It is well recognized that most specialty crops do not have sufficient herbicide coverage to provide commercially acceptable weed control. As a result, specialty crops generally have more complex and expensive weed control programs than agronomic crops. From the perspective of agricultural chemical companies, agronomic crops are much more attractive because there are so many more acres of agronomic crops like corn and soy than there are vegetable crops like broccoli and lettuce. When an herbicide is registered on a crop like field corn, which cover 90 million acres in the USA, a 10% market share means that the herbicide will be sold on 9 million acres and there is a plausible path to profitability for the chemical company. In contrast, a specialty crop like lettuce is grown on 261,000 acres, so it follows that a lettuce herbicide realizing a 10% market share will only be used on 26,100 acres, and the profitability potential very small compared to field corn.
There are significant costs and liability risks to registering a new herbicide in specialty crops. For example if an herbicide damages field corn, the registrant is perhaps liable for $700 per acre (Iowa State Univ. 2017). However, if an acre of lettuce is damaged by an herbicide then the liability may be $12,500 per acre (UC Davis, 2017). In other words, the risks of herbicide registrations in high value specialty crops far outweigh the benefits to registrants. Low market incentives for herbicide registration in specialty crops and increased liability risk are significant barriers for transfer of herbicide technology from major crops to specialty crops.
Automated weeders offer a glimpse into the potential for robotic technology to be used among agronomic crops and specialty crops. There are two dedicated intelligent intra-row cultivators on the market now, Robovator from Denmark and Steketee “Intelligent Cultivator” (IC) from the Netherlands. Both function by detecting crop row patterns and cultivating all around the individual crop plants with cultivator knives, i.e., intra-row cultivation. The Robovator and Steketee IC machines are early versions of automated weeders and there is considerable room for improvement. For example, they cannot differentiate crops and weeds, but rather they rely on crop recognition by row pattern. If there are many weeds then these machines cannot function well. Similarly, four different commercial lettuce thinners use machine vision to recognize the lettuce seedline pattern in direct-seeded lettuce, and selectively thin the lettuce to desired commercial stands. Lettuce thinners apply herbicides or caustic fertilizer solutions to kill selected lettuce plants. The potential for this lettuce thinner technology to be used for weed control is an active area of research. BlueRiver Technology, which developed its technology for lettuce thinning, was recently purchased by John Deere Co. – an example of technology flowing from a specialty crop, lettuce to an agronomic crop, cotton.
Intelligent cultivators have considerable advantage over herbicides in that they can be transferred among crops in the same way that tractors are used in numerous crops. For example, a tractor can be used in any crop provided it has the right row spacing, dimensions and horsepower to do the necessary task. The barriers for moving tractors among crops are much lower than for moving herbicides among crops. Similarly, there are very low barriers for movement of automated weeders among crops because they are not regulated in the same way as herbicides. Tractors have standardized features, such as a 3-point hitch, that allow them to be used in many crops and as such, the development costs of new tractors can be shared among a large number of farmers at low cost per unit. Similarly, a standardized field robot that can be used in many crops, and for many uses besides weeding, will allow the development costs to be shared among the many farmers that use the equipment at lower cost per unit. Because the barriers for the transfer of physical weed control devices among crops is low, the potential for their use in specialty crops is high.