NAPHTHALENE AS A GREENHOUSE FUMIGANT 19 



The greenhouse thrips 1 and the onion thrips 2 are very effectively controlled, 

 and usually with less exposure than is necessary to kill the red spider. Com- 

 plete control is not always obtained, however, because many thrips hide in the 

 unopened buds where they are partially protected from the fumes. The glad- 

 iolus thrips 3 is controlled by naphthalene fumigation; but the gladiolus, 

 especially when forced in the greenhouse, may be slightly injured, and the 

 treatment is therefore not recommended. 



The green chrysanthemum aphid, 4 the black chrysanthemum aphid, 5 the 

 green peach aphid, 6 and the bean aphid, 7 the last two being frequently found 

 on carnation, have been completely controlled by two or more fumigations, and 

 it is probable that the treatment is equally effective against all species of aphids 

 likely to be present in the greenhouse. However, one fumigation with naph- 

 thalene is not so effective against aphids as one fumigation with nicotine or 

 hydrocyanic acid gas, and the value of naphthalene for this purpose is prin- 

 cipally to control aphids when it is being used to combat other pests. 



Adult white flies 8 are killed to about the same extent that aphids are killed; 

 but as is the case when nicotine fumes or hydrocyanic acid gas are used to 

 combat this pest, the majority of the larvae and pupae survive, and repeated 

 treatments or spraying in addition to fumigating may be necessary to give 

 practical control. 



The citrus mealy bug 9 is killed in large numbers by successive fumigations 

 with naphthalene and frequently the soil under heavily infested plants will 

 be covered with their bodies after treatment. However, ten fumigations have 

 not entirely freed the plants of these pests, and the treatment cannot be recom- 

 mended as a practical control measure. 



All stages of the cyclamen mite 10 are resistant to naphthalene fumigation. 

 Furthermore, it is the habit of these pests to live within the unopened buds of 

 flowers and leaves, even working deeply into the crown where they are protected 

 from sprays and fumigants. Frequent fumigations at intervals of 5 to 7 days 

 reduce injury by this pest but will not give complete control. The broad 

 mite, 11 a closely related species which is frequently found on the same plants, 

 lives on the exposed surfaces of the leaf and is more effectively controlled by 

 naphthalene fumigation. Smith (18) found that the eggs of this mite are very 

 resistant to this treatment, but by repeating fumigations at least three times 

 at intervals of 5 to 7 days to kill the active stages, this mite was quite satis- 

 factorily controlled. 



Bulb mites 12 when exposed to two strong fumigations became sluggish but 

 revived in 24 hours, and mites which were in the soil or in cavities in decayed 

 bulbs were unaffected. In no case did the fumigant penetrate the soil sufficiently 

 to control soil-inhabiting animals. Sowbugs, centipedes, and millipedes are 

 frequently killed when exposed to naphthalene, but large numbers of them are 

 usually sufficiently protected in their hiding places to survive fumigations. 



The moths of the greenhouse leaf tyer, 13 the rose leaf roller, 14 and cutworm 

 species, 15 have been killed by naphthalene fumigation, but the larvae of these 



1 Thrips tabaci L. ^Pseudococcus citri Risso 



2 Heliolhrips haemorrhoidalis Bouche lOTarsonemus pallidum Banks 



3 Taeniothrips gladioli M. S. ll Tarsonemus latus Banks 



^Colorodoa rufomaculata Wilson MRhyzoglyphus hyacinthi Boisd. 



i Macrosiphon^ella sanborni Gillette ^Phlyctaenia rubigalis Guen. 



*Myzus persicae Sulz. u Cacoecia rosaceana Harris 



''Aphis rumicis L 15 Family Noctuidae 

 s Trialeurodes vaporariorum Westwood 



