Petri dishes (9-cm diameter), plastic bags, cotton wool, untreated leaves, small forceps, fine pointed brush or cocktail stick, 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, maximum/minimum thermometer.
Sample apterous aphids by collecting infested leaves, selected at random from several plants. The leaves may be transported and held in plastic bags.
Collect some non-infested, untreated, leaves or remove aphids from leaves using a small brush before treatment.
Prepare appropriate test dilutions of formulations in water. The use of a wetter is not recommended.
Agitate test liquids and then dip non-infested leaves for 5 secs, five leaves per treatment. Dip five control leaves in water only.
Allow surface water to dry from leaves before placing them individually in Petri dishes and infesting each leaf with 20 adult aphids. The aphids can be transferred using a small pointed brush (with volatile insecticides it may be necessary to ventilate the Petri dishes by piercing the lids with a hot wire).
Place a small piece of damp cotton wool around the petiole of each leaf.
Store Petri dishes in an area where they are not exposed to direct sunlight or extremes of temperature. Record maximum and minimum temperatures.
Using a hand lens or binocular microscope assess mortality after 24 h by checking each aphid’s ability to show co-ordinated movement in response to a touch with a small brush or cocktail stick.
Express results as percentage mortality and correct for untreated mortality using Abbott’s formula. Untreated mortality should be recorded.