This development of an orchard is an expensive, time consuming process that needs pest management long after the orchard is established. One important disease that occurs in seed orchards is cone rust which is caused by the fungus Cronartium strobilinum . Like that of fusiform rust, this pathogen has five spore stages which occurs on two host. Instead of infecting needles, the basidiospores infect the emerging cone flowers. Here is an example of a cone with the orange-colored aeciospores.
Infection occurs in early spring when female flowers are being produced.
The first indication that rust has infected a cone is that it swells to 2-3 times its normal size. Another example of a infected cone showing the increased size with respect to a normal cone. Both the large cones and aeciospore-covered cones can be observed from the ground during the year. Here it is possible to observe three cones that are infected with the disease. The infected cones do not produce seed and thus, large infestations will decrease the amount of seed collected.