Effect of nitrogen source on growth and susceptibility of Anthurium hybrids to Xanthomonas campestris pv. dieffenbachiae

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A. R. Chase and R. T. Poole*

University of Florida, IFAS
Central Florida Research and Education Center - Apopka
CFREC-Apopka Research Report, RH-90-20

One of the most damaging diseases of Anthuriums worldwide is Xanthomonas blight caused by X campestris pv. dieffenbachiae. This disease has caused losses in the millions in the Hawaiian cut flower industry and affects production of all types of anthuriums including those grown as potted plants. This disease is characterized by marginal infections which are yellow initially, later turning brown and spreading into the centers of the leaves. Flowers may be affected as well. The bacterium which causes the disease is easily splashed with overhead irrigation or rainfall and is very difficult to control under any growing system which includes overhead irrigation. Use of bactericides has proven a poor control method since many cultivars of the anthurium are sensitive to copper and streptomycin sulfate compounds. Research during the past few years has shown that while fertilizer level affects susceptibility of anthurium to this pathogen it also affects flowering and growth of the plant. The best fertilizer level for growth of the plant, unfortunately, results in the highest susceptibility to the pathogen (1, 2). Additional research on the source of nitrogen was suggested to determine its potential for disease control. Two anthurium hybrids, 'Princess' and 'Southern Blush', were tested with nitrate and ammonium sources of nitrogen for growth response and susceptibility to X campestris pv. dieffenbachiae.

Methods

Anthurium plants originally from tissue culture were obtained from commercial growers. Plants were established in a mixture of Vergro and pine bark (1:1 by volume) and utilized in tests when they reached about 6 inches tall. Fertilizer was applied once a week in a liquid form and consisted of 50 ppm nitrogen (from different sources), 25 ppm potassium (from KC1), and 7 ppm phosphorous (from H₃P0₄). Nitrogen treatments were as follows: 100% ammonium [(NH₄)₂SO₄], 50 % ammonium and 50% nitrate (NH₄N0₃), and 100% nitrate [KN0₃, NaNO₃, and Ca(NO₃)₂]. Plant ratings included number of leaves, height, and top quality at test completion. Top quality was rated as follows:l (dead), 2 (poor, unsalable), 3 (good, salable), 4 (very good, salable), and 5 (excellent, salable). Plants were inoculated using standard methods with a suspension of the pathogen and plants were placed under intermittent mist for about 3 weeks to promote disease development. Disease severity was rated as the percentage of the foliage with symptoms of blight and/or the number of leaves with symptoms of blight. The first test was conducted with 'Princess' and started on 9 November 1989 with disease ratings on 19 March 1990. The second test included 'Southern Blush' and 'Princess' and started on 9 April with disease ratings on 13 July 1990.

Results

Nitrate nitrogen resulted in a slight reduction of height for 'Princess' in test 1 but gave a slight increase in height in test 2 with height of 'Southern Blush' unaffected by nitrogen source (Tables 1, 2 and 3). Number of leaves was not affected for either anthurium hybrid in these tests although 100% ammonium resulted in some leaf damage due to chlorosis of lower leaves in the summer test on 'Princess' (Table 2). Top quality was only affected in test 2 for the 'Princess' and was slightly better for plants receiving the 100% nitrate source of nitrogen (Table 2). Overall, plant growth was not consistently or significantly affected by these fertilizer treatments.

The disease response was similar in that fertilizer source did not consistently affect severity of Xanthomonas blight. In the first test on 'Princess' disease severity was slightly higher for plants receiving the 100% nitrate fertilizer compared to the 50-50 mixture and the 100% ammonium source (Table 1).

Conclusions

'Princess' and 'Southern Blush' plants grew equally well when fertilized with 100% ammonium, 50% ammonium and 50% nitrate, or 100% nitrate nitrogen. Although disease severity was affected by fertilizer treatment in one of three tests, the response was slight and is apparently not reliable. Unfortunately, anthurium producers cannot affect severity of Xanthomonas blight by altering the fertilizer program with respect to either rate or source of nitrogen.

*Professor of Plant Pathology and Environmental Horticulture, respectively. Central Florida Research and Education Center, 2807 Binion Rd., Apopka, FL 32703-8504.

References

1. Chase, A. R. 1989. Effect of fertilizer rate on growth of Anthurium andraeanum and susceptibility to Xanthomonas campestris pv. dieffenbachiae. pp. 4849 In Proc. Second Anthurium Blight Conference. Hawaii Inst. Trop. Agric. and Hum. Resour. 02-22-89.

2. Chase, A. R., and R. T. Poole. 1986. Effects of nutrition on growth and susceptibility of Anthurium scherzeranum to Xanthomonas leaf spot. Nurseryman's Digest 20(6)-58-59.

Table 1.(Test 1) Effect of nitrogen source on growth of Anthurium 'Princess' and severity of Xanthomonas blight caused by Xanthomonos campestris pv. dieffenbachiae.

^aSignificance of the F test was denoted as ns (not significant) or ** (significant at the 1% level).

Table 2.(Test 2). Effect of nitrogen source on growth of Anthurium 'Princess' and severity of Xanthomonas blight caused by Xanthomonos camnestris pv. dieffenbachiae Treatment.

^aSignificance of the F test was denoted as ns (not significant) or significant at the 1% (**) or 5% (*) level.

Table 3. Effect of nitrogen source on growth of Anthurium 'Southern Blush' and severity of Xanthomonas blight caused by Xanthomonas campestris pv. dieffenbachiae.

^aSignificance of the F test was denoted as ns (not significant) or significant at the 1% (**) or 5% (*) level.