Monday, July 18, 2011

Almond Crop Is Behind, but NOW Development on Time

Walt Bentley, left,  offers some tips at our almond  field day.
Editor’s note: This week, we are featuring a guest blog by UC IPM entomologist Walt Bentley, whose specialty includes managing pests in almonds.

As we all know hullsplit of Nonpareil almonds, the most susceptible cultivar to navel orangeworm (NOW), is almost 2 weeks behind schedule in the central San Joaquin Valley.

  Interestingly, the development of the second generation of NOW is not behind schedule with eggs being laid during the first week of July (see chart below).  This presents an interesting situation.  I believe many of these eggs will result in suicidal emerging larvae, since they will not be able to infest the nutmeat until hullsplit occurs.

NOW's 2nd generation emerging.
 This doesn’t mean we are home free concerning NOW infestation, however.  It points to the importance of timing sprays to the development of the susceptible stage of the nut (initiation to 5 percent hullsplit). Such timing will optimize the effects of any insecticide applied with the residual remaining through the complete second generation egg laying.  I believe a good portion of the early second generation eggs will hatch and be unable to infest the nut.  The remainder of the generation, that can reach the nutmeat, will be shorter in time duration than normal.  If sprays are timed correctly, excellent chemical control should be achieved. 

Hullsplit is behind schedule in the Valley.
The same scenario that could optimize control of NOW in Nonpareils may result in making later splitting varieties such as Carmel, Sonora and Price more susceptible.  This is a scenario that we see from time to time.  Here the third generation eggs may be timed to Carmel hullspit, resulting a greater potential for infestation.  So, try to focus on early harvest of any late soft shell variety. It may still be a good idea to monitor egg traps to see how NOW egg laying coincides with the hullsplit of these later soft shell varieties.  This can give you an idea if additional chemical control may be needed.
Walt Bentley is a long-time entomologist with the University of California Statewide Integrated Pest Management program at the Kearney Ag Center in Parlier.

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