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When to Apply Insecticides 
Dahlias require insecticidal protection from the European corn 
borer during a period of 30 days or more, beginning late in July or 
early in August. A spray or a dust treatment should be applied im- 
mediately when signs of infestation have been found* such as hatching 
of corn borer egg masses or injuries in terminal buds as described on 
pages 2 and 3* Applications must be repeated thereafter at 5-day 
intervals, owing to the constant production of new and unprotected 
bud growth, the continuous hatching of corn borer eggs, and the dilu- 
tion of insecticidal residues caused by rainfall. Tor example, if 
hatching or infestation was first observed and an insecticide applied 
on July 25 » the succeeding applications would be scheduled for July 30 » 
and August 4, 9, and Ik, and continued into the first week of September 
according to the occurrence of corn borer hatching. Somewhat less 
satisfactory control may be expected when treatments are applied at 
weekly intervals. If insecticide applications are delayed until a 
week or two after initial infestation, these treatments should provide 
protection for the late blooms, but earlier infestation of stalks and 
branches is likely to cause breakage. On the other hand, blooms 
become infested when insecticide applications are discontinued too 
soon* 
SUPPLEMENTARY CONTROL MEASURES 
Disbudding and Disbranching 
An understanding of how borers get into dahlias suggests several 
methods that may be adopted for keeping them out. Signs of infestation 
in shoots and buds, for example, indicate where pruning will prevent 
further trouble, and removal of infested shoots and buds is sometimes 
sufficient in gardens that are tbij lightly infested. However, the 
corn borer does not always enter those lateral shoots and flower buds 
that would normally be removed by good pruning practice. Where 
heavier infestation prevails, disbudding and disbranching cannot be 
depended upon to protect the plants from serious injuries or the loss 
of quality blooms. 
Use of a Tent 
Choice varieties are sometimes grown under complete tents con- 
structed of tobacco shade-cloth, and this practice has been found to 
reduce infestation greatly. Occasional injury is caused by larvae 
hatching on nearby plants and gaining access te those grown under the 
tent, or by larvae hatching from 9gg masses laid upon the tent, from 
which the larvae penetrate the screen and drop or crawl to plants 
within the enclosure. In localities where moisture held inside such a 
tent does not promote tenderness in the blooms or fungous disease in 
the plants, this has been found to be a very satisfactory method of 
keeping borers out of dahlias. 
