The risk of moving seeds of branched broomrape on field equipment has three main components:
Broomrape plants present in the field or broomrape seed present in the soil.
- Broomrape plants are difficult to detect, particularly at low infestation levels. Broomrape seeds are extremely small and difficult to detect with the naked eye; once mixed into soil or plant debris, they become virtually impossible to see. Therefore, risk reduction efforts are focused into three categories: fields known to have broomrape or at high risk (“high risk” field), fields not known to have broomrape but are in the area where fields have been reported (the designated zone), and fields not near known infested fields (out of the designated zone). However, it is critical to remember that “lower risk” is not the same as “no risk” and precautions are encouraged to protect the individual operations and the industry at-large.
Equipment can accumulate soil or plant debris.
Broomrape plant material and seed move in debris that is on or in equipment. Thus, risk is highly correlated to the amount of debris and soil on the equipment and this includes both soil-contact parts of the equipment (tires, blades, knives, etc.) as well as any other part of the machinery where soil, dust, or plant material accumulate.
Large, complex equipment such as harvesters typically accumulate more debris than simpler equipment, but all field equipment can accumulate soil and plant debris and is a potential risk. This fact is why broomrape risk reduction starts with physical cleaning of equipment to reduce debris loads; it reduces total debris (potentially harboring broomrape seed) and facilitates better sanitation because debris physically and chemically interferes with many sanitizing chemicals.
Equipment moves among fields and drops soil/debris potentially contaminated with broomrape seed into an uninfested field.
This risk component is complicated because debris-load, number of sites visited, and distance all impact the risk of moving broomrape seeds within the processing tomato production system.
Spread of seed within an already-infested field or from an infested field to a non-infested field could easily occur on many kinds of equipment. While equipment with high loads of soil and/or plant debris represent the most significant risk of field-to-field movement within a region lower-debris equipment (sprayers, vine trainers, truck tires, or worker’s boots) are also potential sources of local spread.
An additional risk in the highly mechanized processing tomato industry are operations and personnel that enter many fields during the course of a season, a week, or even within a day (e.g. harvest trailers, field scouts, labor crews, crop consultants). Even if carrying relatively low debris loads, this type equipment or activity could be sources of significant risk of both short- and long-distance movement of seed because of the distance and number of fields visited.
