Cotton production is not entirely dependent on insect pollination, but
can be increased by bee visits to the cotton flower. In Brazil, this
bee-generated yield increase is poorly studied and, for this reason, is
ignored, especially in conventional plantations. In this production system,
soil preparation is mechanized and insecticide is intensively employed,
especially during flowering. These practices reduce bee nesting and foraging in
and around the cotton fields, and bee benefits may not be noticeable. On the
other hand, in organic farms, where mechanization and insecticide use are
minimized, the yield increase promoted by bees is evident and helps making this
production system economically viable for smallholding.
Loughnan, James D. Thomson, Jane E. Ogilvie, and Benjamin Gilbert
insects tend to visit single species of plants, but in some circumstances they
switch flower types within a foraging bout and therefore deposit mixed loads of
pollen on stigmas.In a few species, the
receipt of foreign pollen has been shown to depress fruit or seed set in the
recipient flower.This phenomenon is
termed “pollen allelopathy,” and the presumed mode of action is through soluble
chemicals leached from the pollen grains.
Read the whole summary in: English! Read the scientific
publication in JPE.
Non-native dandelions (Taraxacum officinale,
yellow flower heads) invade a subalpine meadow below Mt. Crested Butte,
Colorado, USA, where the study was performed.