- Ideally, 50 trees should be sampled in each orchard. However, examining such large numbers of trees is time consuming and is unlikely to be economically viable. A minimum of 10 trees, preferably 20, should be assessed per orchard.
- If trees are small, sample more trees per stopping place to give a volume of canopy roughly equivalent to 3 x 3 x 2 metres.
- If a particular pest or disease is clearly over the threshold, assessment for that pest or disease in the particular orchard can be curtailed. However, it is important to check that this is not just an isolated patch.
- Bias should be avoided by taking samples systematically. For example, fix your eye on a particular branch and sample the nearest truss/branch/leaf on the right or left of the one you selected. This avoids picking out or avoiding obvious damage.
- Take successive samples from the north, south, east and west segments of the tree, inside and outside the canopy.
It is very important to maintain general vigilance for signs of pests or diseases as you walk through the orchard.