David Doll4 CommentsFebruary 9, 2020Diseases, Horticulture

2020 Bloom Considerations

As the 2020 almond bloom/crop year begins, there are several considerations to keep in mind. These points may be useful to help understand observations from the field as well as provide an understanding of any direction received. Nut set. Flower set percentages will vary from year-to-year. For mature trees, about 20-30% of the flowers will set while younger trees will be slightly higher. Even though this is low, crop loads are still high due to the number of flowers that are in each tree. A mature tree will have an estimated 35,000-50,000 flowers, depending on tree size. For more information on this, please see this article: https://thealmonddoctor.com/2016/03/07/almond-set-and-nut-drop/ which discusses the results of a tagging study which followed the development of almonds through the season. External factors greatly influence the set percentages. Crop load from the previous year impacts the amount of energy available for flower formation and bloom. High yields from the year before will reduce the number of flowers that will set nuts. Poor weather conditions can reduce bee flight hours, kill flowers in freezing temperatures, or promote disease. The period of weather risk extends into the fertilization period, which continues for several weeks. Keep in mind that the crop is susceptible to frost and diseases as long as there is a risk of frost and rainfall.   Several factors can be mediated by good farming practices. These include the presence and strength of pollinators (usually honeybees), post-harvest practices, and nutrient deficiencies. Honeybees are required for varieties needing cross pollination (most CA orchards – 2.0-2.5 hives/acre) and recommended for self-compatible varieties (0.5-1.0 hive/acre, although the exact number is unclear). Stronger hives (8+ filled frames) are essentially an insurance policy for poor weather conditions. Hive numbers and placements should take into account the weather. Post-harvest treatment of the trees is

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David Doll6 CommentsFebruary 6, 2019General, Horticulture

2019 Almond Bloom Considerations

Almond bloom is just around the corner. This “start” to the season is an important period for almond production as flowers require reasonable weather conditions for pollination, fertilization, and eventual fruit set to occur. With that in mind, below are a few considerations for this period. Rain or conditions favoring dew can increase the amount of disease. Pathogens affecting almond flowers are ubiquitous in the environment, and therefore the condition that influences infection are periods of leaf wetness. Fungicides should be applied to protect the flowers from rain-splashed spores and subsequent infections. Newer class fungicides can move into the upper cell layers of the flower and kill infections, but this “reach-back” potential only provides about 2-3 days of “cure” after a rain event. Start the spray program with fungicides that are most effective for blossom diseases, but provide limited protection for petal fall and spring-time diseases. This typically includes the FRAC groups 1 and 9. As bloom progresses into petal fall, other fungicides should be considered to manage anthracnose, green fruit rot, shot-hole, and scab. FRAC groups 3, 7, 11 or combinations of these products should be considered. Remember to rotate away from fungicide FRAC groups used in previous sprays. This will help reduce the formation of resistance within pathogens, increasing the “shelf life” of a fungicide. To assist with this, especially if rainy conditions are expected, consider utilizing a broad spectrum material at petal fall or shortly after this period to provide the ability to use strobilurins and DMIs (FRAC 11 and 3) for scab and rust control. Some good rotational, broad spectrum products include chlorothalinil (FRAC M5), Ziram (M3) or Captan (M4). Don’t forget about the bees. Honeybees are brought into the orchard to provide pollination services – a requirement for production for most California type almond varieties

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David Doll2 CommentsFebruary 9, 2017Diseases

Almond Bloom 2017

Almond bloom is approaching fast. Based on local conditions and projected warm weather next week, bloom will probably be within 7-10 days. Conditions this year are wetter than they have been in the past which will be conducive to many almond diseases, including brown rot, shot-hole, anthracnose, and jacket rot. Furthermore, orchard access may be limited, reducing the ability to apply fungicides by ground rigs reducing coverage. Below are a few points to consider as we begin the 2017 season. Be prepared for several fungicide sprays. If wet conditions persist, a more conventional bloom spray program should be considered with an application around pink bud to 20% bloom,  an application at 80% bloom, and a petal fall spray. These regular sprays ensure coverage of the expanding floral tissues. Sprays should be made every 10 to 14 days in consistent rain, and every seven to ten days if  heavy rains are experienced.   Fungicide rotation is critical. With multiple fungicide applications, each successive spray should be a different fungicide mode of action. This is represented by the FRAC number. If using multi-mode of action fungicides, the fungicide used in the follow up spray needs to be different than both modes of actions utilized in the previous spray. Please review the modes of action for the various diseases and timings by using the Fungicide Efficacy tables outlined here. Almond relevant information is on page 31. Often wet winters are followed by wet springs. With the potential need of fungicides through the spring, it may be useful to mix in a broad spectrum fungicide at petal fall. This would provide the ability to apply the same mode of action twice in the same season. A spray program with this type of rotation could look like this: Pink bud: FRAC 9; Full Bloom: FRAC 3/11; Petal Fall:

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Emily Symmes2 CommentsJanuary 24, 2017Diseases, General, Insects

Protecting Honey Bees During Bloom

Written by Emily J. Symmes, UCCE Sacramento Valley IPM Advisor With almond bloom on the horizon, it is time to revisit best management practices for protecting pollinators (e.g. honey bees) during this critical time. Remember that communication is key during the bloom period. All parties should be kept informed so that beekeepers are aware of impending applications and applicators are aware of the requirements related to notification, materials, timing, location, and method of application. This includes growers, beekeepers, land owners-lessees, PCAs/CCAs, pesticide applicators, and county Agricultural Commissioners. General guidelines: Employ sound IPM practices: Apply pesticides only when absolutely necessary based on monitoring and treatment thresholds. Know all of the available materials and application timings. For insect pests, there are effective alternative timings for insecticide applications aside from the bloom period. If the weather remains dry and clear throughout bloom, there should be minimal need to apply bloom fungicides. One solid application just ahead of full bloom should be adequate for good disease control under these conditions. Earlier spray timings (e.g. pink bud) if wanted, may be applied every-other-row. Be aware of the impacts of any treatments on pollinators and other non-target organisms. Always provide adequate clean water for bees: Cover or remove water sources prior to any application. Keep water clean and fresh ensuring bees spend more time pollinating the crop than searching for water. Bees can forage up to 5 miles away seeking food and water if not available in the orchard, increasing their risk of contact with harmful pesticides. Do not spray hives directly with any pesticide. Ensure the spray-rig driver turns off nozzles when near hives. Do not spray flying bees with any applications. Aside from toxicity concerns, bees will not be able to fly because of the weight of spray droplets on their wings. Even water

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David Doll8 CommentsFebruary 15, 2016Horticulture

2016 Almond Bloom Considerations

Adequate chill and recent warm temperatures have accelerated almond bloom. Timing is close to “normal” in southern and southwestern areas of the State, but are 1-3 weeks ahead further north. Below are some thoughts to keep in mind with the anticipation of rain this week. Authors note (2-16-2015): There has been some concern about the wording around the time of nutrient/boron sprays and bloom. Research has shown that boron applied postharvest to 10% bloom can increase yield, while applied later than 10% bloom will not have an impact. Nutrient sprays-with the exception of boron as described in the previous sentence- have not been found by researchers to increase yield when applied at bloom. Sorry for the confusion. Fungicides are usually effective for about 14 days after an application. This period of protection is decreased with rain events. Furthermore, as surface areas expands – whether it is the flowers or leaves – newly exposed tissues are unprotected from infection. This means that spraying too early may not provide the wanted protection. If planning to make a fungicide application, apply the material as close to the rain event as possible. Remember that it needs between 30-60 minutes to dry. Depending on the pre- and post-rain conditions, and the periods of leaf wetness, a fungicide spray may not be needed. Keep in mind that fungal diseases require several hour periods of leaf wetness – which comes from fog, dew, and rain. Be cautious with adding additional surfactants. Most fungicides have surfactants mixed with the active ingredient. Adding additional surfactants may impact the efficacy of the fungicide, damage the flower’s tender tissues, or impact bees. The label should indicate if a surfactant is needed. Avoid tank mixing in boric acid with sprays made during bloom when bees are active(1). Researchers at the University of California as well as around

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David Doll9 CommentsJanuary 30, 2015General, Insects

Honey Bee Considerations at Bloom

There has been a lot of concern about honeybee health related to fungicide and insecticide applications within orchards. More is being learned every year about the impacts of pest management practices on hive health. Recently, The Almond Board of California released an excellent resource titled “Honey Bee Best Management Practices for California Almonds.” This resource provides an overview of the research conducted and the recommendations generated from the results and conclusions. The following is a brief overview of these practices that are associated with insect and disease control around bloom: Read the pesticide label carefully – including surfactants – and avoid any chemicals that indicate toxicity to bees. Avoid applying or tank mixing any insecticides during bloom until the effects on bees are known. Treatments for peach twig borer should be considered prior to bee move-in or after hive removal (i.e. delayed dormant, “May” spray); Avoid the fungicides iprodione, captan, or ziram. These fungicides negatively impact bee hive health; Apply fungicides later in the afternoon or evening when bees and pollen are less present. It is also important to also not spray too late that the fungicide does not have a chance to dry before the next foraging day; Addition of adjuvants is not needed unless specified by the fungicide label. These compounds may harm bees by increasing fungicide activity; Cover or remove the bees’ water source and avoid spraying the hive directly with any pesticides. More information can be found at The Almond Board of California. Keep in mind that these spray practices are independent of good bee hive care, which includes provision of water in during dry bloom periods, sources of pollen.nectar in bee holding areas, and of course, good communication with your beekeeper.

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Franz Niederholzer3 CommentsFebruary 7, 2014Diseases, Horticulture, Insects

Pollen, Bees, R.U.L.E.S., and Almond Bloom

Almond bloom has begun.  No time of the season is more important to delivering a good crop.  You don’t get a Mulligan at almond bloom.  Good pollinization, delivery of viable pollen grains to the flower stigma of a compatible flower, is the first step of a successful bloom season.  Keeping spray materials off the pollen helps keep the pollen viable for germination (the next step in a good crop) and healthy for bees—the key pollinators from Red Bluff to Bakersfield.

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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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