Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: October 3, 2009
Publication Date: November 13, 2009
Citation: Kuenen, L.P., Siegel, J.P. 2009. Spring emergence pattern of navel orangeworm from pistachio and almond mummies. International Conference on Methyl Bromide Alternatives and Emissions Reductions, November 10-13, 2009, San Diego, California. 90: 1-4. Interpretive Summary: The navel orangeworm (NOW)is a major insect pest of pistachios and almonds in California. Under field conditions, spring-time NOW emergence showed only a single peak from pistachios whereas NOW emergence from almonds showed at least three peaks. The single emergence peak from pistachios was confirmed in laboratory studies; large sample size plus degree-day modeling showed that emergence would have lasted until mid-July, a full four months after emergence began. This indicates that late-emerging NOW adults can infest new crop nuts, supporting the perspective that orchard sanitation standards are not stringent enough. This direct movement into new crop nuts along with NOW’s known rapid development on new nuts leads to early overlapping NOW generations that lasts throughout the growing season.
Technical Abstract: The navel orangeworm, Amyelois transitella, is the primary insect pest of pistachios and almonds in California. Four years of research (2002-2006) were conducted in Madera and Kern counties to elucidate the pattern of emergence of the overwintering navel orangeworm population. Springtime emergence from unharvested (mummy) nuts was protracted (as long as 600 degree-days Celsius from January 1 of each year) and in 2004 and 2006 extended as late as mid-July. The sex ratio of adults emerging from pistachio mummies was significantly skewed (P < 0.001) with a ratio 57:43 male:female. Emergence from mummies held outdoors (variable temperature) began in early March and continued through early June. The adult emergence pattern from pistachios contained a single emergence peak while emergence from almonds occurred in multiple peaks. These same patterns occurred when mummies were held at constant temperature indoors, and the emergence peak from pistachios occurred sooner. The impact of these findings on understanding NOW population dynamics and current control recommendations is discussed.