Surviving the Big Freeze?


With the appearance of arctic-like conditions, a number of greenkeepers and groundsmen have been asking if freezing weather in the UK will have a beneficial effect by reducing the levels of insect and nematode pests attacking turfgrass? To answer this question we need to understand the effects of low temperatures on soil invertebrates


By Dr Colin Fleming, the Agri- Food and Biosciences Institute, Belfast


G


enerally, animal and plant species can only survive within a specific


range of temperatures. For example, tropical pests can endure much higher temperatures than pests found in the British Isles, but they will be quickly killed by UK winter conditions. As temperatures drop, invertebrate activity decreases and natural


physiological/biochemical processes start to slow down. If temperatures continue to fall, the animal will cease all activity and eventually die. Our native species are often


exposed to, and therefore must be able to survive, at least short periods of sub-zero temperatures. Extreme low temperatures kill animals by freezing their cell contents and body water, and it is usually the formation of ice crystals inside an animal that will irrevocably damage its cells and body structures, eventually leading to death. In most cases, the longer lasting and more severe the frost, the greater the number of soil invertebrates that will die.


Many invertebrate species adopt the strategy of producing large numbers of offspring, which means that, even if most are killed by extreme weather conditions, small numbers may survive to


establish a new population. Low temperature survival mechanisms are also common in invertebrates. Notably, free- living Antarctic nematodes are able to survive total freezing for most of the year and only become active during the short summer period, feeding in the patches of moss and algae that grow in summer melt-water. The ability of plant parasitic nematodes to survive extreme winter conditions is evident in regions such as North America and Scandinavia, where nematode damage is apparent on golf courses despite exposure to long periods of freezing conditions. Ice nucleators: for water to


freeze, a nucleus of slow moving water molecules must be present. In cold water, ice crystal generation sites can arise spontaneously within clusters of slow moving water molecules or, in some cases, substances that encourage the aggregation of water molecules may stimulate ice crystal formation.


Invertebrates such as nematodes use two main approaches to survive extreme low temperatures. Freezing avoidance - animals prevent ice formation by removing water (dessicating), overwintering in dry sites or by resting in a cocoon or egg. They may also


After death, the female cyst nematode body tans and protects the eggs from extreme environmental conditions


There are over a dozen different types of nematode attacking turfgrass in the British Isles and surprisingly little is known about the effects of freezing on them


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