Carpophilus Beetle: What We Know

Authors: David Doll and Zubair Shahzad Carpophilus beetle (Carpophilus truncatus) is a small insect that causes severe damage to almond kernels. The insect overwinters within the soil, and emerges infesting the almonds at hullsplit. They are quite mobile and able to fly up to 3 miles/5km to find a suitable host. Humid conditions increase the emergence and rate of development, leading to multiple generations within a season. More on Carpophilus beetle can be found here. Damage is highly dependent on the variety, harvest timing, and weather conditions. Soft-shell varieties with poor shell seal are most susceptible. Within Australia, the worse damage is reported on Nonpareil, with minimal damage reported on Monterey, Price, and Carmel. Infestation rates increase when harvest delays occur as the nuts are exposed to multiple generations. Rain between hull-split and harvest often increases damage as it results in a faster rate of insect development and harvest delays. Effective management depends on both chemical and cultural practices. In severely infested fields, operations have reported success of applying clothianidin at 1% hullsplit. Early harvest has been shown to reduce exposure and corresponding damage. Nonpareil harvest completion should be targeted by the end of August in the northern hemisphere/February in the southern hemisphere. Winter sanitation is critical to reduce Carpophilus beetle populations. Mummies serve as the initial food source for the beetles as they exit the soil. Operations should target <5 mummies per tree after sanitation. Nuts should be destroyed as soon as possible after winter shaking as the beetle emerges from the soil as it warms. Current trapping methods do not have a lure specifically for C. truncatus. General lures for Carpophilus beetles are available and can be used within bucket traps. Although not providing species level population dynamics, it can provide insight on the emergence of carpophilus beetles

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Preventing spring diseases in almond

Petal fall through the first few weeks of nut development is a critical time for disease management. During this period, the almond fruit, newly emerged leaves, and senescing tissues are susceptible to many diseases. These include jacket rot, anthracnose, brown rot, leaf blight, shot-hole, scab, and with Mediterranean varieties, red blotch. Protecting the developing fruits should be top priority through the early spring. Thorough disease control early in the season prevents the build-up of inoculum, reducing secondary spread of the disease. Typically, this is done with fungicides, which should be applied prior to rain events.  Sprays should be made every 14-15 days if rainy conditions persist, but this period can be extended if dry conditions occur. If using broad spectrum fungicides such as Ziram, Captan, or copper, the re-application interval should be shortened to 10 days in rainy conditions. The appropriate chemistry should be chosen to target the disease of concern. For example, triazole (FRAC 3) and strobilurin (FRAC 11) fungicides are not effective on botrytis jacket rot, but they do control other diseases well.  Additionally, fungicide chemistries, not commercial brand names, should be rotated to reduce the formation of resistance. This is because multiple commercial brand names may use the same fungicide chemistry. This process has been streamlined through the use of a FRAC number. This number indicates the mode of action of the fungicide, and use of the same number in back-to-back applications should be avoided. There has been increasing interest in biological products for control of diseases within almonds. Generally, these products work well in mild-to-moderate disease pressure years, control tends to be reduced in high pressure years(i.e. prolonged wet, rainy conditions). Some of these products can be tanked mixed with fungicides, but others cant. If the product is a live agent, such as a bacteria or

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Frost damage to almonds

Almonds are susceptible to frost once they begin to flower. As a flower progresses through bloom (i.e. dormant > pink bud > full bloom > petal fall > small fruit), it becomes more susceptible to cold temperatures. Frost killed flowers/small fruits are easy to identify as the color of the tissue changes. Flowers affected by bloom often have wilted petals or blackened pistils. At petal fall and later, the damage often appears as brown or black tissue within the ovary. This can be identified by cutting the flower/nutlet in half. The photo provides a comparison of flowers affected by frost and a healthy flower. Note the darkened, off-color tissue of the three flowers on the right. All of these have been killed by the frost. Flower sensitivity to cold damage has been studies. Additional information on this can be found here.

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2023 Bloom Considerations

The weather during almond bloom can vary from day-to-day. This creates challenges with farm operations, but also changes how the tree adapts to the weather. Cooler, hotter, or wet weather has significant impacts on the pollination process, fertilization of the ovule, and eventual crop set. Cooler temperatures aren’t necessarily bad for bloom. Flower development is growing degree day based, meaning that cooler temperatures will slow flower development. Additionally, the viability of the ovule and pollen are longer when temperatures are cooler. This natural response increases the pollination period, and partially explains why crop set is often larger than expected during cooler than desired bloom periods. A video presentation on almond pollination and fertilization can be found here. Cooler temperatures, however, do impact honeybee activity. Temperatures below 55F (12C) suppress honeybee activity as more bees are required to remain in the hive to keep it warm. This means fewer bees are available to gather pollen and nectar, affecting the rate of the pollination process. If hive temperatures drop too much, the rate of the queen’s egg laying decreases, affecting eventual hive strength. This could be problematic during extended periods of cold temperatures followed by warm temperatures with a fast/short bloom. The effect of cold temperatures on honeybee activity is why strong hives (8 frames or more) are recommended. Hives with more frames of bees have more bees, which means hive temperatures are higher and more bees can forage. This is often evident on cold mornings, when hive inspections can reveal lower bee activity in weaker hives. If temperatures are too hot, the bloom period can be rapid. In high temperature years, bloom can finish in 7-10 days. High temperatures also shorten the viability of pollen and the ovule. Bee foraging activity must be able to match the rate of flower opening

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Flooding and Almond Tree Survival

When periods of high amounts of rain occur, orchards can become saturated and flooded. During these periods, tree loss may occur, but this is dependent on the duration of soil saturation, the timing of year, and rootstock. Soil saturation reduces the ability for oxygen to infiltrate into the rootzone. Roots require oxygen to respire, and long periods of saturation can lead to root loss by asphyxiation. Fine feeder roots are often the first affected, with larger secondary roots affected during periods of extended saturation or flooding. Tree survival is dependent on how many roots survive and can regrow before periods of high transpiration occur. The sensitivity of almond roots to saturation is dependent on the timing and duration of the flood event. During dormancy, trees are reasonably tolerant due to lower soil temperatures and low rates of respiration. Flood events that are shorter than 7 days will not have any affect on tree performance. Extending beyond this, however, some root loss will occur, and poor spring tree growth may occur. With extended periods – beyond 10 days – tree loss may occur. After the trees have leafed out, the period of tolerance is much shorter. Standing water within an orchard for 5 days will kill mature trees. This is due to the higher activity of the root system due to warmer soil temperatures, and overall tree activity. In these cases, efforts to drain as much water as possible should occur to reduce the impact of the flooding event. If water is moving through an almond orchard, the effect of soil saturation/flooding is reduced. Since moving water carries oxygen, some movement of oxygen into the soil can occur. This will extend the period before negative impacts are seen by several days. For example, an orchard near the Merced River was flooded

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Using Mid-summer Leaf Samples to Guide Fertilizer Decisions: Part 2- Potassium

Potassium fertilizers have seen major increases in price over the past year. This is due to multiple factors, including increased demand, trade embargos with Belarus, and shipping constraints from Russian suppliers. Due to this price increase, many operations are trying to determine the appropriate amount of potassium needed for a specific orchard. Potassium fertility management is different than nitrogen. Potassium moves into the root through diffusion and mass flow. This means that it must be within the active rootzone to be utilized by the tree. Additionally, potassium is a cation (K+) and will respond differently based on the type of soil. High cation exchange capacity (CEC) soils have many charge sites, which can prevent potassium from being available to the plant. This can be further complicated by the presence of micas and other clay minerals. In low CEC soils, the opposite is true, the reduced number of charge sites in the soil mean higher potassium uptake for the plant. However, keep in mind that this higher availability in the soil can also lead to more potassium leaching below the rootzone, increasing costs, or reducing tree productivity. Potassium programs vary. Almonds use a significant amount of potassium, with 92 lbs of K2O needed for every 1000 lbs of kernels produced (92 kg of K2O/metric ton). Potassium is often applied as one of several products, including potassium sulfate, potassium chloride, potassium thiosulfate, and potassium nitrate. These materials may be applied blended with other fertilizers. For example, potassium chloride is commonly used within blends as it is easy to dissolve and stays in solution.  Other sources are available, but are often more expensive and, regardless of the sales pitch, equal in performance. The only exception is compost, which can be cheaper per unit depending on the source and the analysis. Due to the soil

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