Strong, proven performance in the field is what makes a biorational product such as Bt such an indispensible tool in a grower’s arsenal against lepidopetran pests. However, experienced Bt users know that a major advantage of biorational products is their multi-faceted value proposition.

One easy way to remember the most widely accepted of these benefits is the “Three Rs of Biorationals”:

• Resistance Management
• Restricted Entry Intervals
• Residues

Resistance Management is the hallmark of a program that includes biorational products. As the pool of allowable conventional insecticides continues to shrink, resistance management is an even greater concern for growers than in years past. Researchers and extension specialists will tell you that once growers find an effective and affordable insect management product, it’s common for that product to become overused and for resistance to develop quickly. Rotation with an effective Bt product such as DiPel or XenTari is among the best ways for growers to keep conventional pesticides viable for the long term.
Restricted Entry Intervals (REI) add complexity to a grower’s harvest and labor management considerations. Here again, biorational products help make a grower’s life easier in that most biorationals (Bt included) have a 0-4 hour REI and no pre-harvest interval. This makes biorationals especially strong for late season applications.
Residues are gaining increased attention in an ever-more complicated regulatory climate, especially among growers who export their products. Pesticide and food regulators around the world have established unique Maximum Residue Limits (MRLs) for their countries or regions. Since fresh fruit and vegetable growers may or may not know where their crop will wind up, residues levels are critical. For this reason, biorational products stand head and shoulders above most other crop protection tools. Since the vast majority of biorationals exhibit no human toxicity, they are exempt from tolerance.

Because of some unique characteristics, biorationals provide growers with some valuable tools late in the season. Plant growth regulators such as Retain can delay harvest time in stone fruits, allowing flexibility in labor management. Delaying harvest can also increase yield – fruit on the tree can increase 1% of its weight per day. Depending upon the product and crop, plant growth regulators provide a variety of other benefits at harvest time, including enhanced fruit storageability, reduced pre-harvest fruit drop and improved skin finish.

Residue levels are becoming of increasing concern among consumers, and maximum residue levels have been significantly lowered, particularly in Europe. Most biorationals are exempt from residue limits, so they are safe to use very late in the season, providing protection for a crop close to harvest. Because biorationals have the shortest worker re-entry interval allowed by law under U.S. EPA standards, they are ideal to use for late season pesticide applications when timing of harvest is critical. Biorationals are important tools for greenhouse operators for the same reason, since pesticide applications are made in enclosed areas.

As the European Union clamps down on Maximum Residue Levels (MRLs), reducing them by as much as 50 percent in some cases, residue management on harvested crops has been a topic on many grower’s minds. Adding further complications to the issue is the fact that MRLs differ widely between all countries.

For example, the MRL on apple shipments of the commonly used fungicide, captan, is listed in the U.S. at 25 ppm, in China at 15 ppm, in Canada at 5 ppm, and in the EU at just 3 ppm. Similarly, MRLs for the insecticide carbaryl (Sevin) on apples are listed at 12 ppm in the U.S., while Canada will accept 5 ppm and the EU just .05 ppm. In some countries, especially the EU, the MRL is any detectable level for certain inputs. Although there is a standard, called the Codex Alimentarius, developed by the World Health Organization and the Food and Agricultural Organization of the United Nations, that sets recommended acceptable residue levels, its adoption is strictly voluntary. Some countries defer to the Codex, others set their own, much more restrictive standards, and still other countries do not have a list at all.

How do biopesticides help with this vexing problem? Simply put, most biopesticides are exempt from MRLs, giving growers a valuable tool in managing residue limits on their crops. If used exclusively, biopesticides eliminate the need to worry about the MRLs of the export market. More commonly, biopesticides are used in combination with conventional pesticides, but they can still significantly reduce residue because the total chemical pesticide load is decreased. In addition, using biopesticides at the end of the season provides crop protection without adding residue just before harvest and shipment.