Does a crop need insect pollination?
A standard method to determine whether a crop benefits from insect pollination is to compare the yields of plants that are grown under three different conditions: a) covered by nylon screen cages containing honeybee colonies; b) covered by cages to exclude insects; c) not caged. If cages are not available useful information may be obtained by bagging individual flowers or flower heads to exclude pollinating insects. Some of the bagged flowers must be hand-pollinated to find the maximum set possible under these conditions. Experiments must also determine whether the crops benefit from self- or cross-pollination. Cross-pollination is obviously needed when the sexes are segregated on different plants (for example melon) or by different periods of flowering of the same plant (for example avocado). Cross-pollination may also increase yields of plants that can be self-pollinated. Cross-pollination can only occur when the insect moves from one plant to another, and this usually happens on onl
