Harvest load gradesheet data for pistachios 2007-2017

The navel orangeworm, Amyelois transitella, is the
primary pest of pistachios in California. The first A.
transitellaoutbreak of the twenty-first century occurred in 2007 and a
total of five outbreaks occurred between 2007-2017 (total insect damage
> 1%). This study used processor information to identify the nut
factors associated with the outbreaks. Processor grade sheets were used to
explore the relationship between the variables time of harvest, percent
nut split, percent nut dark staining, percent nut shell damage and percent
adhering hull for Low Damage (82,537 loads) and High Damage years, (92,307
loads). Total insect damage (±SD) for the Low Damage years averaged
0.005±0.01 and in High Damage years was three times higher, 0.015±0.02. In
Low Damage years the strongest correlation was between total insect damage
and two variables, percent adhering hull and dark stain (0.25, 0.23) while
in High Damage years the correlation between total insect damage and
percent dark stain was the highest (0.32) followed by percent adhering
hull (0.19). The linkage of these nut factors to insect damage suggests
that outbreak prevention depends on early identification of premature hull
split/breakdown in addition to the traditional emphasis on treating the
standing population of A. transitella.