Starting in the late 1950s the emergence of Fusiform rust on South Eastern pine trees including slash pine (Pinus elliottii), loblolly pine, (Pinus taeda), and longleaf pine, (Pinus palustris) led to massive tree mortality within the pine industry.
This obligate parasitic pathogen is notorious for infecting young trees in newer planted areas within the first 1–5 years of growing.
The pine industry was still rather new at the time of this initial outbreak, therefore, many newly planted forests had large-scale mortality because the trees were not yet old enough to be resilient to the disease or harvested.
Florida’s pine industry in particular was booming with an increase in plantation acreage from 291,000 acres (118,000 ha) in 1952 to upwards of 5.59 million acres (2,260,000 ha) in 1990.
Because of the complicated lifecycle of Cronaritum quercuum f. sp.
fusiforme, the fungal causal agent of Fusiform Rust, the management strategies of pruning diseased stems, reducing fertilization, and discarding infected seed were not sufficient enough to prevent million dollar annual loses.

Rust pathogens are difficult to manage because of their complicated reproductive life cycles.
Cronaritum querecuum f. sp.
fusiforme is heteroecious, requiring two different plant hosts for reproduction, and is macrocyclic, meaning it contains all five spore stages typical for rust infections: basidiospores, teliospores, urediniospores, aeciospores, and spermatia.
Oak trees are the secondary host for this pathogen.
The primary inoculum on pine are basidiospores which infect the pine needles in spring between March and May. The basidiospores germinate and grow into the stems of the tree where the fungus can overwinter for 4–6 months in the wood.
In the fall, the spermatia forms and fertilizes the aceiospores in the following spring.
The aceiospores are released from the pine and are the primary inoculum that infect the oak trees in the following growing season.
Aceiospores grow through the oak leaves producing urediniospores on the underside of the oak leaves.
These urediniospores can reproduce clonally, asexually, and can continue to infect oak plants as a secondary inoculum.
Within two weeks of the primary urediniospore inoculation on the oak tree, teliospores are formed which germinate into basidiospores that infect the pine trees and complete the life rust cycle.
Symptoms on the pine include gall formation, stem swelling, cankers, bushiness, and dieback.
The cankers in the stem allow secondary fungal infections or other pests to enter the trees easily.

Understanding the climate conditions that can lead to rust outbreaks is an important component for management strategies, but this was not well understood in the early decades of this epidemic.
More recent information has shown that certain weather patterns such as high humidity, wet pine needles, and temperatures around 15–29 °C (59–84 °F) for approximately 18 days can increase the spread of basiodiospores and therefore increase disease severity.
 
The secondary host, oak, is another economically and ecologically important tree in the south east.
Therefore, eradication of the secondary host is not only not possible but also not effective because basidiospores can travel up to a half mile, easily infecting pine trees that are far away.
Therefore, a combination of management strategies such as reducing fertilization treatments (which can benefit the pathogen), planting more rust-disease resistant trees in plantations and reintroducing fire to reduce the oak trees within the forest may help to reduce disease incidences.
Starting in the late 1950s the emergence of Fusiform rust on South Eastern pine trees including slash pine (Pinus elliottii), loblolly pine, (Pinus taeda), and longleaf pine, (Pinus palustris) led to massive tree mortality within the pine industry. This obligate parasitic pathogen is notorious for infecting young trees in newer planted areas within the first 1–5 years of growing. The pine industry was still rather new at the time of this initial outbreak, therefore, many newly planted forests had large-scale mortality because the trees were not yet old enough to be resilient to the disease or harvested. Florida’s pine industry in particular was booming with an increase in plantation acreage from 291,000 acres (118,000 ha) in 1952 to upwards of 5.59 million acres (2,260,000 ha) in 1990. Because of the complicated lifecycle of Cronaritum quercuum f. sp. fusiforme, the fungal causal agent of Fusiform Rust, the management strategies of pruning diseased stems, reducing fertilization, and discarding infected seed were not sufficient enough to prevent million dollar annual loses.
Rust pathogens are difficult to manage because of their complicated reproductive life cycles. Cronaritum querecuum f. sp. fusiforme is heteroecious, requiring two different plant hosts for reproduction, and is macrocyclic, meaning it contains all five spore stages typical for rust infections: basidiospores, teliospores, urediniospores, aeciospores, and spermatia. Oak trees are the secondary host for this pathogen. The primary inoculum on pine are basidiospores which infect the pine needles in spring between March and May. The basidiospores germinate and grow into the stems of the tree where the fungus can overwinter for 4–6 months in the wood. In the fall, the spermatia forms and fertilizes the aceiospores in the following spring. The aceiospores are released from the pine and are the primary inoculum that infect the oak trees in the following growing season. Aceiospores grow through the oak leaves producing urediniospores on the underside of the oak leaves. These urediniospores can reproduce clonally, asexually, and can continue to infect oak plants as a secondary inoculum. Within two weeks of the primary urediniospore inoculation on the oak tree, teliospores are formed which germinate into basidiospores that infect the pine trees and complete the life rust cycle. Symptoms on the pine include gall formation, stem swelling, cankers, bushiness, and dieback. The cankers in the stem allow secondary fungal infections or other pests to enter the trees easily.
Understanding the climate conditions that can lead to rust outbreaks is an important component for management strategies, but this was not well understood in the early decades of this epidemic. More recent information has shown that certain weather patterns such as high humidity, wet pine needles, and temperatures around 15–29 °C (59–84 °F) for approximately 18 days can increase the spread of basiodiospores and therefore increase disease severity.  
The secondary host, oak, is another economically and ecologically important tree in the south east. Therefore, eradication of the secondary host is not only not possible but also not effective because basidiospores can travel up to a half mile, easily infecting pine trees that are far away. Therefore, a combination of management strategies such as reducing fertilization treatments (which can benefit the pathogen), planting more rust-disease resistant trees in plantations and reintroducing fire to reduce the oak trees within the forest may help to reduce disease incidences.
Pinus elliottii