Pheromone Revolution Hits Half Century Mark

HALF a CENTURY ago the PHEROMONE REVOLUTION commenced in earnest. German chemist Adolf Friedrich Johann Butenandt opened the floodgates as lead author of an article announcing the isolation and chemical identification of a sex pheromone female silkworm moths produce to attract male mates. Butenandt had already shared the 1939 Nobel Prize in chemistry for discovering human reproductive steroid hormones. So the 1959 article announcing the first pheromone in the monthly chemical science journal Zeitschrift für Naturforschung B (14B:283-4) attracted the attention of Rachel Carson and stimulated the efforts and imaginations of many others searching for insecticide-reducing alternatives.

HALF a MILLION virgin female silk moths were sacrificed over a span of almost THREE DECADES to identify that first sex pheromone, named bombykol because Bombyx mori is the scientific name of the Chinese silk moth of textile fame. In the past half century, thousands more pheromones have been identified, mostly from pest insects of economic interest. But also increasingly from beneficial insects providing biological control.

According to researchers like Jeffrey Aldrich at the USDA-ARS Chemicals Affecting Insect Behavior Laboratory (CAIBL) in Beltsville, MD, the potential applications of natural enemy pheromone and semiochemical research, such as herding beneficial insects into crop fields where they are needed, is still in its infancy. Projects include using pheromones to increase biocontrol by predatory spined soldier bugs (Podisus maculiventris). These beneficial stink bugs are capable of biologically controlling pesticide-resistant Colorado potato beetles, Mexican bean beetles, and cabbage and tomato caterpillars.

One idea is using pheromones to trap natural enemies, and then creating mini-insectaries by placing cages full of natural enemies into crop fields and landscapes. Predator production can be maximized with “an in-field nursery where we are putting these trapped bugs right inside of the (mesh) cage” over plants in the field, said Aldrich. “You pick a mesh size where the adults can’t get out, but when they lay eggs then the nymphs can walk out and start feeding on pest species in the vicinity.” In field tests, potato defoliation was reduced and yield significantly increased.

In bean field tests, spined soldier bug nymphs walked upwind towards an aggregation pheromone. In sequential plantings, this technique could be used by farmers to move or herd predators out of maturing fields into more newly planted fields. Pheromone technologies are also being explored to maximize biocontrol by minute pirate bugs, big-eyed bugs, tachinid flies, and other natural enemies.