April, '21] , DiETz: greenhouse inspection 191 



were replaced by others. Infested plants served as a harbor for scale 

 insects and a source from which plants like ferns, which were often grown 

 in the same house, became infested. When a florist sold a palm or 

 similar plant he often got it back during the winter as a "boarder." 

 Often he took it back in spite of his better judgment and set it am_ong 

 his own plants which he had fought hard to keep clean." In view of these 

 facts should the grower who takes in "boarders," which are generally 

 scale infested, be allowed to ship plants to another grower in another 

 state who does the same thing? Or, if not, to what treatment should 

 lightly infested plants be subjected to kill any infestation of scales or 

 other insects occurring on them? 



Ferns are delicate plants and when they become infested with insects 

 it is practically impossible to "clean them up" without injuring the 

 plants. Hence, what disposition should an inspector make in the case 

 of ferns that show a very slight and scattered infestation of any of such 

 scale insects as the soft scale, the hemispherical scale, or the Boston 

 fern scale ? It is needless to point out that a grower of ferns free from 

 these insects is always afraid of introducing these pests on plants he 

 buys. One florist in a small Indiana city bought several thousand 

 fern plants infested with soft scale from a large grower and distributor 

 in another state. These he unwittingly set among his clean stock with 

 rather disastrous results. How can occurrences like this be best pre- 

 vented ? 



The rapid spread of the chrysanthemimi midge shows what may 

 happen when a serious greenhouse pest becomes established in the 

 greenhouses of one or more large growers. In 1914 it was known only 

 from the houses of one large chrysanthemum grower, but by 1917 eight 

 of the large distributors in widely separated parts of the United States 

 had serious infestations. Fortunately we know now how to control 

 the insect and most of the larger growers in Indiana have it under abso- 

 lute control and several have practically exterminated the pest in their 

 greenhouses. Nevertheless, its spread is continuing. In 1916 when 

 widespread warnings were disseminated many of the smaller growers, 

 such as local florists, became frightened and refused to buy m.um plants 

 for two or three years. But during the spring of 1919 and 1920, lead 

 on by the high price of cut flowers, many florists "plunged" heavily on 

 mums. Even those who bought only such plants as they needed of 

 some new and popular variety often got the midge with them. One 

 large distributor got an infestation in this manner. He fortunately 

 did not buy any chrysanthemum plants from 1914 to 1919 and as a 

 result had no midge. In 1919 he bought 200 plants of a new variety 

 and luckily escaped the pest. But in 1920 he bought 250 plants of a 



