14 BULLETIN 833, IT. S, DEPARTMENT OF AGRICULTURE. 



larv£e live within the galls alongside the maggots of the gallfly, which they gradually 

 consume. They remain within the galls until mature, when they emerge through small 

 circular holes. This species is the most abundant during the summer months and all 

 of the adults were reared during August. September, and October. In not a few cases 

 as high as 80 per cent to 90 per cent of the maggots were destroyed. 



Tetrasticlms sp. The generic determination of this insect was made by Mr. Harry S. 

 Smith, superintendent of the State insectary, Sacramento, Calif. It is also a small 

 black parasite, somewhat larger than the former and easily distinguished from it by 

 the four-jointed tarsi and other characters. 



EXPERIMENTS IN CONTROL. 



At the outset it must be borne in mind that it is very important 

 that control measures should be closely related to the propagation of 

 the stock, and moreover from the practical and economical point of 

 view these steps should be undertaken at a period in the propagation 

 when the plants can be severely cut back, allowing sufficient time to 

 overcome any injury which may result from such treatment. Inas- 

 much as cuttings are propagated from the stock plants of the previous 

 season, it is evident that the logical time to eradicate an infestation 

 of long standing is immediately after the flowers have been removed. 

 Naturally such precautions as would absolutely safeguard the grower 

 against further spread and increase would have to be inaugurated. 



An experiment conducted in one of the commercial greenhouses in 

 the District of Columbia in which the plants had been heavily infested 

 the previous season was carried out as follows : These heavily infested 

 stock plants were heeled in and pruned back, and the entire portion 

 above ground was thoroughly dusted with a mixture of equal parts 

 of tobacco dust and air-slaked lime as often as the new growth 

 appeared. As a result of such treatment the new growth was kept 

 praoticaliy clean from further infestation and the plants at the same 

 time showed a stimulated growth. The checks which were run simul- 

 taneously had all the new growth badly infested. 



Occasionally it may happen that a grower's previous season's stock 

 was clean and new material or varieties are being received in the form 

 of cuttings or young plants from localities where the insect is known 

 to exist. There is a possibility of introducing the midge on such stock 

 even though no definite signs of the insect are visible. In the spring 

 when cuttings and young plants are being exchanged, an infestation, 

 especially in the egg or very young larval stage, will defy even the 

 most careful and zealous inspectors. Interception made of plants 

 harboring the eggs only can easily be overlooked by virtue of their 

 concealed location in the still unfurled leaf bud. 



A precautionary treatment should be given at the time when the 

 plants or cuttings are taken or received and would prove of inesti- 

 mable value in killing the eggs and immature stages. 



The question of controlling an infestation already in the well- 

 developed gall stage as well as the adult stage must also be con- 



