canker syndrome." Second, cankers may de- 

 velop in twigs, small branches, or around prun- 

 ing cuts but remain localized. This type of 

 canker generally results in only minor damage 

 to the tree. Third, trees may leaf out normally, 

 followed by sudden wilting and total tree death. 

 In cases like this the tree usually is severely 

 damaged by cold temperatures and the trunk 

 and lower scaffold Umbs quickly are colonized by 

 Cytospora. Again, tree health and environmen- 

 tal factors play a major role in the severity of 

 Cytospora. 



Since both species of Cytospora reqmre a 

 wound or natural opening to infect peach trees, 

 proper priming and pest management practices 

 help prevent serious infections. Pruning in fall 

 or early winter can contribute to Cytospora 

 infections because pruning cuts made at these 

 times do not heal as quickly as those made in the 

 spring. 



For injured or weak trees, there are no 

 chemical control measures for Cytospora that 

 have proven completely successful, partly be- 

 cause spores can be released throughout the 

 year. If only a few cankers are present, remov- 

 ing and destroying infected branches below any 

 sign of disease can be helpful. Do not plant new 

 pe ach orchards on poor si tes . Do not prune in the 

 fall or early winter. Additional measures that 

 will help prevent Cytospora canker infections 

 include the following: 



1. fertiUze trees early in the spring to avoid late 

 growth spurts; 



2. avoid mechanical injury to trees; 



3. apply a fungicide spray after pruning, but 

 before a rain; 



4. avoid weak crotch angles; and 



5. whitewash southwest sides of trees and 

 lower limbs (this practice can help prevent 

 injury due to cold temperatures). 



Brown Rot 



As mentioned in "Peach Pest III," brown rot, 

 Monilia fructicola, can infect twigs. When the 

 fungus moves into woody tissues it causes the 

 development of small CEinkers. Cankers, as they 

 grow, can girdle twigs eventually, resulting in 

 withering and death of terminal growth. Gum- 



mosis often accompanies spur blight and canker 

 formation. 



Cankers caused by brown rot may develop as 

 a result of blossom blight or may move down 

 from the finiit pedicel into a twig or larger 

 branch. On twigs or small branches, brown rot 

 cankers normally are eUiptical, well-defined, 

 and brown. During wet weather, gummosis 

 appears, followed or accompanied by tufts of 

 grey spores. Cankers on larger branches caused 

 by rotted fruit appear (similar to those described 

 above, but likely to be much more severe and 

 eventually kill the infected branch). In the year 

 following severe canker development, leaves 

 above the girdling cankers first appear normal 

 then later turn yellow, wilt, and eventually die. 



Phytophthora Root and Crown Rot 



Crown rot does not appear to be a serious 

 problem in Massachusetts peach orchards, but a 

 brief description is given below. 



Waterlogged soil, air temperature, plant 

 nutrient status, species of Phytophthora in- 

 volved, and susceptibility of host tissue all play 

 roles in the occurrence and severity of 

 Phytophthora infections. Most infections occur 

 during the spring, summer and fall months and 

 are spread by infected plants, soil, or water. 

 Infections that occur in crowns or larger roots 

 (especially of yoimg trees) spread rapidly, oft^n 

 killing trees in one or two seasons. Infected trees 

 may appear healthy in the fall, leaf out normally 

 in the spring, but then collapse when warmer 

 temperatures occur. Symptoms of infection 

 vary fi-om withered, bright rust-colored leaves 

 on severely infected trees to decreased overall 

 growth and smaller, yellow leaves on trees that 

 show slower decline. Infected roots or crowns 

 show reddish-brown necrosis of bark and outer 

 wood with a distinct, layered margin; however, 

 after some time roots decay and turn grey-black. 



Avoiding waterlogged soils, proper schedul- 

 ing of irrigation, and proper planting practices 

 help prevent Phytophthora infections from oc- 

 curring and becoming severe. 



Bacterial Canker 



Bacterial canker, caused by either Pseudo- 



Fruit Notes, Winter, 1993 



