152 PESTS OF MISCELLANEOUS FIELD CROPS. 



The Mustard Sawfly. 1 



Mustard, rape, cabbage and other cruciferous plants are eaten by 

 the larva of one of the few plant-feeding Hymenoptera known in India. 

 This larva is a black caterpillar-like insect ; it may be distinguished from 

 the true caterpillars by having eight pairs of sucker-feet instead of five ; 

 it is a small insect not more than half an inch long, of a dull black colour ; 

 the skin has the appearance and feel of velvet. 



It is a pest to field cultivation of mustard, rape, etc., as also a more 

 serious enemy to the cabbage and radish crops grown by market 

 gardeners. The larva feeds in the morning and evening, descending to 

 the ground by day. When full fed, it makes a slight covering of silk 

 between two leaves and turns into the pupa, from which the perfect insect 

 emerges in 10 to 12 days. The imago looks like a fly, with a rather short 

 thick-set body marked in black and orange and with two pairs of dark 

 wings. It is a very inconspicuous insect but may be caught in the fields. 



The female lays her eggs singly in the tissue of the margin of the 

 leaf, splitting the edge and depositing an egg inside. There are several 

 broods in the year and the larva continues feeding in the cold weather 

 upon the rabi crops. It is rarely destructive where a large area of 

 cruciferous crop is grown : when it infests small plots or garden cultiva- 

 tion it may cause a large loss. Dusting lime, ashes or soot on the plants 

 has a deterrent effect for market gardens : this is the simplest precaution. 

 Lime or road dust mixed with kerosene is better than ashes. The same 

 applies to field crops ; only small areas are affected and in them a good 

 dusting with any of these mixtures is sufficient to check the pest. The 

 cultivator's practice of collecting the larvae by hand in an earthen pot and 

 carefully liberating them outside the field is of course a useless precaution ; 

 the larvse simply go into the ground and crawl back into the field as soon 

 as it is dark. This insect has been found in widely separated localities in 

 India and is probably of general occurrence. 



The Diamond Back Moth. 2 



In several parts of India crops of cabbage, mustard, radish and similar 

 plants have been attacked by the little green caterpillars of this moth. 

 The leaves have holes in them and present a withered appearance, being in 

 some cases eaten almost completely. The pest is familiar to those who 

 grow these crops, and the cultivators round Surat collect the caterpillars in 

 water and throw them outside the fields. The pest is probably a common 



'54. Atkalia proxima. Kl. (Tenthredinidtc.) 

 2 3. Plutella maculipennis. Curt. (Tineidw.) 



