428 



to this crop in Sumatra, being its chief pest in the south of the island. 

 Its attack is especially severe on rice growing in marshy localities. 

 The wild rice found in such places is probably a food-plant. Though 

 Podops is found in hilly areas, it does little harm there. The younger 

 plants are retarded in growth and their leaves turn yellow, owing to 

 the sucking of the stems. As a rule, measures are useless unless it has 

 been possible to apply them early. The most practical method 

 consists in flooding the rice-field and in sending a number of men 

 through it, disturbing each plant so as to drive the bugs on to the water 

 and into a corner of the field, where they may be collected. The 

 water must be let out immediately afterwards. This procedure may 

 be repeated a few days later. The critical period is when the rice is 

 less than three months old. The above method is impracticable in 

 many cases either from lack of water or from its being impossible to 

 flood the field. In such cases there is no remedy unless natural causes 

 check the infestation. If early attack is followed by a very marked 

 drought of short duration, the bug will disappear, and the plants will 

 not suffer if normal rains then occur. As the bug avoids Hght, an 

 indirect means of combating it would be to adopt more sparse planting 

 allowing of free access to sunshine. The selection of strong varieties 

 of rice with stout stalks is a further protection against this pest. 



PoL.-^K (I. M. W.). Het Greppelwiel (Een vermoedelijke Oplossing 

 van het Emeltenvraagstuk). [The Furrowing Wheel. A Possible 

 Solution of the Problem of destroying Leather-jackets.] — Meded. 

 Landbouwhoogeschool, Wageningen, xxiv, no. 2, 1922, 8 pp., 

 4 plates. (With a Summary in English.) 



The implement described here will, it is hoped, provide a better 

 method for capturing leather- jackets [Tipula] than that of digging 

 trap trenches, as at present practised. It cuts narrow, deep ruts with 

 vertical sides, and by making such ruts about 5-7 ft. apart it is beheved 

 to be possible to "drain " a field of the Tipulids infesting it. An 

 actual test in this respect could not be made owing to a lack of infesta- 

 tion at the time. The apparatus consists of a solid cast metal wheel 

 about 22 in. in diameter and about l^in. thick. This is fixed under- 

 neath a farm cart weighted so as to press the rim of the wheel into 

 the ground to a depth of about 2-| in. The wheel can be raised off 

 the ground by means of a lever. 



Jones (C. R.), Hoerner (J.) & Corkins (C. L.). Methods of combating 

 four Field Crop Pests in Colorado. — Colorado Agric. Coll. Extens. 

 Service, Fort Collins, Series 1, no. 179-A, June 1921, 28 pp., 

 1 plate, 4 figs. [Received 29th June 1922.] 



Loxostege sticticalis, L. (beet webworm) is one of the most 

 destructive pests of sugar-beet, and causes greater loss to the sugar 

 industry in Colorado than any other pest. Its natural enemies include 

 birds and the Hymenopterous parasites, Cremnops vulgaris. Cress., and 

 Mesochorns agilis. Cress, [but cf. R.A.E., A, vii, 10]. Clean cultivation 

 is an important factor in control ; arsenicals are also effective, but 

 depend largely on the time of application, which should be when the 

 larvae are only a few days old. 



L. commixtalis, Wlk. (alfalfa webworm) causes serious injury to 

 lucerne and also attacks sugar-beet. A list is given of nine cultivated 



