8 THE GREENHOUSE THRIPS. 



FOOD PLANTS. 



The greenhouse thrips feeds on a large number of ornamental 

 plants. In this country it has been recorded as feeding on liliaceous 

 plants, azalea, PeUea liastata, aspidium, croton, dahha, phlox, ver- 

 bena, pink, ferns, vines, cherry laurel (Prunus caroliniana), laures- 

 tina, palms, Ficus, and fuchsia. In California it lias been found on 

 raspberry, guava (Psidium guajavd), and orange. Tliis thrips 

 damages the mango (Mangifera indica), alligator pear (Persea gra- 

 tissima), and maple in Florida, and has been recorded from St. Vin- 

 cent and the Barbados on cacao (TJieohroma cacao), kola, and the date 

 palm (Phoemx dactylifera) . In Europe this thrips has been recorded 

 as preying upon aerides, azalea, begonia, camarotes, cattleya, crinums, 

 dendrobium, eucharis, Ficus, grape, laeha, lefortia, marcintacia, 

 pancratium, phalenopsis, banana, and viburnum. In Australia it is 

 recorded as occurring on different species of eucalyptus. 



REMEDIES. 



For the treatment of this pest there are a number of good remedies. 

 The question as to the best method to employ depends upon the size 

 of the greenhouse infested and upon the experience of the person 

 engaged in treating the insect. 



Fumigation with nicotine 'papers. — Any of the standard fumigating 

 papers will give good results against tliis pest if they are strictly fresh 

 and kept tightly sealed. Fumigation should be done at night in a 

 moist atmosphere, and the papers should be used at the rate of about 

 2 sheets for every 1,000 cubic feet of space. Early in the morning 

 the house should be opened and thorougldy aired. 



Fumigation with nicotine liquid extracts. — Lic[uid extracts of nico- 

 tine offer one of the best methods of greenhouse fumigation and 

 against tliis pest are very successful. Those made up of 40 per cent 

 nicotme should be used at the rate of 1 ounce to every 1,000 cubic 

 feet of space and the weaker solutions at greater strengths. The 

 preparation should be evaporated over small lamps or stoves, and 

 to prevent scorching should be diluted with water, approximately 

 two-tliirds. Fumigation should be carried on at night in a moist 

 atmosphere, and the greenhouse should remain closed all night. 



Fumigation with hydrocyanic-acid gas.^ — When fumigating with 

 hydi'ocyanic-acid gas great care should be taken, as tliis gas is fatal 

 to all animal life. The work must be conducted at night, and the 

 plants should have dry foliage. In treating this insect, use from 0.01 

 to 0.05 gram of potassium cyanid per cubic foot for from two hours 

 to all night, the strength and length of exposure varying according 

 to the tightness of the house and the kind of plants that are being 



1 For complete directions for the use of hydrocyanic-acid gas, see Cirs. 37 and 57, Bur. Ent., U. S. Dept. Agr. 



