David Doll12 CommentsJanuary 16, 2021Diseases

Almond Fungicides and Bloom: Plan Your Work, Work Your Plan

Planning your fungicide program has multiple benefits, and now is a good time to start doing so. Time can be taken to identify fungicides and respective modes of action to develop a proper rotation strategy. It allows the ability to price and compare differing options that may swap materials at specific points. Finally, it gives the opportunity to review the labels of the materials to determine application requirements, and the need to include (or most likely exclude) additional materials. To determine the year’s spray program, several things need to be considered. These include anticipated weather during flowering, disease history, materials available, operational tolerance to disease, and the ability to spray (budget constraints). Dry weather during flowering will reduce the need to spray, while free moisture from rainfall or humidity/fog can increase disease pressure. If dry conditions are present, fungicide sprays can be withheld until conditions change. In these types of years, bloom typically progresses rapidly, making it difficult to spray due to the shorter duration. As the flowering period ends and petal fall begins, it may make sense to consider a “clean-up” spray for any infections that might have occurred. Having a history of disease increases the presence of the given disease’s inoculum. This means that as soon as any rain event occurs, this disease will begin to spread at a higher rate. If dealing with a previous outbreak of a disease, especially diseases that form wood cankers (e.g. Anthracnose, Monolinia, Phomopsis, etc), fungicide applications should occur prior to going into any wet period, and re-application should be considered for any rain events that occur 10-14 days after the previous application. This may mean multiple sprays during wet years to reduce disease inoculum. As incidence decreases in future years, the spray program can be gradually reduced. Available chemistries for disease

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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 Doll3 CommentsMarch 6, 2013Diseases

Leaf Wetness is a Fungi’s Best Friend

I always start off most talks about bloom time and spring diseases with the concept of leaf wetness. Although it may seem over-simplified, without leaf wetness (and high humidity), foliar fungi are not able to infect the plant. Periods of leaf wetness are needed for several functions of fungal dispersion and growth. Windy, rainy weather blows spores from infected tissues to new, healthy tissues. Leaf wetness or high humidity provides favorable conditions for spore germination. Once inside the tissues, the pathogen may grow and reproduce faster in wet and mild weather.

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David Doll2 CommentsJanuary 27, 2011Horticulture, Nutrient

Bloom Spray Additives: Do they work?

Bloom is approaching. Several questions about whether or not bloom spray additives increase flower pollination and set have been asked. I will try and answer them the best I can using information from previous trials across the state. Much of this information is gleaned from Roger Duncan’s presentation delivered at the 2010 Stanislaus Almond Day. Should I include foliar nutrients in the bloom spray?Several trials from four different advisors from areas across the state (Duncan – Stanislaus, Holtz-Madera, and Edstrom – Colusa, and Viveros – Kern) have indicated that nutrients and other additives included with bloom sprays do not increase yield of almonds in properly maintained orchards. In most trials, yields of the untreated control were higher than the foliar nutrient applied treatment. These were multiple replicated trials held over several years. Materials used can be seen by viewing the presentation linked below. This trial data can be seen in Roger Duncan’s 2010 NSJV Almond Day presentation (click link). What about Pristine® Fungicide?Pristine® fungicides is a boscalid/strobilurin mixture that has been used successfully for several foliar fungi that commonly affect almond flowers and leaves (i.e. Brown Rot, Rust, Scab, etc.). There is evidence that suggests that Pristine® causes a yield bump when applied during the bloom or post bloom period. Research by Jim Adascaveg (UC Riverside) and Roger Duncan (UCCE Stanislaus) tested this hypothesis and have not found a significant increase in yield from a bloom or post bloom Pristine® application. It is important to state that in Duncan’s trials (Stanislaus Co.), the yields were higher in treatments containing Pristine®, although not statistically significant. Duncan found this same insignificant yield bump when applying Gem®, another strobilurin, in the post-petal fall period. Conversations with a local consultant indicated mixed success of the Pristine® yield bump across his multi-year trial. Although he

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Brent Holtz0 commentsFebruary 2, 2010Diseases

Bloom sprays: What and when to use to provide effective disease control.

Written by Brent Holtz, UCCE San Joaquin Almond trees are susceptible to bloom and foliar diseases when it rains at bloom, and the decision of when to spray and what fungicides to use can be quite difficult. In the San Joaquin Valley we are usually in a low precipitation region and we cannot predict when and how much it is going to rain. We often receive rain during bloom which can result in favorable conditions for several plant pathogenic fungi to cause spring time diseases of almonds. The main diseases in almonds are Brown Rot Blossom Blight, Green Fruit Rot or Jacket Rot, and Shothole. Other less familiar diseases include Scab, Rust, Leaf Blight and Anthracnose. The fungi that cause these diseases are usually always present in almond orchards, sometimes in higher or lower amounts depending on the previous year’s disease levels and current environmental conditions. Fungicide Control ProgramsGenerally, a good disease control program is based upon a wise choice of fungicides and good timing and coverage. Growers should assess the diseases present in their orchards and select materials carefully. Not all fungicides are equally effective on all diseases (fig. 1). It is a good idea to use more than one kind of fungicide for a broader spectrum of activity. This will be especially important with using Strobilurin fungicides (Abound, Cabrio, Flint, Sovran, and Pristine). Pristine is a Strobilurin fungicide that is combined with Carboxyanilide to slow resistance development. Resistance to these fungicides can develop over time and repeated use, thus try to rotate the fungicides you use. Two successive applications of the same mode of action should be avoided. Information on effective fungicide rotations can be found in figure 2. A suggested bloom spray strategy:Usually two sprays are made for brown rot control. The first is usually done at

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