Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Many of the food borne illness outbreaks in produce can be traced back to issues with wildlife intrusion. Wildlife droppings (fecal matter) can be a direct source of E. coli or Salmonella contamination in produce and irrigation water contaminated with wildlife fecal matter can serve to inoculate large areas of fields with these pathogens.
Wildlife serve as natural reservoirs of these pathogens and wildlife can move pathogens from field to field, or water source to water source. Major wildlife of concern for field contamination in our region include deer, waterfowl (geese particularly), and gulls. Secondary sources of concern would be groundhogs, rabbits, voles, other small mammals, and amphibians. In packing houses the major concerns are roosting birds and rodents.
Wildlife management in vegetable and fruit fields can be difficult. Growers should do a risk assessment of all their fields each year in regards to wildlife and match fields according the type of produce being grown. High risk produce such as leafy greens, tomatoes, and muskmelons should go in fields with the least signs of wildlife intrusion. Lower risk produce such as sweet corn would be more appropriate for other fields with more wildlife activity.
A major part of managing risk with wildlife is doing preharvest assessments. When doing a preharvest assessment, growers should look for wildlife intrusion and flag all areas where wildlife activity has been found. These areas and a buffer area surrounding them should not be harvested. In tree fruits, no fruit drops should be harvested.
In high value crops such as fruit, fencing and netting may be desirable to reduce wildlife intrusion (and damage to crops). Scaring devices and repellents, while not always effective, may also have a role in reducing wildlife activity in some crops. Damage permits for deer hunting can serve to reduce populations on some farms.
In surface water irrigation sources, efforts should be made to discourage wildlife, particularly during the irrigation season. Fencing and scaring devices should be considered where practical. Where high risk produce is being grown, growers should assess the risk of wildlife contamination of surface water used for irrigation. High frequency water testing for indicator E. coli should be done on surface water sources with high risk of contamination by wildlife. Treating water may be an option where contamination risk is high.
Eliminating wildlife habitat has also been considered as a control measure. However, this must be weighed against conservation benefits of these habitats.
In packing houses, active pest management programs should be in place. Eliminate roosting areas for birds in packing areas. Active rodent control programs should also be in place.