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Thursday, July 14, 2011

What's Happening In The Orchard In July: Limb Damage and Wormy Peaches and Nectarines

Fruit Tree Limb Split Due to Heavy Fruit Load
Limb Damage Due To A Heavy Crop Load.  Too much fruit on a single limb and the weight can cause the limb to separate from the trunk.  We get it at the orchard if we do not thin the fruit enough on the limb or if the limb has a poor attachment to the trunk.  Make sure that limbs which support fruit are attached to the trunk at about a 45 degree angle.  Peaches should be thinned so that the fruit is about 4 to 6 inches apart along the limb.  Summer pruning, talked about here on this blog, will help to keep fruit loads more manageable and cause less damage to the tree.  During summer pruning, usually around April and May, excessively long branches on peaches and nectarines are pruned back so they are no longer than about 18 inches.  This helps to distribute the crop load for the next year which is born on the wood which is produced this year.
Flagging in new growth at the top of a peach tree

Wormy Peaches, Nectarines And Even Almonds. Peach twig borer in the adult stage is a brown month about 1/2 inch long.  After eggs are laid by the adult moths, worms or larva enter soft fruit usually near the stem end.  When they enter near the stem end they leave behind some brown excrement that looks a little bit like wet, dark brown would grindings. 

CloseUp Of DieBack Of A Young Peach Stem Due
To Peach Twig Borer
But earlier in the season when there is no fruit they attack something else that is soft and tender - - newly growing shoots.  They bore into the soft ends of the shoot where they tunnel and cause the newly growing tip to die back as you see in the picture.  Later in the season when there is soft fruit they attack the fruit instead.

It is important to get these insects under control very early in the season.  There can be several generations each growing season and their numbers are not additive but multiply at very high rates so their numbers increase rapidly.  

Peach Twig Borer Larva in Almond Husk
These little guys will also attack almonds.  They get into the husk where it is essentially just like the fruit of a peach.  They can get inside where the nut is located and cause damage there as well.

We use pheromone traps to begin to identifying when they are flying and add a very high density so that we get some mating disruption.  Then we usually use either sprays of Bt or spinosad.

For more information see the University of California IPM online web site at


  1. My garden last year had a severe problem with nematodes destroying the roots so I decided not to plant any tomatoes this year. I recently pulled out some zucchini plants that weren't doing well and found the roots had the same damage I suspect was from nematodes.

    That was a long windup but the question is can nematodes overwinter and affect zucchini plants?

  2. You will continue to have problems with nematodes. They are nearly impossible to eliminate. I have a posting on this blog on nematodes and some control measures you can use to help reduce nematode populations. These alternative measures include using resistant varieties with the designation "N" for nematode resistance (may also accompany "VF"), soil solarization (you can also search for that here on this post) and getting them healthy and trying to grow them "ahead" of the damage and reduced production.