I have embedded my presentation from the 2010 Central San Joaquin Valley Almond Day meeting this past week. This presentation highlights many of the considerations that need to be made by growers in determining when to spray for navel orangeworm (NOW), what to treat with, and how frequently a spray should be made. I will discuss slides of interest which will hopefully provide some type of commentary as you view the presentation. This is a first, so bear with me...2010 NOW Management Considerations
Slide 1: Title Slide.
Slide 2: General introduction of pest lifecycle. For reference, if needed, please see IPM website. Important points to mention is that almond acreage has expanded closer to NOW original territory, and has provided a host density much greater (10,000 x greater) than the original host of NOW.
Slide 3: Control of NOW is based upon timing of application, coverage of spray, and persistence of the product within the orchard.
Slide 4: All of these factors influence NOW pressure and end of year damage. Varying degrees of sanitation among the pistachio, pomegranate, and fig growers - as well as almond growers - can carry over high populations of NOW into the next growing season. Early harvest can significantly reduce NOW damage as the nuts will be harvested and removed from the orchard before the third flight of the moth begins. Peach twig Borer damage can predispose a nut to NOW infestation - so effective PTB management is also part of effective NOW management.
Slide 5: Talking a little bit more about sanitation. Long term study showing the effect of sanitation on NOW damage at harvest. Note that winter shaking trees to less than 2 mummies per tree significantly reduces NOW pressure without a spray. This study was on the nonpareil variety. Hardshell varieties may not have similar results - BUT NOW from a hardshell orchard can move into neighboring orchards with Nonpareil.
Slide 6: Percentage of survival of nuts from different varieties infested with NOW. The almonds were infested in the field and brought into the lab - probably why the percentage is higher than expected. Note the differing rates and the high survival % within butte and padre. It appears that survival within Padre is within the hull of the almond, while the larvae survives in the nut of the Butte. Another reason why sanitizing/winter shaking those Butte/Padres is important for growers with other blocks/neighbors with NOW sensitive varieties.
Slide 7: Moths can overwinter and emerge from mummies at any time in the season. While most do emerge in the spring, there are significant amount of moths emerging in June and July as well. NOW is always emerging and present within the orchard!
Slide 8: Irregardless of the trap counts in the early season, it appears that NOW syncs up well with the timing of almond hullsplit. Joel Siegel, USDA-ARS researcher, has stated that it is almost like the almond was meant for the NOW - the two, albeit evolved thousands of miles away, have lifecycles that match up well.
Slide 9: Data showing that the newer "reduced risk" pesticides control as well as pyrethroids and organophosphates providing more options for growers.
Slide 10: Timing of differing products: Reduce risk products can be applied a few days earlier than pyrethroids. For the most part, reduce risk products should be applied on the early side of hullsplit - just around the time blanks start to open. Pyrethroids should be applied later at around 2-5% hullsplit. The difference is due to the persistence of each product within the feeding zone of NOW larvae and the ability to control NOW. The later timing for pyrethroids is due to their ability to knock down adult moth populations.
Slide 11 and 12: Research to show the persistence of various products for NOW control. These studies were from laboratory research and it is thought that product breakdown will be quicker within the environment due to UV light, temperature, and other factors. Take home message - Reduce risk pesticides appear to persist a day or two longer in the orchard.
Slide 13 and 14: Coverage differences with Spray rig speed - covered this topic in last weeks blog. Spray at speeds no faster than 2 MPH.
Slide 15: Slide discussing why bracket sprays are effective. Essentially as the nut splits, more and more surface area becomes available for NOW egg laying. Furthermore, it becomes increasingly difficult to cover all of the areas of the nuts when applying a pesticide. This is why for areas with high NOW pressure, a spray at early hull split and late hull-split will provide greater control than a single spray.
Slide 16: A slide re-iterating the opening comments about knowing the pressure within the orchard. Keep in mind that a well timed, single spray with a proven product applied at 2 MPH will only provide 50% reduction of NOW damage at harvest. If a 50% reduction does not get you below the 2% threshold, than re-evaluation of the listed orchard factors and a 2nd or 3rd spray may be needed.
Slide 17: Conclusions for the 2010 season. PTB 2nd flight appears - at this moment - to overlap with hullsplit. Usually when this happens, NOW damage % increases. If using a reduce risk product, spray on the early side of hullsplit. Generally, for growers in Merced County - with the exception of high pressure areas- one application (and in some cases no applications) should provide the needed NOW control. Keep in mind that pest management practices need to evolve as we find out more about this pest. It is prudent to consider applications of reduce risk sprays at May to help with NOW population. It may be, although we do not have the research yet to support this, that a single May spray with a non-pyrethroid reduce risk material may control NOW populations for the season. If a pyrethroid product is used within the orchard, a miticide should be added to control the corresponding mite flare up. For further info, please check the UC IPM webpage on NOW.
2010 NOW Management Considerations
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