Cooperative Extension Fresno County
University of California
Cooperative Extension Fresno County

April

Fireblight

Q.  The flowers, new shoots, leaves and twigs (sometimes fruit) on my apple, evergreen pear, hawthorn, loquat, cottoneaster, pear, pyracantha or toyon have suddenly wilted, then turned brown and black and died back.  They look like they've been scorched.  What is the problem?

Fireblight
A.  Fireblight is a bacteria that infects the new spring growth of members of the rose family that produce pomes (apple-like fruit).  During warm, wet weather the bacteria are found in brown droplets oozing from cankers and are spread by pollinators and splashing water to the flowers and then to twigs.  Verify the presence of fireblight by peeling back newly infected bark-the wood will have a reddish-brown discoloration.

Prune diseased wood back at least 6 inches into healty tissue.  Entire branches may need to be removed, possibly changing the balance of the plant.  Small, heavily infected plants are best destroyed.  Do not put prunings into a compost pile or keep in the yard.  Burn them or dipose of them in the trash.

Sterilization of the pruning instruments between each cut with a 10% bleach solution has long been recommended to prevent the spread of the bacteria.  Newer studies cast doubt on the efficacy of this practice, but it sure can't hurt.  A weak (about 1/2%) Bordeaux mixture or other copper fungicide applied several times as buds open can reduce infection.  Fungicide labels will provide timing and application instructions. 

Pest Note:  Fireblight 

 

Peach Leaf Curl

Q.  The new leaves on my peach/nectarine tree are thick, puckered and curled up.  They are pale green at first and then turn bright red or purple and fall off prematurely.  Why?  And last year some of the nectarines had raised, rough areas on the skin.  What causes that?

Peach leaf curl
A.  Peach leaf curl is caused by a fungus that is carried by wind and rain.  The spores lodge in cracks in the bark and in the bud scales.  The premature leaf drop should be followed by a second, healthy growth of foliage and minor infestations rarely kill the tree.

Remove affected leaves as soon as you see them, before spores fully develop, and dispose of them in the trash.  Keep the tree healthy and promote replacement foliage growth with regular deep irrigation and fertilization.  Copper fungicides can be applied twice yearly-just after leaf drop in the fall (usually November) and at bud swell in spring (usually mid-February).  Drench the branches, trunk and the soil under the tree to kill off as many fungal spores as possible.

The raised, rough spots on necatines are also caused by the peach leaf curl fungus. 

Pest Note:  Peach Leaf Curl  

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