Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 2008
Publication Date: September 15, 2008
Citation: Burks, C.S., Higbee, B.S., Brandl, D.G., Mackey, B.E. 2008. Sampling and pheromone trapping for comparison of abundance of Amyelois transitella between almonds and pistachios. Entomologia Experimentalis et Applicata. 129: 66-76. Interpretive Summary: The navel orangeworm is a key pest of California almonds and pistachios crops with a collective value of >$2 billion per year (unprocessed). We used data from sanitation samples and pheromone trapping data to compare estimates of navel orangeworm density in these two crops over 2 years. There were consistently far more pistachios than almonds left on the ground in mid-winter, and there were consistently more males captured in pistachios than in almonds in mid-summer. The estimates of density of navel orangeworm (as opposed to mummy nuts) were more similar between the two crops and variable between the two years. We conclude that the overwintering generation of navel orangeworm is able to reproduce more successfully in pistachios than in almonds under current commercial practice, making pistachios a more favorable habitat. These data indicate that an area-wide program that successfully reduces abundance of navel orangeworm in both almonds and pistachios, often planted in close proximity, could reduce financial risk from the pest in both crops.
Technical Abstract: The navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), is the primary insect pest of almonds, Prunis amygdalus Batsch, and pistachios, Pistacia vera L., in California, USA. Abundance of A. transitella was compared between these crops by examining total and infested mummy nuts collected in trees and on the ground between January and March in 2003 and 2004; and the number of males captured in sticky traps baited with virgin females as a pheromone source during the subsequent growing seasons. There was an eight- to nine-fold greater density of total mummies (potential hosts) in pistachios compared to almonds. The proportion of mummies infested was not significantly different between the crops in 2003, but significantly more almond than pistachio mummies were infested in 2004. In 2003 the average density of infested mummies per hectare was greater in pistachios than in almonds, but in 2004 the converse was true. Examination of meteorological data did not suggest an explanation for greater numbers of live A. transitella per infested mummy in almonds in 2004. The number of males captured in pistachios was consistently greater than the number captured in almonds, particularly during the second flight in June and July. The number of males captured in sticky traps in the summer was more strongly associated with the total mummy density in the sanitation survey the previous winter than with the density of infested mummies. We conclude that the overall density of mummy nuts serving as potential oviposition sites prior to the next years crop has a greater impact on the abundance of A. transitella during the growing season and subsequent harvest than does the density of infested mummies.