During the growing season, if monitoring indicates that populations are present and there is an average of 1 to 2 psyllids/leaf or 10/plant, additional treatment may be warranted.

Organically Acceptable Methods
Sprays of the Entrust formulation of spinosad are acceptable to use on an organically certified crop.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and environmental impact Not all registered pesticides are listed. Always read label of product being used.
 
AT PLANTING
A. IMIDACLOPRID
  (Admire Pro) 5.7–8.7 fl oz 12 0
  MODE OF ACTION: A neonicotinoid (Group 4A)1 insecticide.
  COMMENTS: Apply at planting as a side dress or through drip irrigation. Does not harm most beneficials. To reduce the potential for the development of resistance, avoid the use of neonicotinoids both as a soil and a foliar application on the same crop.
 
GROWING SEASON
A. ABAMECTIN*
  (Agri-Mek) 0.15EC 8–16 fl oz 12 14
  MODE OF ACTION: An insect growth regulator (Group 6)1 insecticide.
  COMMENTS: An insect growth regulator that is not harmful to most beneficials.
 
B. SPIROMESIFEN
  (Oberon) 2SC 8–16 fl oz 12 7
  MODE OF ACTION: A Group 231 insecticide.
  COMMENTS: Do not exceed two applications/crop or make applications at less than 7-day intervals.
 
C. SPINOSAD
  (Entrust)# 1.5–3 oz 4 7
  (Success) 4.5–6 fl oz 4 7
  MODE OF ACTION: A Group 51 insecticide.
  COMMENTS: Do not exceed 21 fl oz of Success or 6.5 oz of Entrust/acre/crop.
 
** 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 to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically certified 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: Potato
UC ANR Publication 3463
Insects
L. D. Godfrey, Entomology, UC Davis
D. R. Haviland, UC Cooperative Extension, Kern Co.

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