Applying Apogee and Actigard to young apple trees
Apogee and Actigard applied together can help suppress fire blight while not seriously delaying the trees filling their canopy space.
Apple growers plant new trees with the goal of growing them as fast as possible to fill the space. After filling the space, they want the trees to change to a fruiting mode to start producing a crop immediately. Trees are pushed to grow rapidly, but pushing trees to fill space puts them at a greater risk infection from fire blight. Apogee from BASF and Kudos from Fine Americas are great suppressors of fire blight, however they are Prohexidione-calcium products and anti-gibberillin plant growth regulators (PGRs) that reduce shoot growth, so they are not used on new trees due to their effective reduction in shoot growth, thus delaying trees to fill the space. Actigard and Apogee combined, however, may provide an answer to protect young apple trees and still fill the space.
Actigard is known to suppress fire blight by its systemic acquired resistance stimulus on the apple plant. It is known to suppress fire blight effectively for about 10 days, thus repeat sprays should be applied every 10 days. Apogee is also known to suppress fire blight by its anti-gibberellin impact on the plant. Apogee thickens cell walls and reduces shoot growth, thus providing a fairly effective physical barrier to fire blight growth. These materials applied together can provide a synergistic suppression of fire blight.
On young trees, using low rates of Apogee allows the early season growth suppression and fire blight protection. The low rate effect wears off during early summer. Young trees will tend to start growing vigorously again during the summer months (July and August) when fire blight risk is lower. Adding Actigard to the Apogee will provide additional fire blight protection to the low Apogee rates during the spring high risk months.
Recent research by George Sundin of Michigan State University conducted over the past few years measured the effectiveness of low rate combinations of Apogee and Actigard on suppression of fire blight on apple trees. The results were very promising. Two treatments of the Apogee and Actigard combination provided excellent suppression of fire blight. Treatments of 2 ounces of Apogee and 1 ounce of Actigard per acre applied starting at king bloom petal fall and then again 10 days later suppressed fire blight lesion development. In severe fire blight years, a third or forth application every 10 days may be necessary. The Apogee and Actigard combinations should be applied every 10 days.
Apply Apogee when the vegetative shoot growth is 1 to 3 inches. This is about a seven-day window commencing at the pink stage to the king bloom petal fall stage. Most years, all varieties can be treated at this time. Apply the second application two weeks later and the third application two weeks after the second. Sometimes a fourth application is needed, but that is optional based on crop load and tree vigor.
The loss of an apple crop may require a fourth and perhaps a fifth application of Apogee. Excessive rainfall and light crops will promote vegetative growth, therefore more applications and material will be needed.
In summary, using Apogee and Actigard together in low rate combinations during the early development of young trees can provide an additional tool to suppress fire blight and not stifle the shoot growth to the point of seriously delaying the trees filling their canopy space.