the container means so that the device can be sealed on the plant material to release the gas through the layer applying the container means to the plant material so that the gas is released wherein the development of the plant material is affected fig1 to 4 show a patch 10 which is applied to the surface or skin of a fruit or vegetable such as skin 101 of banana 100 the device includes an outer shell 11 with a domed portion 11a the shell 11 is closed by a gas permeable polymer sheet 12 having an adhesive strip 13 around the periphery as shown in fig4 the margin between and around the shell 11 and sheet 12 is sealed as by heat sealing the shell 11 and sheet 12 form a chamber or space 14 wherein a gas can be released upon demand through the permeable sheet 12 to the fruit or vegetable crystals of 2 chloroethyl phosphonic acid ethrel 18 are applied with an adhesive such as contact cement to sheet 12 space 14 contains a relatively unreactive dry gas such as air oxygen nitrogen which does not affect the development of the fruit or vegetable affixed to the inside of the shell 11 inside the space 14 is a button 15 including a cover 16 which is secured and is sealed to the shell 11 the button 15 confines aqueous gel 17 having a high ph preferably between about ph 7.