David Doll2 CommentsJuly 18, 2013Insects

Speed Doesn’t Kill (Part Two)

Ken Giles and colleagues have been reworking some of the old research on spray rigs, coverage, and insect control. Their most recent project reviewed ground speeds on insecticide coverage, but with a new twist – they incorporated spray efficacy (NOW control) into the control. In their most recent study – reported in the 2011-2012 Annual Research Report of the Almond board of California – they showed that coverage did not differ between two rig speeds, but survival of navel orange-worm (NOW) eggs decreased when Altacor was applied at the slower speed. The study was conducted at Nickels Soil laboratory near Arbuckle, CA. Sprays were made at either 1.8 mph or 2.4 mph using Altacor insecticide, R-11 non-ionic surfactant, and micro-nutrient tracers for disposition analysis. Applications were made with 100 gallons/acre. This volume was chosen because previous studies has shown it to the most effective volume in reducing insect infestation/damage. Disposition was measured using steel cylinders which had some resemblance of almonds within the trees. Leaf punches were also taken to measure disposition on leaves. After spraying, nuts were collected from the upper and lower canopy and NOW eggs were placed to determine efficacy of the pesticide application. Nuts were collected 1 DAT and 14 DAT. Spray deposition was not affected by tree location (upper v/s lower) and speed. Secondly, there were no difference between NOW survival in the nuts collected 1 day after treatment among the tree locations and speed. 14 days after treatment, however, significant differences in NOW survivability were found in the upper canopy of the tree – the slower rig speed reduced egg viability by 95.75% compared to 87.12% reduction at the faster speed. In other words, NOW eggs were 3 times more likely to survive in the upper canopy when the pesticide was applied at the

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David Doll3 CommentsNovember 30, 2012Insects

The Importance of Winter Sanitation

2012 was a bad year for navel orangeworm (NOW). This was due to a lot of factors, which include:  Mild winter temperatures in 2011/2012, leaving a high overwintering population of NOW; Dryer in-season conditions in 2011 that made it harder to shake the nuts from the trees; Lack of winter rains reduced the ease of removing mummies; Poorly timed hull-split sprays; and a slightly above average temperatures through the growing season,  increasing degree days, which reduced times between NOW generations, increasing populations.

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Franz Niederholzer0 commentsAugust 17, 2012Insects

Hull split spray(s) for pollinators

Nonpareil harvest has been going for more than a week in the south Sacramento Valley. The third generation of navel orange worm (NOW) eggs are beginning to appear on egg traps in the region. As the Nonpareil nuts hit the ground, NOW female moths will find other places such as pollinator variety nuts to lay their eggs. So, pollinator nuts, especially in varieties like Monterey, can be damaged by NOW once hull split begins in that variety. In areas with high NOW populations, it may be worth considering spraying one or more pollinator varieties when hull split begins to reduce worm damage (click here to see an earlier post on hull split spray timing).        Spray timing for pollinators depends many factors including timing of NOW egg laying, Nonpariel harvest timing, and material choice. The county ag commissioner’s office tells me that, for purposes of determining spray timing based on PHI, harvest begins when the crop leaves the tree and ends – for that variety — when that crop leaves the orchard. If a pollinator variety is showing hull split before the Nonpareil are shaken, NOW are laying eggs, and the decision to protect the pollinator nuts is made, a spray should go on before the Nonpareil nuts are harvested – at the legal PHI – to give the best possible worm damage reduction. Previous spray history (Were the Nonpareils sprayed? When was that? What was the material?) will influence the spray timing as well.   Almond growers have a variety of pesticides available to reduce NOW damage and those materials have a wide range in PHI (see table below). Short PHI pesticides generally have shorter residual in the field, but those materials may have a fit in NOW management in pollinators, especially when working around Nonpareil harvest. Short residual

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David Doll4 CommentsJuly 15, 2012Insects

Timing of Hull-Split Spray – IGRs v/s Pyrethroids

There have been a few questions about the timing of hull-split sprays with the various products available. Our suggested timing for the spray depends on the product planned to be used. Insect growth regulators (IGR) (i.e. Intrepid, Success, Altacor, Belt, etc) should be applied at the onset of hull-split – just as the suture becomes defined and the nut pops open when force is applied. This is about the same time that the blanks begin to split in the tops of the trees on the outside rows. This timing is in contrast to the application of pyrethroids. These products (i.e. Asana, Pounce, Warrior, etc.) should be applied later than an IGR, around 2-5% hull split. The timing difference is due to the differences in activity and persistence of the products. IGRs tend to be more effective in controlling eggs, neonatal and developing larvae, while pyrethroids do a better job in knocking down adults moth populations. The activity of the IGRs also tends to persist longer in the field. Since the IGR has longer persistence and tends to target the developing larvae, it has to be present on the almond surface before the egg hatches/larvae continues to develop. Since these sprays are going out earlier than in the past, bracket sprays may be needed within areas with high NOW pressure. This is an important consideration if dealing with later harvesting varieties which will be exposed to the later flights of NOW.

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David Doll2 CommentsOctober 28, 2011Insects

Late Season Varieties and NOW Infestation

I am getting several reports from consultants, growers, and processors of high percentages of Navel Orange Worm (NOW) damage on the late harvested almond varieties. These reports have varied, but in all cases, damage has exceeded the targeted rejection rate of 2%. This has caught many people off guard. So, why did this occur? The cooler spring weather experienced meant a delayed hullsplit and harvest. This delay was most pronounced within Monterey and Fritz, which were about two to three weeks behind the “normal” harvesting time.  Harvest was delayed further by the early-October rain event. This increased “hang time” of the almonds within the tree provided the opportunity for more NOW damage. These varieties were exposed to the 2nd flight (during hullsplit), the 3rd flight (during harvest and drying), and 4th flight (during drying) of NOW which led to a greater rate of infestation. Since most growers applied a single NOW spray timed at 5% of Nonpareil hullsplit, these varieties were not only exposed to high populations of NOW, but were left without any type of chemical protection. A second NOW spray timed for the hullsplit of the Monterey and Fritz would have provided effective NOW control.  Egg trap monitoring would have indicated the need to spray at this time. Keep in mind that NOW develops more quickly on new crop than on mummies. It is also important to note that almonds are still susceptible to NOW infestation even after shaking. Increased time on the ground from poor drying conditions have also played a part in increasing the levels of infestation. Shook almonds were also exposed to the 3rd flight of NOW as well as a partially emerged 4th flight, and may partly explain the high number of young larvae within the hulls and kernels. Earlier this year, Walt Bentley, UC

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David Doll0 commentsJuly 14, 2011Insects

Timing of Hull-split sprays for Navel Orange Worm

Written by Walt Bentley, UC IPM Specialist, San Joaquin Valley. Hullsplit of Nonpareil almond, the most susceptible cultivar to navel orangeworm (NOW), is almost 2 weeks behind schedule in the central San Joaquin Valley.  Interestingly, the development of the second generation of NOW is not behind schedule with eggs being laid during the first week of July (see figure below).  This presents an interesting situation.  I believe many of these eggs will result in suicidal emerging larvae, not being able to infest the nut meat until hullsplit occurs.  This, however, doesn’t mean we are home free concerning NOW infestation.  It points to the importance of timing sprays to the development of the susceptible stage of the nut (initiation to 5% hullsplit).  Such timing will optimize the effects of any insecticide applied with the residual remaining through the complete second generation egg laying.  I believe a good portion of the early second generation eggs will hatch and be unable to infest the nut.  The remainder of the generation, that can reach the nut meat, will be shorter in time duration than normal.  If sprays are timed correctly, excellent chemical control should be achieved.  The same scenario that could optimize control of NOW in Nonpareils may result in making later splitting varieties such as Carmel, Sonora and Price more susceptible.  This is a scenario that we see from time to time.  Here the third generation eggs may be timed to Carmel hullspit resulting a greater potential for infestation.  Try to focus on early harvest of any late soft shell variety.  It may still be a good idea to monitor egg traps to see how NOW egg laying coincides with the hullsplit of these later soft shell varieties.  This can give you an idea if additional chemical control may be needed. 

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