This observation came from helping some first-graders grow beans in a school garden: After the bean seeds sprouted and the starts grew 6 to 12 inches high, they wilted and died. How come?

The short answer is the bean fly maggot. The long answer involves a bit more entomology, soil science and botany.

Sometimes when gardening in Hawaii it can feel like we need a college degree in science to be successful. A successful gardener will take the time to learn about a plant before planting it. A great resource is the University of Hawaii College of Tropical Agriculture and Human Resources (CTAHR), which provides cooperative extension agents like myself to share knowledge with the public through publications, programs and other resources on home gardening.

A great trick to get information quickly is to type the plant or pest name and “CTAHR” into your online search engine. This will pull up local information about your plant or pest. For this topic you can try typing “home garden bean” and “CTAHR.” You can also try “bean fly” and “CTAHR.”

The CTAHR publication for this topic is “Home Garden Beans,” which lists information on seed selection (which type of beans grow best in Hawaii soils), preparing the soil, irrigation requirements, planting instructions, insect management and harvesting tips. Under the insect management section, we find that a common pest associated with home garden beans is the bean fly.

“Gardeners may find several pests on beans,” the publication states. “The bean fly lays eggs on the first leaves shortly after germination, and the maggot tunnels down the stem to the first node. The damage thus caused to the plant’s vascular system results in wilting and dying of the top of the plant.”

Knowing the life cycle of this insect is crucial. To prevent damage, gardeners must prevent the adult fly from laying an egg on the leaves. This can be done by practicing exclusion, such as using a fine netting around the young plants, or by painting an insecticide such as neem oil on the surface of the young bean leaves.

With further practice growing beans in school gardens, I learned that some plants can be saved after the damage is done. At the site where the maggot exits at the first node, soil can be hilled up around the wound. This encourages root growth and will provide more stability to the young plant.

Gardening can yield new ideas and learning experiences, especially when it doesn’t work the first time.

Jayme Grzebik is a Cooperative Extension Agent with CTAHR on the island of Oahu. She can be reached at grzebik@hawaii.edu.