David Doll4 CommentsJanuary 17, 2013Insects

IGRs at Bloom: Bad Idea?

Recent IPM practices have advised the use of IGRs (*1) diflubenzuron (Dimilin) at bloom time to control PTB larvae. This timing has been shown to be highly effective. Work by several scientists, including researchers from USDA-Tuscon Haydeen Bee Research Lab, Ohio State University, Oregon State University, BASF, and UC Davis (*2), however, has suggested that this may not be the best timing for bee health. Below is a email sent by Dr. Mussen for distribution. It basically concludes that the bloom timing for IGRs may harm bees, and should be avoided if possible.  Delayed dormant and May spray applications of these products can and should be considered for PTB control. Email from Eric Mussen, UC Entomologist/Apiculturist:

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Franz Niederholzer3 CommentsDecember 21, 2012Horticulture, Insects, Weeds

What did I learn at the Almond Board’s annual conference?

The Almond Board of California’s annual conference is a chance to connect with others in the almond industry, listen to world class researchers talk about their work, and check out a huge almond-focused trade show all at one event. The 2012 meeting was last week (Dec 11-13).  Here is a quick review of some of the things I picked up from researchers and informed industry members at that meeting…

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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 Doll0 commentsMay 4, 2012Insects

Considerations For Managing Ants In Almonds

Walter J. Bentley, Regional IPM Entomologist UC Kearney Agricultural Research and Extension Center Ant damage to almonds continues to be a difficult problem for farmers to manage.  In all areas of the state populations of the three species of ants which cause damage appear to be increasing.  From Fresno County going south to Kern County the California fire ant (also called the southern fire ant), Solenopsis xyloni, is the damaging species.  Another, less common species, is the thief ant, Solenopsis molesta, which is slightly smaller than Xyloni.  In Merced, Stanislaus, and San Joaquin Counties both the California fire ant and the pavement ant Tetramorium caespitum  can be found causing damage.  In the Sacramento Valley the pavement ant is the predominant species.  Although almond farmers will know, from past history of damage, whether or not they have a problem species in the orchard, there are other species that are considered more beneficial than harmful.  These include the bicolored pyramid ant, Doriomyrma bicolorand the native gray ant, Formica aerata.  This latter species has been found to actively feed on peach twig borer in unsprayed peach orchards.  The best way to separate the damaging species from those not causing damage is by examining the thin waist between the last pair of legs and the abdomen (stomach).  Both the pavement and the California fire ant possess two bumps or nodes while the beneficial species have only one node.  Also, the damaging species will often be found with weeds growing within the nest and are easily excited by disturbing the soil near their nests.  Finally, the pavement, California fire ant, and thief ant will aggressively bite and sting.  The California fire ant sting, in particular, is quite painful. While control information has applied to all three damaging species, monitoring methods and thresholds where only developed

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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 Doll2 CommentsSeptember 22, 2011Insects

Late Season Leaf Defoliation due to Web Spinning Spider Mites

A few farm visits and phone calls have been coming in over the concern of late season spider mites. In these orchards, mite populations have flared up, causing defoliation. These growers have been asking is they should spray for mite control. As always, the answer depends, but here are some thoughts to consider when making this decision: 1. Since harvest has been delayed, and many trees have experienced longer periods of water stress than normal. Tree stress attracts mites, which creates hot spots within weaker areas of the orchard. 2. Tree defoliation caused by mites rarely causes significant effects on next year’s crop. If defoliation occurs, some leafing out may be triggered by an irrigation. It is still advised to apply a post harvest irrigation even if the tree is defoliated. Damage is more significant on younger trees as loss of leaves in the fall reduces the amount of overwintering carbohydrates. 3. An application of a miticide should only be made in attempts to curb the population until cooler weather. In many cases it is not possible to control a flare up, but rather the application “buys time” until cooler temperatures/ less stressful conditions arrive. An application should be considered if the “hotspots” are starting to defoliate and the mites are moving outward into the orchard. 4. If mites are present, but very little defoliation is occurring, the best strategy is to “wait it out.” Some later season defoliation may occur, but the “damage done” would be minimal, thus not worth the time and expense of the spray. 5. Miticides to apply should target the adults stage. These include the products Acramite (bifenazate), Vendex (Fenbutatin-Oxide), and Desperado (Pyridaben/Sulfur). 6. It is very difficult to get effective coverage with a miticide spray due to the hydro-phobic nature of the webbing. Drive slow and use the proper rates

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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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