Caused by a bacterium, citrus canker can strip citrus trees of their leaves and cause fruit blemishes, resulting in yield and quality losses. ARS scientists tested windbreaks in Argentina where citrus canker is common. Bacterial sprays are costly and have been only marginally effective. To protect poisettias, researchers also advise growers to use the calcium nitrate form of fertilizer. It apparently makes poinsettias less attractive to the pest than ammonium nitrate, the most common form of nitrogen fertilizer.
Whiteflies destroy plants by feeding on their juices.
ARS scientists found more pests on fertilized poinsettia plants than on unfertilized plants. Researchers found female whiteflies laid more eggs on leaves of plants fertilized with ammonium nitrate, compared with those unfertilized or fertilized with calcium nitrate.