A moisture responsive device is described having a moisture responsive elementcomprising at least a moisture responsive formation of a first material in associationwith a less moisture responsive formation of a second material, in that the firstmaterial has a greater tendency to absorb moisture and to increase in volume asa result than the second material, the two formations being so mechanically arrangedtogether that such swelling tends to cause mechanical deformation of the moistureresponsive element and an actuation member optionally of flexibly resilientmaterial in mechanical association with the moisture responsive element sothat distortion of the moisture responsive element in the presence of moisturetends to mechanically distort the actuation member and thereby cause the actuationmember to change between at least a first functional state and a second functionalstate. A method of use, especially in irrigation control, is also described.
