GENERAL PRA CTICE. ENEMIES. 



2 7.5 



often be seen a globule of blackish fluid, which, being deposited from time to time, stops 

 up the pores of the leaves. 



Thrips feed upon leaves and tender shoots, and also attack fruit, causing the parts 

 infested to become paler in colour, and often to wither. Under glass they are most 

 prevalent in summer and autumn ; but where plants are grown in fruit houses, and the 

 temperature and atmospheric conditions suitable, they are seldom inactive. 



Yellow thrips occasionally make their appearance on vines, and infest the ripe fruit 

 of plums, peaches, and nectarines, rendering those as well as grapes disgusting. It (Helio- 

 thrips ochraceus) has black eyes and a 

 hairy body. This, happily, is uncom- 

 mon. Not so, however, is our native 

 very small black or dark coloured thrips 

 (Heliothrips vulgatissima), which as 

 early as April is common in the flowers 

 of fruit trees, crawling about the in- 

 terior, the corolla, stamens, and all 

 parts receiving attention. This species 

 does not appear to injure the trees, yet 

 impairs the blossoms, which seldom set 

 well. Fortunately thrips are rarely 

 hurtful to fruit trees outdoors, though 

 in a dry season they are sometimes 

 troublesome, yet they yield readily to 

 forcible syringing, and the washes ad- 

 vised for aphides. 



Prevention under glass must be 

 directed to cleanliness. Washing the 

 infested vines or trees with soapy water in summer, and cleansing the house, after the 

 infested trees are leafless, must not be neglected. Every care must be taken not to 

 introduce thrip-infested plants into fruit houses, and the trees must be kept healthy by 

 due attention to ventilation, and abundance of moisture both in the air and soil. Forcible 

 syringing with clear water expels thrips, and where this can be practised, and proper 

 culture is provided, they ought not to appear. 



Fumigation with tobacco is a good remedy, having the foliage dry, and the smoke 



x x 2 



Fig. 82. THRIPS (HELIOTHRIPS ILEMORRHOIDALIS) ON 

 VINE LEAF, SHOOT, AND BUNCH OF GRAPES. 



Upper surface of vine leaf showing : thrips seated near 

 veins long black marks ; excreta black dots ; extent of 

 injury to tissues white patches; damage to leafstalk 

 (petiole) whitened appearance ; injury to wood and grapes 

 white parts infested. Three figures to left beneath the leaf 

 larvae ; winged insect under the grapes perfect thrips 

 all greatly magnified. 



