28 



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



Mexican Mealybug 



Although other species of mealybugs 

 occur on chrysanthemum, the Mexican 

 mealybug (Phenacoccus gossypii Towns, 

 and Ckll.) is the most serious pest. 

 This species will also feed on and injure 

 other garden plants, including coleus, 

 gerbera, fuchsia, bouvardia, and calen- 

 dula. It attacks the leaves, stems (fig. 

 44), and flowers in all stages of growth. 



Figure 44. — Mexican mealybugs clus- 

 tered on a chrysanthemum stem. 

 Slightly enlarged. 



On chrysanthemum especially it causes 

 a stunting and distortion of the leaves; 

 otherwise the injury, habits, and ap- 

 pearance are similar to those described 

 under Coleus, on page 31. The adult 

 female is light bluish gray and about l /% 

 inch long. A female may deposit an 



average of about 400 eggs, and these are 

 laid in cottony sacs. Plants obtained 

 from infested nurseries or greenhouses 

 are responsible for infestations. This 

 insect does not survive the winter in the 

 Northern States. 



Treatment. — Apply a thiocyanate 

 spray (p. 102) at intervals of a week or 

 10 days. It is advisable to syringe the 

 plants with water within a few hours 

 after spraying, to avoid spray injury. 

 The treatments recommended for other 

 mealybugs (p. 31) may be of some 

 value, but are less effective against this 

 species. 



Prevention. — Carefully examine all 

 new plants before they are set out in 

 the garden. If found infested, treat 

 them with the above-mentioned spray, 

 or, if badly infested, destroy the plants. 



Chrysanthemum Lacebug 



The chrysanthemum lacebug (Cory- 

 thucha mar?norata (Uhl.)) may at times 

 inflict considerable damage to the foliage 

 and stems of chrysanthemums by suck- 

 ing the sap. The adult, similar to the 

 one shown in figure 45, is less than % 

 inch long and is easily recognized by its 

 lacelike wings and lacy hood over the 

 head. The nymphs, or young, are wing- 

 less and have spines on the body. They 

 leave tiny, dark, resinous spots of ex- 

 creta on the under sides of the areas fed 

 upon (fig. 46). This lacebug breeds on 

 many weeds and is often found on 

 goldenrod, from which it migrates to 

 chrysanthemum, aster, scabiosa, and 

 other garden flowers. When present in 

 large numbers it quickly ruins the 

 plants. There are several generations 

 annually. 



Treatment. — Spray or dust the 

 under sides of the leaves with nicotine 

 or pyrethrum. 



Figure 45. — Adult of the sycamore 

 lacebug. Eight times natural size. 



