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. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture -- Massachusetts. 24 MASS. EXPERIMENT STATION BULLETIN 318 A similar field planted on the same day but located next to set onions showed an infestation of 35 thrips per plant by July 7. By July 14 the plants were becom- ing 1 adly scored. The maximum infestation was reached on July 28 with an average of more than 80 thrips per plant. At that time the damage was so severe that the field was sprayed in the hope of securing at least a partial crop. The plants in this field were badly scarred and stunted. Their maximum growth
. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture -- Massachusetts. 24 MASS. EXPERIMENT STATION BULLETIN 318 A similar field planted on the same day but located next to set onions showed an infestation of 35 thrips per plant by July 7. By July 14 the plants were becom- ing 1 adly scored. The maximum infestation was reached on July 28 with an average of more than 80 thrips per plant. At that time the damage was so severe that the field was sprayed in the hope of securing at least a partial crop. The plants in this field were badly scarred and stunted. Their maximum growth amounted to little more than half that of the plants in the field isolated from sets and they matured a light crop of inferior-sized onions. Susceptibility of Different Varieties and Types of Onions to Thrips Attack It has been recognized for soma years that extreme differences exist in sus- ceptibility of different varieties of plants to insect injury. During the past year investigations of this phase of onion thrips control carried on in Massachusetts were of two types: (1) a comparative study of six varieties—Ohio Yellow Globe, Ebenezer, Harris No. 58, Utah Experiment Station Sweet Spanish, Harris No. 597 Riverside Sweet Spanish, and Winegar Strain Sweet Spanish—in their resis- tance to thrips attack, and (2) a similar study of different strains of Danvers Yellow Globe, the standard variety now being grown in the Connecticut Valley. The different varieties were all planted the same day and were so located that they had equal opportunities for thrips infestation. Weekly counts were made of thrips abundance throughout the season. The observations are presented in the accompanying chart. CoMPftRFIT IVE SuSCEPT IBI LITY or Different Varieties of Onions toThrips Attach CBCHCZTR h*»b<s sa HARRIS i"9 7 \JTHH EYPrRiriCNT STftTIO WINrGfiR STRHIN. From these data it will be observed thai the infestation on the two varieties, Utah Experiment Station and Winegar Sweet Spani
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