David Doll4 CommentsAugust 20, 2019Diseases

Almond Shaker Damage

Shaker damage is commonly observed across orchard operations. This damage occurs when the force of the shaker is greater than the strength of the bark, causing it to tear away from the tree. The obvious damage not only impacts tree vigor, but also provides an opportunity for infection by wood canker fungi which can kill the tree. If the shake is properly timed and executed, shaker damage can be greatly reduced (and even eliminated) within an orchard. A common misconception is that trees that are kept too wet during the harvest period will be damaged by the harvesting process. Interestingly, this has never been supported in research nor found to be consistently true across operations. Research in the mid 90’s by Gurusinghe and Shackel found that withholding irrigation during July through harvest did not reduce bark damage of the trees. To further elaborate, they found no difference in bark strength with respect to shaker damage for almond trees grown under various irrigation treatments. Irrigation treatments included a wet treatment and dry treatment, in which mid-day stem water potential (SWP) was maintained at -9 bar and -20 bar, respectively, through the month of July/August. Despite this range in tree water status, both treatments exhibited the same gradual increase in bark strength through July and August. Based on this, the researchers concluded that water stress did not influence the timing or rate of tree bark strengthening. Based on the lack of direct effect of moisture status on tree bark strength, it is thought that the damage observed in wet areas of the orchards is most likely due to the delays in ripening. Research has found that decreased water stress (Goldhamer and colleagues, 2006) and high nitrogen status (Saa and colleagues, 2016) both  delay ripening. These trees, when shaken at the same time

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David Doll0 commentsAugust 11, 2009Horticulture

Preparing for Harvest

It looks as if harvesting will be underway for Merced County within the next week to 10 days, with the date occurring earlier for growers on the West and South Sides of the county. With harvest, there are many preparations that must be taken into consideration. Water Management:In order to determine the last pre-harvest irrigation, a target harvest date must be set. Approximately two weeks after the last irrigation are required to “dry down” the trees enough to minimize bark damage from shaking. This time period does vary upon soil textures, with sand and clay requiring less and more time, respectively. This depletion of soil moisture tightens the bark to the trunk and prevents damage from the shaker attachment. Also, as the season progresses, the bark adheres tighter to the trunk. Therefore, with an earlier harvest, the chances of shaker damage are increased. In soils of low water holding capacity (i.e. sand) it may be necessary to irrigate between the harvesting of the varieties. Proper water management between varieties is just as critical as water management before harvest because during this period the tree is developing the fruit bud for the coming season. Any moderate to severe water stress during this period will reduce the formation of fruit bud. Timing of Harvest:Harvest timing should be considered using the following criteria: – The need to avoid naval orange worm damage to nuts on the tree and ant damage once nuts are on the ground; – The ability to achieve maximal nut removal; – The ability to maintain yield and quantity; – Minimization of tree injury; – Availability of harvest equipment; – weather conditions that may cause crop loss or damage (i.e. rain). A few of these points are highlighted below: Damage caused by Navel Orange Worm and Ants:Early harvest prevents the

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David Doll0 commentsJune 4, 2009Diseases

Ceratocystis of Almond

Ceratocystis or “mallet wound canker” has been found on almond throughout California for almost 50 years. This fungal canker, caused by Ceratocystis fimbriata, can develop on areas of the trunk or branches that have been damaged by tractors, hedgers, and harvesting equipment. Pruning wounds are also susceptible. Cultivars that are most susceptible include Nonpareil, Mission, and Ne Plus Ultra. Ceratocystis cankers appear as either water soaked or dry cankers. Amber-colored gum is found at the canker margins. Infected tissue turns brown and the area eventually becomes sunken. Unlike Phytophthora infections, Ceratocystis remains active during the summer months in which rapid canker growth can occur. Cankers can girdle limbs, scaffolds, and tree trunks.Limbs 4-6 inches in diameter have been observed to be girdled in 3-4 years, while smaller branches are killed more quickly. Ceratocystis cankers appear as either water soaked or dry cankers. Amber-colored gum is found at the canker margins. Infected tissue turns brown and the area eventually becomes sunken. Unlike Phytophthora infections, Ceratocystis remains active during the summer months in which rapid canker growth can occur. Cankers can girdle limbs, scaffolds, and tree trunks.Limbs 4-6 inches in diameter have been observed to be girdled in 3-4 years, while smaller branches are killed more quickly. Several species of sap-feeding beetles and fruit flies spread Ceratocystis. These insects feed on the fungus, ingesting and coming into bodily contact with the spores. The spores are then transported to other trees and deposited on the bark by the insects. Rains and sprinkler irrigations can wash the spores into fresh pruning wounds or other injuries. Once the fungus infects the cambium, it will begin to invade the healthy bark and xylem tissues of the tree. Dark stains may permeate into the heartwood of the tree, but rarely is the fungus found in these tissues.

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