94 



MISC. PUBLICATION 6 2 6, U. S. DEPT. OF AGRICULTURE 



YUCCA 

 Yucca Plant Bug 



The foliage of yucca, or Adam's 

 needle, is rendered yellowish and sick- 

 looking from the sucking of the plant 

 juices by the yucca plant bug known 

 scientifically as Halticotoma valida Reut. 

 The bugs stipple the leaves and cover 

 them with numerous black specks of 

 excrement, which imparts an unsightly 

 appearance. This insect is also recorded 

 as feeding on cactus. It usually makes 

 its appearance early in May and may be 

 present until frost. The adult, which 

 is about V% inch long, is a stout-looking 

 bluish-black bug with head and waist 

 reddish brown. It does not fly readily, 

 but it runs to the other side of the leaf 

 or stem or down to the base when dis- 

 turbed, and is difficult to catch. The 

 vounger stages are bright scarlet. 

 They are often so numerous that the 

 leaves are teeming with them. This 

 insect has been known for a long time in 

 Texas, Arizona, and New Mexico, but 

 in recent years it has been frequently 

 found from Washington, D. C, south- 

 ward. Little is known about its devel- 

 opment and habits. 



Treatment. — Spray with nicotine 

 sulfate or pvrethrum. 



Prevention. — Removing and burn- 

 ing all dead and sickly plant parts late 

 in the fall mav be of value. 



Other Pests of Yucca 



Page 



Red spiders 11 



Flower thrips 74 



Stalk borer 34 



ZINNIA 



Four-Lined Plant Bug 



The four-lined plant bug (Poecilocap- 

 sns lineatus (F.)) feeds by sucking the 

 juices from the leaves and tender growth 

 of many flowering plants and shrubs. 

 Aster, chrysanthemum, coreopsis, cur- 

 rant, dahlia, goldenglow, heliotrope, 

 peony, phlox, rose, snapdragon, sun- 

 flower, sweet pea, and zinnia are among 

 the many plants attacked. The feeding- 

 causes small sunken areas on the upper 

 leaf surfaces which appear somewhat 

 like fungus disease spots (fig. 159). 

 In heavy infestations the leaves soon 

 turn brown and drop. The adults, 

 which are about % to % inch long, are 

 similar in shape to the tarnished plant 

 bug (fig. 57, p. 35), but are greenish 

 yellow with four distinct black stripes 

 down the back or wing covers. The 

 nymphs are bright red to orange. There 

 is only one generation annually. The 



:.*&£ 



Figure 159. — A, Leaf showing spots 

 caused by the feeding of the four-lined 

 plant bug; P, uninjured leaf. 



females lay the overwintering eggs in 

 the fall in tender stems of currant and 

 other shrubby plants. The tips of the 

 whitish eggs are left protruding and 

 may be detected on careful examination. 



Treatment. — Because of their ex- 

 treme activity the adults are difficult to 

 control. Spraying in May or June, 

 while the nymphs are present and before 

 the adults develop, using a strong solu- 

 tion of nicotine sulfate, pvrethrum, or 

 derris, with a good wetting agent, is 

 recommended. Dusting with these ma- 

 terials may be used in place of spraying. 



Prevention. — Remove and burn all 

 plant remains, and especially any plant 

 stems on which overwintering eggs are 

 detected. 



Other Pests of Zinnia 



Page 



Stalk borer 34 



Spotted cucumber beetle 7 



Blister beetles 7 



Japanese beetle 48 



Asiatic garden beetle 21 



Tarnished plant bug 35 



Aphids 9 



Red spiders 11 



Morning-glory leaf cutter 59 



Leafhoppers 10 



Flea beetles 8 



INSECTICIDES 



Chemicals in various forms are em- 

 ployed in controlling insects, mites, and 

 related pests. These chemicals, or in- 

 secticides, are usually applied in the 

 form of dusts, sprays, or fumigants. 

 Since insects, generally speaking, are 

 provided with either chewing or sucking 

 mouth parts, two classes of insecticides, 

 stomach poisons and contact insecti- 

 cides, are used to combat them. 



When insects of the chewing type, 

 such as leaf-eating beetles and cater- 

 pillars, are infesting plants, a stomach 

 poison, such as one of the arsenicals or 

 one of the fluorine compounds, may be 

 used. These insecticides are applied to 



