Margaret Tuttle McGrath
Associate Professor, Department of Plant Pathology,
Long Island Horticultural Research and Extension Center, Cornell University
3059 Sound Avenue, Riverhead, NY 11901

Messenger® (EPA Reg. No. 69834-2) is a biochemical pesticide from Eden Bioscience for plant disease management, insect suppression, and plant growth enhancement. It is now labeled throughout the United States, including New York. Messenger can be used on a broad spectrum of crops, including vegetables, grown in field, greenhouse, shadehouse, and nursery production. It is labeled for use on the following vegetables: asparagus, artichoke, sweet corn, cucurbits, tomato, pepper, eggplant, leafy and cole crops, beans and other legumes, beets and other root crops, potato, onion, garlic, and scallion. Messenger is virtually non-toxic and degrades rapidly leaving no detectable residue. This product is promoted as a foundation for IPM programs because of its ability to increase plant health without adversely affecting beneficial organisms.

Messenger contains a new active ingredient, HarpinEa. It is based on naturally occurring proteins called “harpins” that are produced by bacteria and other microbes. More specifically, HarpinEa is chemically identical to the harpin produced naturally by Erwinia amylovora, the plant pathogenic bacterium that causes fire blight. Zhongmin Wei discovered the harpin protein while working in the laboratory of Steven V. Beer in the Department of Plant Pathology at Cornell University. Pathogenic bacteria need harpins to infect their host plants. In other plants, harpins bind to plant receptors which leads to stimulation of the plant’s own pest suppression systems.

HarpinEa does not have any direct pesticidal effect on insects or pathogens. Messenger reportedly reduces damage caused by some insects through making plant material more difficult for insects to digest. Diseases listed on the label include bacterial spot and Phytophthora root rot of tomato and pepper; bacterial speck, root-knot nematode, and Fusarium wilt of tomato; and cucumber mosaic virus affecting cucurbits and eggplant. In an experiment conducted with pepper in California, Messenger applied 6 times at 3.53 oz/A was as effective as maneb (Manex 4F at 2 qt/A) for bacterial spot (53% and 60% control, respectively) and for powdery mildew (70% and 86% control). In another experiment with tomato, Messenger applied 6 times at 4.5 oz/A was at least as effective as copper (Kocide 101 at 2 lb/A) for bacterial speck (control of symptoms on leaves was 69.3% and 24.8% on 6/19, 60.4% and 43.4% on 8/14). Messenger applied 6 times to tomato at 3.9 g/A was as effective as maneb (Manex 4F at 2 qt/A) for bacterial speck (53% and 60% control on leaves, respectively and 53% and 60% control on fruit) in another experiment.

While evaluating efficacy of Messenger for various diseases and insect pests, it was noted that this product also enhances plant growth. Effect of Messenger on plant growth reportedly has been more consistent than its effect on pests. Both nutrient uptake and photosynthesis are stimulated. This has resulted in earlier yield and increased yield. For example, in an experiment conducted with several processing tomato varieties at five farms in California, Messenger applied at 2.29 oz/A on a 14-day interval from the 3-leaf stage within the normal grower fungicide program of 0 – 2 applications of chlorothalonil (Bravo at 1.5 lb/A) resulted in significantly more red marketable tomatoes (average of 90 vs. 80 lb) and less loss to fruit rot (3.1 vs 3.9 lb). In another experiment, Messenger applied 3 times at 2.29 oz/A resulted in 55% more fruit present 6 weeks before harvest compared to grower standard of chlorothalonil (34.8 vs. 22.4 fruit greater than 1-inch per plant) and 18.2% more red marketable fruit by weight at harvest (118.6 vs. 100.3 lb). Research is underway in the northeast this summer to determine whether these growth effects observed in Florida and California also will occur under our climatic conditions. Thus only trial use can be recommended in the northeast until this work is done. A Twilight meeting will be held at the Long Island Horticultural Research and Extension Center this summer to share results of research being conducted there with tomatoes and peppers.

Growers planning to try Messenger need to be aware that the current formulation cannot be used with chlorinated water. Either use well water or other non-chlorinated water, or obtain WTA, which inactivates chlorine, from Eden Bioscience. Also, note that the product does not keep after the package is opened, therefore it is marketed in single-use packages. Current guidelines are to apply Messenger as a foliar spray at approximately 14-day intervals beginning at least 5 days before transplanting. The label includes guidelines for applying Messenger as a drench for greenhouses set-up to apply pesticides this way (section 12); however, material applied to foliage will have the greatest impact. A maximum annual use rate is not specified on the Messenger labeling.