EFFECT OF SANITATION ON NAVEL ORANGEWORM ABUNDANCE IN AND DAMAGE TO PISTACHIOS

Authors: Burks, Charles - Chuck; HIGBEE, BRADLEY - PARMOUNT FARMING; Brandl, David

Submitted to: California Pistachio Commission Production Research Report
Publication Type: Trade Journal
Publication Acceptance Date: 2/3/2006
Publication Date: 2/17/2006
Citation: Burks, C.S., Higbee, B.S., Brandl, D.G. 2006. Effect of sanitation on navel orangeworm abundance in and damage to pistachios. California Pistachio Commission Production Research Report. pp. 83-90.

Interpretive Summary: The navel orangeworm (NOW) is a highly damaging pest of potential quarantine concern. It is a primary insect pest in pistachios, a crop worth $444 million dollars to California producers in 2004, and in almonds, a $2.2 billion crop. Postharvest sanitation of nuts remaining in the tree is a key component of NOW pest management in almonds. Postharvest sanitation in pistachios is even more laborious and expensive than in almonds and, compared to almonds, there are fewer empirical data showing that it results in a reduction in nut damage. In pistachios, 2% NOW damage is often used as a threshold above which producers receive lower prices. This report describes research showing that pistachios receiving rigorous sanitation had significantly more than 2% NOW damage whereas those receiving minimal sanitation had significantly less than 2% damage, indicating that sanitation was cost-effective. These results provide demonstrate that sanitation for NOW pest management can be effective for reduction of economic loss from this pest in pistachios. Moreover, if rigorous sanitation is more widely adopted it could reduce regional NOW abundance, thereby also benefiting other commodities in the area.

Technical Abstract: In fall 2004 and winter 2005, rigorous or minimal sanitation was applied to pistachio in three paired plots each of 160 acres each. Rigorous sanitation included mechanically shaking after harvest for removal of mummy nuts, blowing fallen pistachios were blown off of the berms, subsequent manual raking of the berms, and disking the alley. In minimal sanitation plots only disking was performed as part of the weed control program. Data collected included the number of mummy nuts remaining after sanitation, weekly counts of NOW eggs on oviposition traps and males in pheromone traps, and fall 2005 harvest samples of ca. 4,000 pistachios were taken from each 2.5 acres within each plot. Damage was expressed as a proportion of infested nuts to split nuts. Rigorous sanitation resulted in a 10-fold reduction of the number of mummies in trees, and a 1,000-fold reduction in the number of mummy nuts on the ground. There was no significant difference between the counts of moths in pheromone traps in the plots with rigorous and minimal sanitation, perhaps because of trap saturation. In the first flight there were significantly more eggs on traps in the blocks with rigorous sanitation than on traps in blocks with minimal sanitation, perhaps because the traps were outcompeted by mummy nuts in the minimal sanitation ploys. Over all three blocks, the plots receiving minimal sanitation has significantly more than 2% NOW damage whereas those receiving rigorous sanitation had significantly less than 2% damage. There was significantly less damage in the rigorous sanitation plot than in the minimal sanitation block in two of the three blocks.