Abstract
Stem injections with phosphite liquid protect B. grandis and E. marginata from P. cinnamomi for at least four years . However, stem injection of phosphite is labour intensive and requires training, specialised equipment, and the mixing of chemicals. The recent development of soluble phosphite implants which can be quickly inserted into stems, overcomes the need for training and the use of specialised equipment. Systemic nutrient implants and injections have been effectively used to correct nutrient deficiencies in ornamental and horticultural plants and can help increase tree vigour to pests and pathogen attack. However, soluble implants of phosphite and nutrients have never been trialled for the control of Phytophthora. This study aimed to determine if liquid phosphite, soluble implants of phosphite alone, or combinations of macro and micro nutrients within implants inserted into the trunks of the trees could control lesion development caused by P. cinnamomi. In B. grandis and E. marginata, phosphite liquid and soluble phosphite implants significantly reduced lesion length compared to the control and application of nutrient implants. In B. grandis and E. marginata, nutrient implants reduced significantly the average lesion length compared to the control. Results show that both phosphite liquid and implants are effective at controlling lesion extension in B. grandis and E. marginata, caused by P. cinnamomi. Stem treatment with soluble phosphite implants will facilitate the rapid treatment of trees, and control of P. cinnamomi, in diseased areas. In addition, the uptake is passive, there is likely less damage to internal stem tissues, and less risk from phytotoxicity due to slow release of the phosphite compared to the liquid treatments.