You may have noticed that some of your favorite carrot varieties have become temporarily unavailable or backordered. This issue is being caused by a surging population of a pest that has a particular taste for Umbellifers, the family of plants that carrots belong to. Lygus Bugs, an insect categorization with over 40 unique species, are common across North America with a notorious reputation for causing significant crop damage and loss of viable seed.

Russ Ottens, University of Georgia, Bugwood.org
The Scope

There are 4 major Lygus Bug species that have been identified in North America as pests. These include the European Tarnished Plant Bug, Tarnished Plant Bug, Western Tarnished Plant Bug, and the Lucerne Plant Bug. Lygus Bugs are pests at all stages of development, from nypmh to maturity, and it has even been determined that Lygus Bugs are most dangerous to carrot seed crops in their nymph stage. The nymphs and adults feed on all parts of their host plants, using their piercing and sucking mouth parts to derive nourishment from the plant tissue. While they feed, they also release a toxic saliva that causes even more damage to the developing plants.

While they commonly feed on all parts of the plant, they are particularly hazardous to the plant's reproductive systems, focusing their feeding on buds, fruiting bodies, flowers and seeds. A serious infestation, one Lygus Bug per flower or seed head, can cause total crop loss. The effects of these invaders are seen as 50-100% loss of seed set and maturation and even the development of embryo-less seed.

When feeding on buds and flowers, visible signs of damage can be seen and seed will be destroyed during development. When the petals have dropped and the seeds are being formed, damage can be much more difficult to see and can result in the production of embryo-less seed which may be harvested from the seed crop undetected. It becomes very important to protect the developing carrot seed at this time, as what ends up being harvested can have a very low germination rate.

The Challenge

 

Unfortunately, the issue of Lygus Bugs in organic carrot seed production is growing. It is becoming more difficult to find land that is not already supporting a serious population of the harmful Lygus species. Land that is already in carrot seed production struggles to manage the populations with organic measures. Row cover can be used at certain times, but is only partially helpful in controlling the pests' access to the crop and does not reduce pest numbers. It is also cumbersome as it must be removed for certain periods of the breeding and reproductive processes.

Organic growers have fewer tools to manage pests species as they often use a limited selection (if any at all,) of organic approved pesticides. Even in conventional farming, the continued use of pesticides has resulted in some resistance in Lygus Bugs. Pyrethrin, the strongest insecticide allowed under the National Organic Standards guidelines, can be used but is not wholly effective. It has been determined that Lygus Bugs need to be sprayed at least 3 times at key moments in the season. This is to help stave off the momentum of their growing populations as a result of the 2-3 generations that can cycle through to maturity in one season.

Another factor that seems to be contributing not only to the spread of Lygus Bug populations, but to their ability to cause harm, is variability in climate. Lygus bugs can go from nymph to adult in just 12.5 days when conditions are warm (90 degrees and up.) As regions continue to warm and experience periods of unseasonable weather and drought, Lygus Bugs are spreading and growing in numbers. In areas where drought is a new issue, Lygus Bugs can be especially severe.

The Consequences
Scott Bauer, USDA Agricultural Research Service, Bugwood.org

 

All of these difficulties have serious impacts on organic carrot production. It is harder than ever for carrot breeders to have access to land that is not impacted by the Lygus Bug. Carrot seed that is brought in to High Mowing will sometimes appear normal, but will show a low germination rate when tested due to the presence of embryo-less seed. There is and will continue to be a reduced availability of carrot varieties, particularly hybrids, as these issues continue.

The Path Forward

The path forward may be wrought with challenges, but as you well know, the creativity and resilience of organic growers is profound. As adversity in the field continues, seed growers across North America, who are dedicated to providing high quality organic carrot seed to farmers and gardeners, are working tirelessly to raise successful crops and innovate strategies for success. The best thing we can do as happy recipients of their hard work is to continue buying organic carrot seed. These seed producers need our support now more than ever and here at High Mowing we will do our part to promote this essential work and bring their high quality offerings to our growers through our website and catalog.

To learn more about how Lygus Bugs can impact your own farms and gardens, read more on our blog post: Pest Management: The Lygus Bug.

 

References

Seed Piercing Bugs on Apiaceae Seed Production - Cleide Dias, Entomology Researcher - Bejo Seed Production Research