Microbials and a New Botanical for Lisianthus Disease Management

In the spring of 2013, the ASCFG funded a proposal to study the efficacy of low toxicity materials applied to prevent botrytis gray mold on lisianthus. Thea Folls had reported that in prior years serious losses due to botrytis took place in her lisianthus. Jana Lamboy, ASCFG member and a retired plant pathologist, volunteered to monitor the project, since she also grows lisianthus and worked with management of botrytis with microbial products on several hosts in the past. The grant paid for the materials and for travel, since the two participating growers live 40 miles apart.

The main trial took place at Folls Flower Farm in Owasco, New York, where Actinovate was applied to all seedlings that made up two thirds of the trial. One third consisted of transplanted purchased plugs. Actinovate, Regalia, and Serenade were applied at transplanting and then regularly during the season from early May until July 26. The treatment plots were marked off in the row with three replications, 30 plants per treatment block. The project relied on locally available botrytis spores, with no inoculated control since the entire crop was destined for sale. At Hastings Field in Geneva, compost tea prepared from Worm Power vermicompost was applied monthly to all the lisianthus, which was grown from purchased plugs.

At Folls Flower Farm, regular applications of water and liquid fertilizer with a drip line supplemented the initial application of composted horse manure tilled in at the beginning of the season. Plants were lightly mulched with straw after the soil warmed. Jana visited Thea in May, June, July, and August to observe symptoms and survival rates, and document the health status of the crop at Folls Flower Farm. It was a very successful crop, with three strong beautiful stems from each plant harvested to date.

Botrytis did not appear in the crop at either farm, however there were initial losses in Owasco among the seedlings after transplanting. Inclement weather and issues with the potting soil used reduced numbers. Ten percent of the plants were rogued due to symptoms of stem disease. An affected plant wilted, and displayed a dry tan lesion at the base of the stem, while the roots remained white. There did not appear to be any effect of the preventive treatments on the stem blight incidence. The problem appeared random and did not spread.

Samples were sent to the Long Island Horticultural Research and Extension Center in Riverhead, New York. Fusarium was isolated from lisianthus at both farms. At Hastings Field about 7% of the plants were removed. The crop was less productive than at Folls Flower Farm, evidence that drip irrigation and full sun improve yield. At harvest several nodes remained on the plants, and a second crop is on the way. Both growers will rotate the lisianthus away from the current location to help avoid this soil pathogen. Additional recommendations are to avoid ammonium nitrogen, pH lower than 6.2, and to increase the available calcium in the soil.

The project allowed two members of ASCFG to develop a working relationship that will continue. The two growers traded ideas and plant materials, and already made plans for next spring.

Thea Folls added, “I’m really glad we did the project. I am going to rotate Actinovate, Serenade, and Regalia next year.”

This project was funded by an ASCFG Grower Grant. For more information, see “Research” at www.ascfg.org