Mae Culumber

550 E. Shaw Avenue Ste. 210-B
Fresno, CA  93710
Phone: (559) 241-7526
Fax: (559) 241-7539

Mae 3

Walnuts

Common Damage Characteristics

Nut Damage

 Kernel  Frass  Webbing  Boring Feeding Behavior   Other

  NOW damage

Deep Chewing into kernel.  White, often a lot. Yes, often a lot.   Yes, into kernel.

Larvae feed in groups.

Many per kernel.

 
Shells of heavily infested nuts appear oily. 

  Codling Moth Damage

Deep Chewing into kernel.   Frass at point of entry into the husk.   Very little.  Yes, into husk and kernel. Single larva feeds per kernel.   N/A

Ant Damage

Tunnels chewed into the kernel.  No   No No  Ants feed in groups.  N/A 

  Husk Fly Damage

 

Early season infestations may cause shriveled/
darkened kernel.

Late season infestations do little kernel damage.

No  No  Yes, into the husk. 

Larvae feed in groups.

Many larvae per husk.

 

Husks are blackened and shell is stained black.

Husks cannot be removed cleanly from shell.

 

Sunburn Damage

One side of the nutmeat darkened and shriveled.  N/A  N/A   N/A N/A 

One side of husk darkened and shriveled.

Husks can be removed cleanly from shell.

 

Flowering

Walnuts are monecious, which means that the male and female flowers are on the same tree. Because of this, walnuts are self-pollinating and require no bees. After pollination in the winter, the male flower (catkin) falls off.

Illustration

Pests

Husk Fly (Rhagoletis completa) 

Adult female Husk Fly pierces the husk of the walnut and deposits eggs. After hatching, the maggots feed inside the husk, turning it very soft and  black