Commodities: Fruits

The Georgia Peach

2008 Tropical Storm Damage to South Georgia Peach Orchards

Kathryn Taylor, Pomologist

Dan Horton, Fruit Entomologist

Phil Brannen, Fruit Pathologist

University of Georgia

Late August 2008, Tropical Storm Faye buffeted South Georgia peach production areas with tropical storm-force winds while flooding fields with more than 10 inches of rain.  Peach trees of all ages were pushed over or uprooted by these winds.  Lessons can be learned from a similar storm, Hurricane Francis (2004) that fatally traumatized, many apparently normal, trees in 3-year-old and younger orchards.  The affected trees leafed out the spring of 2005, giving the allusion of having successfully survived storm injury.  However, by late spring significant numbers of storm-injured peach trees were showing signs of major trauma and decline expressed by tree collapse and death. 

We learned several things during the following spring.  First, in many cases the hurricane winds wallowed-out basins surrounding the young trees, trapping excess rain, further exacerbating the already serious stresses associated with prolonged exposure to waterlogged, deoxygenated soils.  This time around we suggest that every tree in an affected area should be assessed for this damage, and the soil replaced tightly around the truck, as soon as possible after the event to avoid having the roots standing in water. Second, numerous other storm-injured trees succumbed to opportunistic stresses such as storm-facilitated belowground attacks by peachtree borer and fungal pathogens that take advantage of weakened or flood stressed root systems.

Peachtree borer attacks initiated below ground are highly atypical. While peachtree borers will often attack major roots that extend up to the soil line, attacks to below ground regions of the trunk are uncommon. These atypical below ground attacks appear to be facilitated by wind creating substantial gaps in the normally tight alignment of soil and the lower trunk. Barrier insecticides to the lower trunk normally provide excellent control of peach tree borer. However, storm-induced gaps between the trunk and the ground line that develop after late summer borer sprays are not protected. Peachtree borers that lay eggs in these storm-induce gaps are effectively sneaking below the normally effective barrier protection provided by handgun applied chlorpyrifos. Follow-up post storm treatments are very much in-order for any blocks that have obvious storm-induced gaps between the trunk and the soil. For these refresher treatments, mix 3 pints of chlorpyrifos 4E per 100 gallons of water and apply with a hand gun to the lower trunk. Put out enough spray to thoroughly wet the wind-induced gap below the soil line. Peachtree borer moths are also able to lay eggs adjacent to storm exposed or broken peach roots, so it is important to also spray exposed roots.

Blown over trees, especially young trees, that are righted and braced with forked limbs etc., are very readily attacked by lesser peachtree borers. Wind-related abrasion, where the wind thrown trees rubbed against their braces, were very heavily attacked by lesser peachtree borer after Hurricane Francis. Apply a soaking application of chlorpyrifos to any wind-abraded areas when treating for storm-induce gaps in protection at the soil line.

Likewise, once trees are established, substantial destruction by root pathogens, such as Phytophthora root rot, is considered to be rare.  However, storm injured young trees incurred tremendous losses from this root-rotting fungus. Applying ProPhyt® immediately after trees have been damaged may be helpful in combating Phytophthora. The recommended rate for peaches is 2 pints per acre in 100 gallons. ProPhyt® can be sprayed at 60 day intervals with a maximum application of 4 times a year.

 

Tropical winds cause trees to twist and roots to break. These breaks cause wounds in the trees.

Dead and dying peach trees.  Peach trees were whipped around by high winds following hurricanes and tropical storms in the fall of 2004.  Roots were torn, allowing for infection by Phytophthora species (possibly other root rot species as well).  Decline symptoms were observed in the spring and summer of 2005.

Young trees blown by heavy winds.  This tree is representative of many young trees which were planted in either 2003 or 2004.  Since leaves were still on the trees when hurricanes came through in the fall of 2004, they were often blown over.  Roots were ripped as the trees were blown about, and this allowed for infection by Phytophthora species, resulting in root and crown rot. In some cases, losses were greater than 50%.

Belowground symptoms of Phytophthora root and crown rot.  Roots rot as a result of fungal infection, resulting in brown, dead tissue (left).  The crown symptoms are exemplified by a canker which generally has a dark red to orange-brown border where it meets healthy green tissue (right).  Cankers generally do not extend above the crown, but they can sometimes extend up the trunk.  

 

Questions or comments?
Contact:

Rebekah Auman

ralong@uga.edu