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.
The most serious damage to soybean plants can occur during the reproductive growth stages, and aphid populations should be monitored most intensively during this time. Aphid sampling consists of whole-plant counts of affected plants with a threshold of 250 aphids/plant. Count 20-30 plants/field and be sure to sample the entire field. Focus your counts upon the undersides of leaves initially, though aphids will spread throughout the canopy when populations grow.