MANILA, Philippines - The ornamental plant farmers going into large scale production usually result in invasion of non-traditional pests. One of the more common pests resulting from over fertilizing with high nitrogen fertilizers is bacterial infection.
Sansevieria growers of Malaysia grew their crop for two years without incident. The third year shows fungal infections which were easily controlled by fungicides but the plants eventually succumb to bacterial rot that resulted in total destruction of the farm.
The Great Bacterial Infection of Anthuriums of Hawaii during the 70’s is suspected to be of this nature. Currently, we have the melting Aglaonema syndrome happening allover Southeast Asia as growers push for more Aglaonema plants with high Nitrogen feed. Tulip Ginger (Curcuma alismatifolia) growers and exporters in Thailand stopped exports because of Xanthomonas infections a decade ago.
Orchid growers are not exempted from this. As the orchid farms push to compete, higher nitrogen rates are used to increase the rate of growth of the plants beyond their natural growth rate, more incidence of bacterial rot shows up.
High Nitrogen and Bacterial Infection
The plant has several mechanisms to cope up with bacterial infection but production system providing high nitrogen usually encourages the farmers to keep on applying the same levels of Nitrogen without the correspondingly essential secondary nutrients: Calcium and Magnesium.
Fertilizer companies always assume that the plants will get their secondary nutrients from ground water or from river sources. Normally this is sufficient if plant is growing at natural rate. With the use of high nitrogen, it is possible to increase the rate of cell proliferation and growth by ten folds or more, thereby increasing the need for more secondary and trace elements.
As plants get faster growths and less Calcium, the system will be wanting in the most important nutrient for cellwall integrity and the middle lamella (the chemical cementing the cells together) will thin out. As the middle lamella weakens due to lack of Calcium pectate, the cells are vulnerable to infections.
Production System Defect
Bacterial diseases are treated as ‘Production Systems Defect’ in the Netherlands. That means it is preventable. Canopy over the plant, wind movement may be provided and proper levels of nutrients (including Calcium and Silicon) may be provided when growth are forced on the plants.
In Asia, bacterial infections are treated as regular disease and antibiotics (usually veterenary grade Tetracyclines and Streptomycins) are recommended by inexperienced agriculturists. The bacterial applications seldom work but a curious phenomenon happens: After several antibiotic sprays, the chlorophyll of the new leaves starts to disintegrate. The young leaves eventually end up white or pink. The symptom is similar to glyphosate and 2,4-D (both herbicides) toxicity of plants.
This toxic characteristic is exploited by the Sansevieria traders in Indonesia. They treat Sansevierias with multiple applications of either antibiotics or low dose herbicides and pass the plant off as expensive variegata-form. Unsuspecting customer will find out later that they paid high price for ordinary materials as they nurse the plants back to health.
Antibiotics are not recommended for bacterial infections. It is impossible for the chemicals to find and kill all the bacterial cells through spraying. Plant and bacterial cells are very similar. Chemicals that will affect the bacteria will also affect the plant cells. Nothing will replace good aeration, good sanitation and God Speed Gardening (i.e. no high nitro feed).