Ag at Large: Bugs to the rescue

Photo courtesy of pixabay.com

Insects by the trillions called beneficials have been raised and released annually in California for the past 50 years or more as a significant means of pest control, especially for agricultural applications. The practice may need a special upgrade now to deal with the dreaded Asian Citrus Psyllid (ACP).

From its beginning as a commercial method for controlling damaging predator insects, the releases have enjoyed enthusiastic participation in California’s citrus industry. Orange, grapefruit and lemon growers don’t need to be persuaded of its effectiveness and the need to intensify it. Growers of many other crops agree.      

The worldwide search for insects to raise, those that will be effective in reducing populations of “the bad guys,” has been a real life Indiana Jones adventure for some of the most qualified and energetic entomologists in California. Most of them have been associated with the University of California.

The search has almost always gone beyond the insect itself to the food it needs to exist. Discovering a rare beneficial insect in Timbuktu is one thing, learning to supply its sustaining diet is quite another. And the specialists must determine if that favorite diet can be produced or procured in sunny California.       

One of the earliest insectaries in California was established in the 1960s in Fillmore. It offered vial after vial of the hungry parasitic mini wasp aphytis melinus and other species that growers or their pest control advisors can release at strategic times and locations. In the open the beneficials pursue an expanded diet, and that usually includes predator insects such as red scale crunching leaves in a vineyard, orchard or row crop field.

Another approach involves capturing, rearing and neutering by radiation the males of a given species under tightly controlled conditions. When these sterile males are released in a crop environment, they mate with females of the species, leading to an absence of offspring and an immediate reduction in the population of the “bad” bugs. It’s a kind of birth control on a massive scale.

With the ACP threatening California’s multi-billion dollar citrus industry, growers and other industry leaders are examining ways to expand the use of insects that can help control it.  Insectaries now number more than a dozen in California, several of them specializing in the production of insects that will eat or otherwise destroy the ACP.

Releases of these beneficial insects are on the increase, particularly in Riverside County, and mostly in residential areas. To many residents of Riverside County, a citrus tree in the backyard is a sign of belonging, a kind of status symbol. Hungry ACPs have found the trees, and have invited friends and family to join them. Any of them can be expected to carry the huanglongbing virus that so devastates citrus trees, the one transmitted by the ACP.      

To their immense credit, residents in the residential areas where the insect has been detected are cooperating with researchers and pest control practitioners who arrive with vials of beneficial insects or in some cases, a spray material. Containing rather than eliminating the ACP is their goal for the present. Eradication may be down the road.      

With support from citrus growers throughout California, the rearing of beneficial insects expected to attack the ACP is moving ahead rapidly. An insectary in Riverside is being utilized by the California Department of Food & Agriculture(CDFA). Millions of these are expected to be released in the Los Angeles Basin this year.

Citrus production receives special attention at the University of California, Riverside.  Entomologists and other specialists there maintain close observation of progress at the neighboring CDFA insectary. A special insect rearing project is ongoing at Cal Poly in San Luis Obispo, involving trees enclosed by nets with measurable insect activity taking place beneath.

We know of the benefits offered by bees, and we’re learning about the help we can expect from other insects we call beneficials.