Agriculture is under pressure from regulations, as well as environmental and economic issues. In 2013 there were also widespread labor shortages in the Salinas Valley. These issues put pressure on growers to adapt and resolve each of these problems. Fortunately, new technological developments can provide solutions to some of the issues that growers face. In 2013, four companies developed automated thinners for use in lettuce production (photos 1-4). These machines came at a fortuitous time for growers and provided one solution for dealing with labor shortages.
The thinners use a camera to capture images of the lettuce stand and a computer to process the images and make decisions on what plants to remove and which to keep (photo 5). Unwanted plants are removed with a spray material such as salt based fertilizer or acid based fertilizer. These materials provide good control of unwanted plants, but they do not work as well early in the morning when the plants are wet with dew (Table 1, photo 6). Shark was shown to be highly effective even when the plants are wet and a 24c registration is currently pending at the California Department of Pesticide Regulation for its use in thinning/weeding lettuce.
Ten to fourteen days following the thinning operation, a hand crew goes through the field to remove doubles and weeds that escaped the thinning/weeding operation. The speed with which this crew moves through the field is dependent on how efficient the thinning operation was conducted. One challenge for the automated thinners is to remove doubles. It is tricky for the machine to safely spray a lettuce plant that is close to the lettuce plant that it wants to keep; this is an area where the developers of the thinner machines are actively working to make improvements and growers are working to improve lettuce seed singulation.
