Over the past 20 years, spring frost events have become increasingly destructive to the fruit and berry production in the CEE region. We decided to take a closer look at this risk and briefly describe the current situation with insurance solutions for this risk for horticulture.
Frost can be different
Low temperatures below the critical frost tolerance level are among the most important causes of yield loss in fruit orchards. There are several phenomena of low temperatures, such as frost and freeze.
These terms are often used interchangeably but refer to two different weather events. The term freeze is normally used to describe an invasion of a large, very cold air mass. This event is commonly called an advective or wind-borne freeze. Wind speeds during an advective freeze are usually more than 8 km/h (5 mph) and an additional wind speed of 5 km/h results in an additional temperature drop of 1 degree. Clouds are commonly present during the event and the air is usually quite dry (low dew points). Freeze protection systems are usually of limited value during this type of severe freeze.
A radiational frost, also called a radiational freeze, typically occurs when winds are calm (usually 0 to 5 km/h) and skies are clear. Under such conditions, an inversion (i.e. deviation of temperatures in ground and upper height) may form because of rapid radiational cooling at the surface.
Most people think of frosts as frozen moisture on plant surfaces. However, there are two types of frosts: a hoar or black frost and a white frost. Visible frost (forms small crystals) occurs when atmospheric moisture freezes on plants and other surfaces. Dew (free water) forms when air temperature drops below the dew point temperature. If temperatures continue dropping on cold nights, this dew may freeze (forms frost) by sunrise. When the air temperature is below the freezing point of water, ice crystals rather than dew forms and the frost is called white frost.
The temperature at which this occurs is called the frost point. When the dew point temperature is below the freezing temperature of the air, neither frost nor dew forms. Such a condition is called black frost. The development of frost depends on the dew point or frost point of the air. And the drier the air, the lower the dew point.
Temperature distributions are uneven even on farm level
When it comes to temperatures, not all farming sites are equal, even when located in the same general area. There are numerous factors that can affect minimum temperatures during freeze events.
Chart. Example of different temperature distribution on vineyard. Data source
For example, temperature differences in hilly terrain are quite common on cold nights. As air near the surface is cooled on radiational frost nights, it becomes denser and flows downhill to lower areas where it collects.
Within a given area of a farming region, the most elevated sites tend to be the warmest during freeze events. The trees on northern slopes are much more and severely damaged by the extremely cold and dry winds during advective winter/spring freeze events. Soil characteristics can exert a microclimate effect.
Moreover, the experience has clearly shown that orchards may become active a little earlier in late winter on heavier, clay type soils and/or darker coloured soils (such as reds and blacks) than on lighter coloured, sandy soils. Although the latter tends to warm up faster, but they reflect more heat during the day (trap less heat) and lose it faster during the night.
Human-induced impacts can also be significant. For example, large areas of paved roads, such as interstate highways release substantial heat on cold nights, and this combined with heat released by vehicles and air currents created by traffic, can sometimes provide a beneficial effect to several rows of trees located close to such highways.
Damage to fruit & berry yields, caused by low temperatures
Damage to floral structures may take many forms. Frost on flowers or fruit does not kill the tissue, but it can scar the skin of the fruit and possibly damage the flesh. The internal freezing of tissue of buds, flowers and fruits is what causes serious damage or death of the floral parts. When small floral structures such as flowers or fruits freeze, they may take on several forms of damage. Severe temperatures usually destroy the entire buds, flowers or ovules (immature seed) and ovaries comprising small fruits resulting in rapid abscission of the structure.
Damages from freezes depend on the development stage of the fruit crop. For example, apple trees, during the dormancy period, partial damage of flower buds may be possible, if the air temperature drops to -25 ⁰C, complete damage, if the air temperature drops to -35 ⁰C. The warm December phenomena keeping trees still vegetating creates big trouble for further winter frost tolerance for some types of berries and fruit trees.
Chart. Trend, that witnesses the second half of December is getting warmer and warmer in the South-Eastern part of Poland. Data source: GrECo Group analysis
After resumption of the vegetation temperature at which ground frosts lead to partial damage to apple trees is much higher, e.g. at full blossom stage is -2.9 ⁰C leading to partial loss and -4.7 leading to full loss.
Generally, the crop sensitivity to freezing temperature increases from first bloom to small-fruit stages, and this is when a crop is most likely to be damaged. Sensitivity is also higher when warm weather has preceded a freeze night than if the cold temperatures preceded the freeze.
Insurance against spring frost
Risk prevention measures that lead to the heating of the orchard or vineyard environment (propane heaters, wind machines, irrigation above and below trees, smoke, helicopters, etc.) are sometimes not accessible to farmers in time or do not function properly or fully under certain weather conditions. Therefore, the insurance policy still remains the final frontier to compensate financial outcomes, when frost impact mitigation measures do not work in full.
On the other hand, despite the fact that the government subsidizes crop insurance, such protection tools for fruit and berry crops are not accessible for farmers in many CEE countries. It is explained merely by two main reasons. Firstly, insurers are very cautious about such types of farming, as underwriters and loss adjusters are not well experienced in this area, hence, more focused on more understandable and basic field crops. Secondly, historical big losses and several bad years in a row have made insurance companies to reconsider crop insurance conditions by imposing higher deductibles, increasing insurance rates and bringing stricter underwriting and loss adjustment criterion (e.g. covering only late spring frosts in May).
In our view, stronger public-private partnership in agriculture should be needed, such as, educational horticulture programmes for insurance companies, participation of the government in reinsurance schemes, creating greater product awareness in the market through rural associations, linking with other types of financial support, etc., to regain insurers’ confidence in underwriting this type of risk as a sustainable and profitable business in the long term. In its turn, it will make insurance products more accessible and affordable to the segment of horticulture.
Parametric insurance as an alternative frost risk transfer
The parametric (index) spring frost insurance is an innovative way to financially protect owners of orchards, vineyards and fruit/berry processors against the consequences of bad frost years. In most cases, the parametric policy is offered as the only possible way to cover the risk, which is non-insured by a standard crop insurance policy.
With parametric insurance against frost, the event is insured if the minimum temperature within the risk period is below a certain temperature.
As long as such a minimal temperature condition occurs, the farmer gets the specified amount of insurance indemnity depending on the value of the actual temperature.
Despite advantages of parametric solutions, such as transparency, less paperwork and simplicity of insurance compensations, the insurance market faces the big challenges of basis risk and availability of suitable weather data to insure frosts.
Basis risk in parametric (index) insurance means when the index measurements do not match an individual insured’s actual losses. There are two major sources of basis risk in index insurance. One source of basis risk stems from a poorly designed model and the other from geographical elements.
The good frost parametric model should be based on accurate on-site weather data and consider at least, the fruit/berry development stage and the right frost tolerance parameters for specific types and varieties of crops. Additional factors like windspeed, temperature dewpoint and warm preceding days can be also considered in order to enforce the model. However, regardless of the final perfect model, the basis risk cannot be eliminated.
Frost is a big challenge to the resilience of the horticulture supply chain. There are ways to mitigate partially its impact on yields and compensate financial losses thanks to crop and parametric insurance. On the other hand, a lot of work should be done by professional agricultural insurance experts to design the robust insurance scheme, suitable to the farmer’s and fruit/berry processor’s needs.
Used data sources:
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Group Practice Leader
Food & Agriculture
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