The frost event from the week of the February 19th impacted almond production Statewide. Temperatures dropped in many areas below the critical temperatures. This was compounded with a low dew point which made frost mitigation strategies difficult. Damage has been reported from just about all production areas across the State.
Damage reports at this time are challenging to make. Flowers and young nutlets should be checked to see if they have been killed. This is indicated by browning tissue on the inside of the tissues/ovary. This article from 2011 covers a variety of symptoms that may be observed. Damaged flowers and nuts will drop from the tree as the crop begins to set. This may take several weeks and may not be evident until the nuts begin to increase in size. Many will most likely fall off with this upcoming rain storm.
It is a common misconception that the tree will compensate for crop loss with an increase in set percentage of the surviving flowers. This is not exactly true. There is some mild compensation due to a slightly higher set percentage of undamaged buds (~2% or so increase) as well as a gain from increased kernel size due to more energy directed to the embryo during the period of cell division. These two factors, however, are not enough to compensate for flower loss that may have occurred during bloom. Although many often hope, it is unlikely that the late blooming flowers will set as they often lack the energy within localized tissues to form a viable nut.
Once a damage estimate can be made, the season plan should be adjusted. Nitrogen rates should be reduced if losses occurred. Depending on the severity of crop loss, certain pest management practices may also be omitted. These include late season bloom/petal fall sprays and perhaps May or hull-split sprays if the crop load is planned to be not harvested/shook to the ground. Summer sprays to reduce the occurrence of Rust or Alternaria, however, should be made to maintain tree health for the following year. Water demand for the season should also be met in order to further develop the tree and associated fruit bud.
Years like 2018 are challenging, and it is not over yet. Keep an eye on the weather for any future frost events. Hopefully, if these occur, they wont fall below 29F, the critical temperature for the young, developing almonds.
Amini Tareh
April 21, 20211- In our region, the effect of late frost occurs a lot and damages all almond flowers.
What can I do to prevent this problem?
A) Are there any ingredients or fertilizers that I have to give them during winter time?
B) Are there liquid materials for use during the late frost spring?
2. Whenever our trees give us almonds,
Next year we have nothing, which means that next year, all the tree’s flowers fall in early spring.
One year fruit and On year Nothing
What is the reason of this matter?
I appreciated to your kind consideration and help me in above regard
Amini Tareh
David Doll
April 25, 2021Amini,
Hello – sounds like you have a lot of different issues here. First and foremost, are you sure this area is suitable for almonds? Almonds are one of the first Prunus sp. to bloom and therefore has a limited production aea due to frost risk. Secondly – are there any varieties that bloom later than in the spring? This will help reduce the frost risk. There are materials that can help reduce frost damage. These microbials have been shown in apples to provide some level of protection by forming ice which insulates the tree against cold weather. They are un-tested in almonds.
With the alternate bearing, this sound like a varietal, nutritional, or irrigation management issue. Trees, if they bear heavy, will tend to return with less crop due to carbohydrate depletion. This ‘on-year’ can be triggered by the prior year’s frost event – which leads to a large amount of stored energy going into the season. The tree then sets too many almonds, then depleting its reserves, leading to less crop the following year. Good nutrient management – especially potassium – can help reduce this effect, but not eliminate. Good irrigation management practices in the post harvest also help greatly.
Hope this helps,
David