Aug. 20, I9I7 Cyclamen Mite 377 



NOTES ON SOME OTHER ECONOMIC FORMS 



In the past it has been suspected that mites of the genus Tarsonemus 

 are a frequent cause in promoting diseases in plants. It seems Hkely 

 that many of the diseases to which hothouse plants are subject are due 

 to these mites. The species are so small and so difficult to investigate 

 that very little attention has been paid to them. There are probably 

 many species, but very few have been described, and about these little 

 is known. 



T. floricolus Canestrini and Fanzago (7) has been found on the leaves 

 of a large variety of plants; T. spirijex Marchal (8) has been reported 

 on diseased oat plants; T. chironiae Warburton (11) is mentioned as 

 attacking ferns in England; T. tepidariorum Warburton (11) as attacking 

 a greenhouse plant, Chironia exigera, in England; T. ananas Tryon (10) 

 is reported as a forerunner of a disease of pineapples known as "fruitlet 

 corerot" in Queensland; T. ciilmicolus Renter (9) causes diseases of 

 grasses in Finland, Russia; and T. -waitei Banks (12) is reported to be of 

 economic importance through its destruction of terminal peach buds. 



SPREAD OF THE SPECIES 



The spread of the cyclamen mite is no doubt effected by the ship- 

 ment of seedlings and specimen plants from one place to another. Plants 

 are shipped by growers either as seedlings packed 5 or 10 in a package, 

 with the roots surrounded by moist sphagnum moss, or as specimen 

 or blooming plants shipped in paper pots packed in crates. Plants so 

 packed will travel 7 to 10 days without injury. It often happens that 

 a florist's stock of plants are killed for some reason by fungus or other 

 trouble, or that he is tardy in sowing his seed soon enough to secure 

 plants for the holiday trade, and he is therefore forced to purchase seed- 

 lings or mature plants from some extensive grower. If a wholesale 

 florist is troubled with this mite, he can readily transmit the pest to 

 other localities, either on the plants or in the soil in which they are 

 set, when shipping plants to other florists. Sometimes the plants are 

 not badly infested on leaving the wholesale grower, and no signs of 

 injury are noticed; but a short time after they reach their destination 

 they may become seriously infested, as under favorable conditions the 

 mites multiply very rapidly. 



HOST PLANTS 



T. pallidus does not occur on a great variety of host plants, having 

 apparently thus far confined itself to a few species only. From data on 

 hand it would seem that the mites have a preference for cyclamen, 

 especially the young tender growth of the plants. Next to cyclamen, 

 the mite no doubt prefers the chrysanthemum, and it has also been 

 reported on the snapdragon (A^itirrhinum spp.) in Connecticut and 

 Maryland. Where old cyclamen corms are preserved in the greenhouse, 

 one may find specimens about the corms throughout most of the year. 



