124 INSECT PESTS 



the penalties of introducing an artificial state of things 

 such as obtains in a glass house, and the moist and warm 

 environment is essential to its development. Spraying 

 the plants with hver of sulphur will prevent the spread of 

 the disease, and those plants badly attacked should be 

 pulled up and burnt. The Board of Agriculture has to be 

 notified whenever this fungus appears. (See Plate 27.) 



Another disease of Cucumbers and Melons is Ctrcos'pora 

 melonis, better known as Leaf Blotch. It presents the 

 appearance shown in the sketch, the spots being pale green 

 at first and increasing in size gradually, turning grey and 

 then brown in colour. If these brown spots be examined 

 with a strong magnifying glass, a tiny forest will be seen, 

 where the trees are the minute stalks of the fungus, and 

 the fruit are the spores which drop off when ripe and blow 

 about to carry on their work elsewhere. Why do fungi 

 come in this way and spoil our crops ? It will be found 

 that in most cases it is pale, ill-grown, emaciated plants 

 which are predisposed first of all to get the fungi, and the 

 occurrence of the latter is simply a case where Nature 

 steps in, by her agent, to destroy such plants. What we 

 have to do is to prevent the healthy plants getting 

 infected, mainly by removing all weak stuff, and as a 

 precaution using an emulsion of soft soap and potassium 

 sulphide. (See Plate 28.) 



It has been noticed in the case of cucumber and melon 

 leaf blotch that plants removed to the open air lose the 

 fungus and put out new fohage, thus indicating that the 

 disease has been induced purely by the artificial conditions 

 existing. We should therefore remember that too rapid 

 growth at the expense of robustness is a dangerous course 

 for ourselves and our neighbours. 



Root Knob Eelworm is also hable to attack cucumbers 

 and tomatoes. See remarks at end of chapter on orchard 

 pests. The roots assume the form shown in the sketch, 

 the first symptom being a dropping and withering of the 

 foliage, followed by Hmpness and collapse of the whole 



