Monday, December 29, 2008
Possible Phytotoxicity on Cordyline
These are Cordyline australis 'Southern Splendor' from a finishing operation. The main symptoms are the distorted growth and fusing together of the 'middle-aged' growth . The new growth is unaffected while the oldest growth shows tip burn. The plants were heavily infested with two-spotted spider mites (Tetranychus urticae) with obvious symptoms of yellowing and stippling present. The question from the grower was, "Is the distortion caused by the mite injury or is some other factor involved?"
Mite infestations are not known to cause such extreme symptoms so we needed to look elsewhere. The most likely cause is phytotoxicity caused by an pesticide application. The grower is looking into their rotation of miticides as mites have been a constant problem in this crop. Since they are a finishing operation (meaning they received the plants a few months earlier to grow to the final selling size) the grower may have difficulty tracking down what pesticides were applied before they took possession.
These symptoms have been seen by diagnosticians in other states, but a definitive cause of the problem has yet to be identified.
Two-spotted spider mites and associated injury (yellowing and stippling of older leaves) was observed.