IRAC Susceptibility Test Method 002

All Stages of Development
Approved Version 3 June 2009

Materials

Jars/containers for holding shoots, beakers or glass jars (ca. 100-ml capacity) for test liquids, 1-ml disposable plastic syringes for liquids or weighing balance for solids, hand lens or binocular microscope, fine pointed brush or cocktail stick, maximum/minimum thermometer.

Methods

  1. Collect shoots infested with immature stages. The best time is when 1st and 2nd instar nymphs of the second generation are present which is late May (Italy) or early June (Central Europe). It is important to treat before much honeydew is produced.

  2. Place the shoots in water to keep them fresh.

  3. Using a good hand lens or a binocular microscope, count the number of live nymphs. Remove any adults.

  4. Agitate test liquids and then dip shoots for 5 secs using five or six shoots at each rate. Dip equal number of control shoots in water only.

  5. Keep shoots in water in an area where they are not exposed to direct sunlight or extremes of temperature. Record maximum and minimum temperatures.

  6. After 24 h using a hand lens or binocular microscope, record number of surviving nymphs by checking their ability to show co-ordinated movement in response to a touch with a small brush or cocktail stick

  7. Express results as percentage mortality and correct for untreated mortality using Abbott’s formula. Untreated mortality should be recorded.