NOW Monitor
Navel Orange Worm – the Insect
The following are some salient points about Navel Orange Worm (NOW). This information is not exhaustive about the insect. But it provides the Pest Control Advisor (PCA) and grower with some guidelines about the insect. For more details contact your local farm advisor or PCA. References from where this information was gathered are included at the end of this section.
The NOW Life Cycle:
NOW overwinter mostly as larvae, some as pupae, in mummy nuts.
NOW spends the spring in mummy nuts.
The lower developmental threshold of NOW is 12 C (55 F) *1
The upper developmental threshold of NOW is 34 C (94 F) *1
They emerge as adults in March to May.
Adults emerge late March and April. Peak emergence occurs in April and May. *2
Development time on mummy nuts can be 1.48 times longer than on new crop nuts *2
On Mummy almonds the generation time from adult to adult is 1092 Degree Days (DD) to 1121 DD (Fahrenheit) and 607 DD to 623 DD(Centigrade). * 1 *2
On new crop almonds the generation time from adult to adult is 738 DD to 765 DD (F) and 410 DD to 425 DD (C). *1 * 2
Day degree accumulation from egg hatch to larvae is 99 DD (F) and 55 DD (C). *1
Day degree accumulation to complete the pupal stage is 113 DD (F). *2
Males develop slightly faster than females.
NOW passes through 5 and 6 larval instars during development on new and mummy almonds.
Percent mortality, average development time (days) and average degree days required for development of NOW eggs at 6 constant temperatures *2
| Temperature (C) |
Percent Mortality |
No. Surviving |
Avg. time (days) +/- SD |
Avg. Degree-Days |
| 36.7 C (98 F) | 53 | 25 | 3.4 +/- 0.15 | 78 |
| 34.4 C (94 F) | 4 | 44 | 2.9 +/- 0.15 | 60 |
| 32.2 C (88 F) | 10 | 53 | 2.8 +/- 0.10 | 53 |
| 26.7 C (80 F) | 5 | 56 | 3.9 +/- 0.11 | 52 |
| 21.1 C (70 F) | 10 | 46 | 7.2 +/- 0.23 | 54 |
| 16.7 C (62 F) | 3 | 35 | 17.1 +/- 0.38 | 53 |
Percent mortality, average development time (days) and average degree days required for development of NOW pupae at 10 constant temperatures *2
| Temperature (C) |
Percent Mortality |
No. Surviving |
Avg. time (days) +/- SD |
Avg. Degree-Days |
| 37.8 C (100 F) | 100 | 0 | ||
| 36.7 C (98 F) | 28 | 29 | 6.3 +/- 0.28 | 150 |
| 34.4 C (94 F) | 2 | 63 | 5.9 +/- 0.36 | 127 |
| 32.2 C (88 F) | 6 | 58 | 6.0 +/- 0.39 | 116 |
| 29.4 C (85 F) | 3 | 62 | 6.6 +/- 0.40 | 108 |
| 26.7 C (80 F) | 6 | 60 | 8.1 +/- 0.42 | 112 |
| 25.6 C (78 F) | 3 | 33 | 8.2 +/- 0.34 | 104 |
| 23.9 C (75 F) | 0 | 24 | 9.5 +/- 0.40 | 104 |
| 21.1 C (70 F) | 5 | 37 | 14.0 +/- 0.49 | 115 |
| 16.7 C (62 F) | 2 | 39 | 33.5 +/- 1.28 | 127 |
In mummy Payne walnuts it took a mean of 621 degree-days for male NOW and 646 degree-days for female NOW. *3
Feral NOW moths required 608 degree-days for males and 626 degree-days for females. *3
NOW moth migration appears to be limited to distances of 0.5 kilometers based on the studies of the insect’s dispersal in almond orchards. *3
NOW has no diapause and is active throughout the year if conditions are favorable. All larval and pupal stages of the NOW are known to overwinter. *3
The NOW has 5 to 6 larval instars during development, depending on the quality of food source. *3
NOW eggs are laid singly with an average of 85 eggs laid per female NOW. *3
Calendar date and NOW oviposition on egg traps in walnuts *3
| Oviposition Event First Egg |
50% Egg | Variety Year 1987 |
| 4/13 | 6/5 | Payne |
| 4/3 | 7/10 | Serr |
| 4/7 | 5/13 | Hartley |
| 4/4 | 5/5 | Serr |
| 3/29 | 5/21 | Payne |
| 3/24 | 6/14 | Serr |
| 3/24 | 7/13 | Payne |
| 3/24 | 5/23 | Ashley |
| 3/31 | 6/3 | Payne |
Length of female NOW life following mating 2 to 12 days. *4
Length of oviposition period of NOW female 1 to 9 days. *4
Number of eggs laid per female NOW, Range 3 to 244, Mean 84.6. *4
All done in July and August in outside temperatures in the Sacramento Valley.
Number of Days Following Emergence that Males and Females will Mate and period of Highest Frequency of Mating *4
| Total Individuals | Number of Individuals Mating on Indicated Days after Emergence | ||||||||
| Male | Female | First Day | Second Day | Third Day | Fourth Day | ||||
| M | F | M | F | M | F | M | F | ||
| 27 | 27 | 13 | 10 | 11 | 12 | 2 | 2 | 1 | 5 |
Done in July and August in outside temperatures in the Sacramento Valley.
Optimum laboratory development time of NOW on almonds and walnuts is 26 to 43 days at 27.5 C and 95% relative humidity. *5
Using the Horizontal method - Mean developmental time for NOW on mummy nuts is 1,025 degree days, and on new crop nuts 692 degree-days. Mean egg hatch is 100 degree-days. Lower threshold at 55F and upper threshold at 94F. *6
Using the Vertical method – Mean developmental time for NOW on mummy nuts is 1,092 degree days and on new crop nuts is 738 degree days. Mean egg hatch is at 100 degree days. Lower threshold at 55 F and upper threshold at 94 F. *6
NOW abundance is low in figs during the second flight in June and July. *7
NOW larvae may develop at different rates on old-crop and fresh-crop figs as it does in mummy and new crop almonds. * 7
In studies with female NOW oviposition onto egg traps in almond orchards it was found that with a gentle breeze most movement and oviposition was upwind (90%) and occurred within 116 meters (about 125 yards) of the release site. *8
The generation time of NOW in pistachios is twice as fast as in almonds, 835 degree days in pistachios versus 1,511 degree days in almonds. *9
There are four NOW flights in pistachios. *9
Degree Days are dynamic rather than static. They are accumulated at different rates depending upon time of year and in county (Location within the San Joaquin Valley). The following is an illustration of egg hatch in Kern and Madera counties using 100 Degree Days and a six year average of temperatures. * 10
Kern County: An egg laid on February 1 will hatch March 13 (41 days).
An egg laid on March 1 will hatch March 23 (23 days).
An egg laid on March 15 will hatch March 31 (16 days). *10
Madera County: An egg laid on February 1 will hatch March 21 (49 days).
An egg laid on March 1 will hatch March 31 (31 days).
An egg laid on March 15 will hatch April 7 (23 days). *10
Kern County may have as many as two more generations than Madera County. *10
In Madera County all eggs laid after September 23 contribute to the overwintering population. *10
In Kern County all eggs laid after September 28 contribute to the overwintering population. *10
One pound of pistachios equals 300 in shell nuts
One pound of almonds equals 184 in shell nuts
One pound of walnuts equals 50 in shell nuts. * 11
For every successfully overwintered NOW female , 85 to 100 eggs are produced in the spring.
NOW can complete their life cycle on pistachio nuts in 15 days or 500 Degree Days.
After much research winter sanitation is still the most effective means of control of NOW.
There is greater and earlier emergence of NOW on bare ground and in cover crops than disced crops.
Discing (regular not deep) is the best method of control.
A disc followed by a flail or roller. * 11
References
| 1- | University of California State wide Integrated Pest Management Project, Phenology Model Database – Navel Orange Worm. |
| 2 - | Sanderson, John Philip, “Synthesis of a Thermal Summation Model for the Development of the Navel Orangeworm on Almonds in California, phD thesis UC Riverside, March 1986. |
| 3 - | Shelton, Mark Douglas, “Navel Orangeworm Development in Mummified, Sunburned and Walnut Husk Fly Damaged Walnuts”, phD Dissertation Utah State University, 1989. |
| 4 - | Wade, William H. “Biology of the Navel Orangeworm on Almonds and Walnuts in Northern California”, Hilgardia, Vol 31 No 6, October 1961. |
| 5 - | Kuenen, Lodewyk, “Contributions to the Knowledge of the Biology and Management of the Navel Orangeworm in Almond Orchards of California’s Southern San Joaquin Valley”, MS Thesis, UC Riverside, March 1978 |
| 6 - | Zalom, Frank. “Navel Orangeworm Phenology”, Statewide IPM Project UC Davis, undated. |
| 7- | Burks and Brandl, “Seasonal abundance of the navel orangeworm in figs and the effect of phripheral aerosol dispensers on sexual communication”, Journal of Insect Science, 2004 |
| 8 - | Curtis et al… “Disruption of Navel Orangeworm Mating in Large-scale Plots with Synthetic Sex Pheromone”, Hort Crops Research Lab, ARS, USDA, Fresno, California in Journal of Economic Entomology, 78: 1425 to 1430, 1985 |
| 9 - | Cavanaugh and Beede, “Advancing Navel Orangeworm Control in Pistachios”. Pacific Nut Producer, March 2006. |
| 10 - | Siegel, Joel. Pos-harvest use of biological and chemical agents to control Navel orangeworm in pistachios”, USDA/ARS. Parlier, California. Handout at Pistachio Day 2007. |
| 11- | Pacific Nut Producer Magazine, December 2007. Bob Beede Pistachio Column Pages 18 to 20. |