David Doll0 commentsJanuary 12, 2017General, Horticulture, Weeds

Dormant Practices and Wet Weather

Over the past week, a lot of rain has fallen across California. Orchard access should be limited during periods of wet soil to reduce soil compaction as well as stuck equipment. Limiting access, however, creates challenges in performing a variety of orchard operations, including the list below.   Winter Sanitation. Removal of almond mummies from trees is critical for Navel Orangeworm management (NOW). Many operations usually wait for the first rains to help with leaf drop and to help “loosen” the mummies. In wet years, however, it becomes difficult to winter shake the trees as orchard conditions remain too wet for access of shakers. Furthermore, the “window” to winter shake is limited on the late end as fruit bud loss increases as trees enter delayed dormancy and buds swell (Mid to late January, depending on location). To manage this limited access, operations should consider poling crews. If these aren’t available, and sanitation is not performed, a spring timed (usually late April through early May) insecticide can reduce overwintering NOW. This strategy is not as effective as winter sanitation, but is better than doing nothing. Insecticide sprays targeting NOW in the dormant period are NOT effective due to NOW pupae being inside of the almond mummies. Planting bare root trees. Hand planting crews have an easier time than machine planting due to limited field access. If planting delays occur, trees should be placed into cold storage at the nursery as soon as possible to reduce the risk of leaf out and weakened trees. Keep trees in cold storage until ready to plant. Unless there is no other option, do not take delivery of trees in bins or plant them in a temporary location at the farm. On delivery, check tree roots to make sure they are healthy and living (should be

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Roger Duncan0 commentsJanuary 24, 2015Diseases

Dormant Sprays Not Reducing Lower Limb Dieback

Lower limb dieback (LLDB) continues to be a problem in some area almond orchards, especially in the Padre and Butte varieties.  Beginning in late April or early May, leaves on affected lower limbs begin to yellow and then turn brown.  Eventually, entire limbs die and by late summer, significant death of lower canopy wood can occur. Early studies indicated that species of Botryosphaeria and Phomopsis fungi played a significant role in this problem, but later efforts indicated that LLDB may not be a disease at all.  Multiple spring fungicide applications did not reduce limb death.  The bottom line is that LLDB is still not well understood although a compromised root system, especially from overly wet soils in the spring, may contribute to the problem. 

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David Doll4 CommentsJanuary 14, 2014Horticulture

Almond Dormant Oil Applications and Dry Conditions

There have been several questions over the past two weeks regarding applications of dormant oil onto almonds. Concerns of phyto-toxicity or oil burn have been raised over the dry weather, lack of rain, and lack of moisture within trees. Although the exact conditions that will favor oil burn in almonds is unknown, the following are a few considerations when making this decision.

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David Doll2 CommentsJanuary 15, 2013Diseases

Chlorothalonil and Oil: Dormant Application Q&A

I have been receiving quite a few questions about the application of chlorothalonil and oil. This dormant spray has been shown to be highly effective in reducing in season scab, as well as delaying the sporulation of the pathogen, making in-season fungicide sprays more effective. Q. The work by Dr. Adaskaveg shows 6 pts, the product is only registered for four (winter, 2013)…is the 4pt rate effective?

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David Doll0 commentsFebruary 2, 2012Diseases

Chlorothalonil and Oil for Scab Control — To Late? Yes.

Figure 1: The effect of dormant treatments on the incidence of almond scab sporulation. Observations were made on May 3rd, 2011. Different letters indicate significant treatment differences at p<0.05. There has been quite a bit of talk about the use of Chlorothalonil and oil applied during dormant for Scab control. Although this treatment has shown to reduce overwintering scab populations and delay scab lesion sporulation (Figure 1), caution needs to be taken when considering application. This product needs to be applied when the tree is completely dormant. Once the tree starts to push and the buds begin to swell/green tissue appears at the tip (Figure 2), avoid using this spray treatment. Chlorothalonil mixed with oil applied to green tissue will kill the green tissue, explaining why this product is labeled for dormant use no later than December. Figure 2: Delayed dormant stage of an almond bud. Note the bud swell and exposed green tissues. If a dormant scab treatment is to be applied at this time (delayed dormant/bud swell), consider making an application of copper and oil. This treatment has also been shown to be quite effective (Figure 1), especially when used in combination with in-season scab sprays timed 2-5 weeks post petal fall.

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David Doll2 CommentsDecember 11, 2011Diseases, Insects

Dormant Spray Considerations for Almonds

Scab lesions on green wood of almond. Being one of the quieter times of the year, the dormant period is a prime time to assess orchard issues and begin applying strategies to reduce various diseases and insect pests. Surveying the orchard and sampling new growth and spurs can help identify problems of scab, San Jose Scale, Navel Orange Worm, and mites. If populations are high enough, dormant strategies can be applied to reduce the damage to the upcoming season’s crop. Scab. If a scab outbreak and the corresponding mid- to late-season defoliation were experienced this past year, a dormant/delayed dormant application of copper and oil should be considered. This spray is effective in reducing and delaying sporulation of scab twig lesions, thus reducing in-season disease incidence. It should be used in combination with properly timed bloom and petal fall sprays. Based on field observations, orchards with significant scab outbreaks in 2010 that followed the above recommendations had obvious suppression of the disease in 2011, and were able to keep the leaves on the trees until late November. Red Halos caused by San Jose Scale feeding/infestation in almond. Insect Pests. Spur samples should be selected throughout the orchard to determine the presence of San Jose Scale (SJS), European Red Mite (ERM), and Brown Almond Mite (BAM). Spurs should be pulled from a main scaffold with 100 spurs samples from the orchard. If 20% of the spurs selected are infested with scale, then a one-time oil application at 6-8 gallons per acre should be applied. If over 60% of the spurs are infested, the oil application should include an insect growth regulator that targets SJS. It is important to control SJS as high populations can kill spur wood, reducing crop load. Obvious signs of scale infestation include a red halo found on

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David Doll0 commentsApril 6, 2011Diseases

Late Scab Timings for Almonds

Early season Scab lesions on almond. We are approaching the end of the effective almond scab control spray timings. Scab has become more common in area orchards due to the increased planting density and occurrence of wet springs. Causing defoliation in late summer, this disease can weaken the tree, reducing crop for the coming years. A heavily infected orchard will have persistent scab issues for several years after the disease flare up. Fritz and Carmel are more susceptible to this disease than Nonpareil and other varieties This spray period starts at about 2 weeks after petal fall and continues to about 5 weeks after petal fall. Years of research by Dr. Jim Adaskaveg and Dr. Brent Holtz have demonstrated that spraying during this period provides the greatest control. The use of strobilurins (FRAC 11 – Gem, Abound, Pristine) provides the greatest control of this disease, followed by the DMIs (FRAC 3 – Quash, Inspire, Inspire Super, Bumper, Tilt), Topsin-M (FRAC 1), and broad spectrums (Captan, Maneb, Ziram, etc). Overwintering scab twig lesions. It is speculated that strobilurin resistant populations of scab are becoming more common. Applying back-to-back applications of strobilurins will hasten the development of resistance. If you sprayed a strobilurin earlier this bloom season you must consider another mode of action for scab control. Earlier entries emphasized the importance of saving this mode of action for summer diseases.  Sprays must be made within the 2 – 5 week petal fall period to provide maximum control. Later sprays will not be as effective. Waiting till the disease is visible before you start to spray is not advise as the population at that point is too high to control. In many cases, spraying at this point will only waste money AND increase the risk of fungicide resistance.  Orchards with severe outbreaks should consider a dormant application of copper/oil to

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David Doll2 CommentsNovember 16, 2010Diseases, Insects

Preparing for the Dormant Period

Just returned from a field day meeting held near Firebaugh discussing pest and disease management strategies for the upcoming dormant season. I thought I would highlight a few points from the talks by Walt Bentley (UC IPM), Mario Viveros (Emeritus UCCE Farm Advisor – Kern County), and myself – David Doll (UCCE Farm Advisor – Merced County). I apologize for the brevity of the entry as I am preparing for a field trial due to be fumigated next Monday. Navel Orange Worm (NOW): Winter sanitation is critical to help reduce the overwintering population of NOW. In general, no more than two mummies per tree should be left in the tree. With some growers, complete removal of the mummies is performed. Most growers remove mummies. This is easily done on younger trees. As the trees mature and become larger in size, the task of sanitation becomes difficult, resulting in more mummies remaining within the upper canopy. This may explain why many growers see more NOW damage in mature blocks. Even though the trees may appear to be clean, a closer look usually reveals mummies still hanging in the tree. Peach Twig Borer (PTB): Scouting for hibernacula should be performed. There are several treatment options and timings for PTB. These include dormant oil sprays, bloom sprays with reduced risk products, and May sprays. See the PTB page on the UC IPM website for more information. Mites: European Red Mite and Brown Almond Mite will overwinter as eggs around the base of spurs. Spur sampling, which should also be done for scale, can help determine if treatment is needed. An oil spray outlines at the Mite page on the UC IPM website will suffice for most locations. Scale: The dormant period is the easiest time to treat for scale. Spur sampling can help determine the treatments needed. Check here for

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Franz Niederholzer1 CommentJanuary 18, 2010Insects

New pesticides are effective on Peach Twig borer in early sprays

Author: Franz Niederholzer, UC Farm Advisor Sutter-Yuba Counties Peach twig borers (PTB) are a key pest of almonds. Nuts damaged by PTB are preferred feeding sites of navel orangeworm (NOW). At a recent almond IPM meeting in the San Joaquin Valley, a leading independent PCA told the audience that a good NOW program included PTB control. Talk with your PCA and review reject sheets and moth traps to decide if PTB control is needed in your orchard. Dormant, delayed dormant, or bloom sprays (See this article about insecticides at bloom), with the proper pesticide, give effective PTB control when applied properly (every-row spraying and proper sprayer speed). Other effective timings include a spring or summer spray(s) timed using moth trapping data and degree days. Recently registered pesticides give excellent PTB control in research by Dr. Frank Zalom, UC Davis Entomology Department, in the Sutter/Yuba region (see table below). These materials are less toxic to operators and wild life, especially those that live in water. Consider these new materials as part of a PTB control program in your orchards. Organo-phosphate pesticides (Lorsban, diazinon, etc.) and pyrethroids (Asana, Warrior, Brigade, Baythroid, Mustang, etc.) are very effective on PTB, but can harm fish and other life in local streams if the pesticide moves to the water in drift or water runoff from rain or irrigation. Including a new pesticide in your PTB program in dormant to bloom also helps avoid pest resistance to organo-phosphates and/or pyrethroids.

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David Doll7 CommentsDecember 21, 2009Nutrient

Making a Zinc Dormant Spray

Question came in this week regarding the decision on the timing of a zinc spray. When should I make a Zinc Spray?Research by UC Specialist Dr. Scott Johnson at the Kearney Agricultural Center has shown that a zinc foliar spray is the most effective when made during the post harvest period. Applications of zinc should be made to the tree around late October – early November. The idea is to have a leaves still on the tree when the application is made. Dr. Johnson has shown that a roughly 3% of the zinc applied is taken into the tree from a fall foliar spray, but this is dependant upon the source of zinc. Defoliation may occur after the application, but do not worry as sufficient zinc should have made its way into the plant tissues. Is making a dormant zinc application a bad idea?If a fall application of zinc was not made and the orchard is suspected to be deficient in zinc, making a dormant application of zinc will increase zinc tissue levels. The percentage of uptake is slightly less, around 2.0-2.8%, and it is harder to get a large amount of zinc into the tree. This is due to the fact that the shoots, buds, and bud scars only account for roughly 3% of the surface area of a peach/almond branch. Therefore the amount of spray landing on the tree surface is significantly less than when the leaves are still attached (Leaves make up the other 97% of the surface area). To counter this, higher rates should be used during the dormant period. What type of material should be used in a zinc spray?Dr. Scott Johnson’s (UC Specialist) work has shown that the “biggest bang” for your buck comes from Zinc Sulfate (high uptake, moderate phytotoxicity). There are other

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