52 



Sofi Rot of the Iris Rliicoiuc 



The soft vol of the iris rliizoinc lias coiitiniu'd to be very de- 

 structive to the bearded iris, a lars^'e nunil)er of i)laiits in the ex- 

 l)ei-iinental field l)eing destroyed duriiio- the t^'rowing season. 'I he 

 (bsease ai)peare(l in early June, liecoming i)articnlarly destructive 

 in late July and .August. Dr. T.. Gordon Utter carried out many 

 cx])erinients during the season with a view to ol)taining i)ossible 

 methods of conti'ol. .As \'et, nn satistactor\- methods of soil treat- 

 ment have been found. Alany \-arieties \\-ere sa\'ed 1)y the ]M'oce- 

 dure of digging them u]) in I'arlv June soon after floNveriug and 

 resetting them in a new area. Dr. Utter has undertaken a sjiecial 

 studv of the cultural characteristics of the l)acterium wliicli causes 

 this disease, and further exjieriments on control will l)e luidertaken. 



Iris Tltrips 



Since 1933, ex])erimcnts in cooperation with the Division of 

 d'ruck Crop and ( Jardcn Insect Investigations. l)ureau ot luUo- 

 molog\- and Plant Ouarantine, Washington, I). C, have been car- 

 ried out for the control of the iris thri])s. an insect ])articularly 

 injurious to the Jajiancse iris. The exj'jeriniental work has been 

 carried on b\' Dr. I.. (}or(lon Utter of the Botanic (iarden and 

 Dr. C. A. W'eigel and Dr. bdoyd V. Smith of the Pmreau of Fjito- 

 niologv. Of ]xarticular interest are the results obtained with the 

 insecticidal tests for the control of the pest. Fumigations with 

 calcium cyanide, carlion bisuliiliide and na])hthalene flakes killed 

 few thri]\s and injiu"ed the iris foliage. X'iciHiue (12.5 ])er cent.) 

 powder fumigation (2 oz. to 1 ()()() cu. ft.) for one hour gave high 

 control with slight foliage injurw Certain sjjrays ])ro\'ed slightly 

 to moderatel}' effective: .Paris (h-een and several arsenate com- 

 ])ounds with brown sugar, thiuram (lisuli)hide, jjhenothiazine, tar- 

 tar emetic-brown sugar, and a commercial extract ot derris root 

 and other substances. Severe iris foliage injiu'}' resulted with 

 the arsenates. Derri.s ])ow(ler ( .0202-. 025 i)er cent, rotenone) 

 with sulphonated castor oil (1-400) or SS (sodium oleyl suli)hate 

 Avith svnthetic resinous base) and 40 i)er cent, nicotine sulj^hate 

 (1-400) with SS or soap Hakes (1-200) as sjireaders gave ')^ to 

 l)ractically 100 i)er cent, thnps reduction. The results usually 

 have been leased on eight weekly pre-flowering applications but 



