April, '21] DiETZ: greenhouse inspection 189 



It is necessary here to point out that there is a very important dif- 

 ference between greenhouse grown plants and nursery stock at the time 

 each is distributed. Nursery stock is dormant when shipped. The 

 leaves are off and practically all soil is removed from the roots. There 

 are some exceptions as in the case of conifers and other evergreen plants. 

 On the other hand plants grown under glass are generally shipped in a 

 growing condition. Except in the case of cuttings and bud-wood, 

 defoliation is out of the question and so is the removal of soil from the 

 roots. Therefore, any insect or disease attacking the leaves, stems, or 

 roots, are generally carried with the plants. 



The first problem is, "What shall we regard as 'clean' plants?" — in 

 other words, "What are plants free from dangerously injurious insects 

 and plant diseases?" The following list of greenhouse insects (including 

 mites) and plant diseases has been arranged in accordance with the 

 prevalence of the pests in Indiana greenhouses (See p. 190). 



It is evident that many of the tropical and sub-tropical insects, such 

 as the mealy-bugs and scale insects listed, are serious pests in California 

 and Florida and along the Gulf of Mexico ; therefore, their very presence 

 in a greenhouse ought to be sufficient grounds for refusing the grower a 

 permit to ship plants to the regions mentioned. The terminal inspec- 

 tion systems in use in California and Florida will prevent infested stock 

 from entering these states. Yet, should the presence of these pests 

 warrant the refusal of a permit to ship when the plants are grown for 

 northern distribution only, and where perhaps the only persons who will 

 have trouble with them will be florists and their patrons? This distribu- 

 tion of, in most cases lightly infested, plants from florist to florist and 

 from florist to patron has lead to some interesting results. Ten years 

 ago the coleus was one of the most popular bedding plants in Indiana, 

 But today that popularity has decreased so far that few florists grow 

 this plant, and all this is due to mealy-bugs. The florists could not, 

 or did not, keep these plants free from the pest with the result that when 

 the plants were bedded out with others during the simimer it was only 

 a matter of time until the other plants, as well as the coleus, were infested 

 and the bed ruined. The patrons of the florist have learned that the 

 coleus is a plant not to buy because of the danger of their being infested 

 with mealy-bugs. 



Many Indiana florists have also discontinued the growing of palms 

 and other subtroj^ical jjlants used for decorative purposes because of the 

 difficulty they have had in con trcl ling the tropical and subtropical scale 

 insects attacking them.. Ten years ago a greenhouse was incomplete 

 without a stock of palm.s and other tropical decorative plants. Such 

 plants usually went from bad to worse year by year and as they died 



