It’s a bug-eat-bug world inside the Brown greenhouse

by Anna Henderson ’03

Visit the conservatory of the campus greenhouse and, in addition to the lush vegetation and tropical flowers and fruits, you are likely to notice the presence of ladybugs.

The introduction of specific predatory insects like ladybugs is creating a new indoor ecology in the conservatory while reducing insect pest populations.

Ladybugs, for instance, feed on aphids, small insects that appear in masses on the underside of leaves. Aphids have a piercing, sucking mouthpart to sip plant sap, causing leaves to deform and wilt.

A particular favorite of aphids is the taro plant, said greenhouse technician Brian Leib, who is responsible for setting up the new pest-prevention program.

“I’ll release 300 to 700 ladybugs at a time,” he said. “They are very flighty, so I release them early morning or late evening.” Ladybugs are the most visible predators, but several more discrete bugs – mealy bug destroyers, whitefly predators and insect parasites – are also being released.

“In a conservatory setting, there are always isolated bug problems,” said Leib. The bugs “come in on clothes, plants, and the wind.” Insect invaders “can destroy a greenhouse entirely,” he said.

There is a trend in greenhouses toward controlling insect pests instead of trying to eliminate them with chemical sprays, said Fred Jackson, greenhouse manager. Two decades ago, when Jackson began working in hothouses, the mindset was to eliminate all insects by spraying chemical pesticides weekly or biweekly, he said.

“It didn’t work because insects built up a resistance to sprays,” said Jackson. “Now we try to live with the insects.”

Clinton Morse of the University of Connecticut Greenhouse has employed the “bugs-eat-bugs” system since 1996. “The first thing that needs to be done is to determine what the pest tolerance is going to be,” Morse said. Because many greenhouse managers and users start off thinking that a zero-bug tolerance policy is necessary, “a re-education process” also is involved, he said.

Jackson and Leib are now working to find that balance, determining how many “bad” insects they and their plants can live with. One of the drawbacks to the switch is that “biology takes a while to have an effect,” said Leib. During the transition, he and Jackson have kept their options open for dealing with insect pests.

Alternatives are used only as needed, said Leib. They include chemical pesticides, insect growth regulators, oils and fungi. All have potentially negative environmental impacts. They could “poison groundwater, employees, visitors, wildlife, even hurt the plants,” he said.

“The greenhouse was good before, but now it is better,” said Jackson. “We always strive to get better and better. We still see some insects, but the ones we see are on the run.”

The conservatory, which is open to the public, is “like a plant museum with interesting shapes and forms of plants grown around the world,” Jackson said. The rest of the greenhouse complex consists of research-only hothouses, where pesticides are occasionally used to protect plant experiments.