Humans have co-existed with leeches for so long, according to Siddall, that just about every language has a word for leech. 3. theyâve made a comeback in medicine.
The lettuce aphid is a problem worldwide and has recently become problematic in the western United States and Canada (Liu and McCreight 2006; McCreight 2008). However, the first three species of aphids listed above are most economically damaging in Florida (Nuessly and Webb 2010). Although heavy aphid pressure can stunt plants, the major problem aphids cause is head contamination, which makes lettuce unmarketable.
Aphids are distributed worldwide, but are most common in temperate zones. In contrast to many taxa, aphid species diversity is much lower in the tropics than in the temperate zones. They can migrate great distances, mainly through passive dispersal by riding on winds.he removal of sap creates a lack of vigour in the plant, and aphid saliva is toxic to plants. Aphids frequently transmit disease-causing organisms like plant viruses to their hosts. The green peach aphid, Myzus persicae, is a vector for more than 110 plant viruses.