David Doll0 commentsApril 25, 2019Nutrient

Fertilizing First Year Almond Trees: Major Nutrients

Determining fertilizer needs for newly planted orchards is challenging. This is due to the desire to grow the trees as rapid as possible while considering the risk of uptake burn and irrigation system inefficiencies. To determine the optimal fertilizer plan, the amount and type of nitrogen and other nutrients need to be considered. Nitrogen: Rate studies conducted in California have found that tree growth seems to peak with 3-4 ounces of nitrogen application per tree. This is based on three different studies – one located near Arbuckle, CA and the other two in Merced County. Within the most recent studies in Merced County, applications were made every three weeks from April through July for a total of six applications. A total of 0, 1, 2, 4, and 6 ounces of actual nitrogen was applied during this period to replicated plots using a NPK blended fertilizer. The source of nitrogen did not create a difference in trunk caliper in the multiple studies within Merced County. Very simply stated, “nitrogen is nitrogen.” There are benefits, however, to the various nutrients that are within fertilizers. If soil levels of phosphorous or potassium are low, utilizing an NPK blend would provide an addition of these major nutrients. The same could be said about calcium-containing fertilizers. If these nutrients are at sufficient levels for plant growth, however, there is minimal benefit from adding additional amounts. Potassium and Phosphorous: Within California conditions, phosphorous (P) and potassium (K) do not appear to be the limiting factor with most soils. The two trial locations within Merced County were located on sandy soil and found no increase in growth from the inclusion of P and K within the fertilizer programs. This does not mean that these major nutrients are not important, rather that many soils contain adequate levels of

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David Doll2 CommentsJanuary 23, 2012Diseases

Pruning Wound Cankers of First Leaf Almond

Figure 1: Fungal infection of a pruning wound that occurred during first leaf pruning on Padre Pruning wound cankers have been observed on all major varieties and are the most damaging to orchards. Cankers that develop on the primary (Figure 1) or secondary scaffolds (figure 2) of young trees will lead to the loss of these scaffolds and eventual tree death. Sometimes infection occurs within the wind cracks found in the base of the scaffolds. Removal of the infected scaffold may be possible, but all of the diseased wood must be removed or the infection will remain. To stave off infection, proper structuring and tying of trees to reduce wind breakage, and pruning when the weather forecast is clear, is advised. Delayed spring pruning or late fall pruning to avoid the rains may be necessary. Pruning cuts should not be cut flush with the tree, but rather be made outside of the branch collar as this increases the rate of healing. The varieties  Aldrich, Carmel, and Padre appear to be more susceptible than Nonpareil or Butte. This disease has been noted to have a high occurrence around rivers, sloughs, and other riparian areas. It is important to note that once the tree is infected, there are no fungicide or nutrient sprays that can cure this disease. Figure 2: Fungal infection of a pruning wound made on a secondary scaffold in Padre. Control strategies for these three diseases have been difficult to develop due to the complexity of the fungi’s lifecycle. Initial infection is thought to occur through airborne spores that move in to an orchard from a residual population. Recent research has shown that uninfected trees can harbor populations of these fungi. It is thought that the fungus has the ability to infect and survive on dead bark, remaining dormant until conducive conditions occur

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Brent Holtz9 CommentsJanuary 17, 2012Horticulture

Plant New Trees High!

Written by Brent Holtz, UCCE San Joaquin CountyOne of the worst things that can happen to young trees from nurseries is that they are planted to deep. Sometimes  they are initially planted at the right height, but then a berm is thrown up around the trees and their crown (the graft union between the scion and rootstock) is covered with the soil from the berm. I saw many diseased trees last spring that had Phytophthora root and crown infections and every one of them had their graft union below the soil line; sometimes the union was more than six inches below. If you are planting or replanting, trees should be planted high on small mounds as shallowly as possible. Planting depth after settling should be no deeper than in the nursery, and the graft union should always be well above the soil line. Try to follow some of these planting tips: 1. Dig a hole deep enough so the roots are spread out and not cramped, 2. Plant the trees so that the nursery soil line is above the current soil line, 3. Plant the highest root a little above the soil line and then cover it with extra dirt, and 4. When planting allow for 3-6 inches of settling in the planting hole. I have never seen trees die from being planted too high, but I have seen many trees killed by being planted too low. This is especially true in heavy soils with a high clay content. These soils have slow water percolation, drain slowly, and remain saturated longer than well drained sandy soils. The mound around the tree trunk forces excess water to drain away from the tree, thus reducing the length of time the crown is exposed to excess surface moisture. Saturated soil conditions can occur

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David Doll4 CommentsApril 20, 2011Diseases

Phytophthora syringae and First leaf Tree Infections

Figure 1: Young almond tree killed by Phytophthora syringae. This year, Phytophthora syringae infections have been quite common. This is most likely due to the long, cool wet spring. Many new orchards have seen 3% or greater infection rate, especially in the variety Nonpareil. Figure 1 shows symptomatology of a tree affected by P. syringae. Leaves on these trees are lesion free, but tend to dry up, becoming crispy. Trees are not always killed, but they may be stunted in comparison to other trees within the orchard.  Examination of the trunk will typically yield amber “gumballs,” which often mark the edge of the fungus canker (Figure 2). When the bark is removed, the canker becomes visible (Figure 3). This disease has been observed frequently, and is commonly referred to as “bundle rot.” Figure 2: Amber colored “gumballs” caused by tree infection with Phytophthora syringae. Although common this year,  infection by P. syringae does not typically cause such a large problem. When temperatures warm above 75F, the fungus within the canker dies, and the affected area heals over as the tree resumes normal growth. Weather this year has been very mild, with few days above 75F. The fungus infects the trees through wounds that occur from digging, processing, delivering, planting, and rough weather. Upon infection, the fungus may remain latent until the tree breaks dormancy. If conditions remain favorable, the fungus continues to grow, eventually killing the tree. Most likely, we do not have a higher amount of this fungus within the orchard in comparison to any other year, but rather that the current cool and wet environmental conditions are promoting fungal growth, causing an increase in observed incidence. Figure 3: Bark removal shows fungal canker of an almond tree affected by Phytophthora syringae. If tree loss or damage occurs within your block due to P. syringae. It is better

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