PA-34 instructor pilot reported an near midair collision in the pattern at dto.

Attributes
ACN	1329285
Time
Date	201602
Local Time Of Day	1201-1800
Place
Locale Reference	DTO.Airport
State Reference	TX
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-34-200 Seneca I
Operating Under FAR Part	Part 91
Flight Phase	Landing
Route In Use	Visual Approach
Flight Plan	None
Person 1
Function	Instructor
Qualification	Flight Crew Flight Instructor Flight Crew Commercial Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 300 Flight Crew Total 1100 Flight Crew Type 150
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 500 Vertical 100

Narrative:

We were in the left traffic pattern for runway 36 at dto. This was a training flight in [a] seneca and my student told tower that he had our traffic in sight; but was tracking the wrong plane. We were on left downwind turning base and came within 500 feet of another aircraft on a 2 mile final for runway 36. We turned out to the right and went around to avoid the other aircraft. Our plane was not equipped with TCAS or any traffic advisory system.

Original NASA ASRS Text

Title: PA-34 Instructor Pilot reported an NMAC in the pattern at DTO.

Narrative: We were in the left traffic pattern for runway 36 at DTO. This was a training flight in [a] Seneca and my student told tower that he had our traffic in sight; but was tracking the wrong plane. We were on left downwind turning base and came within 500 feet of another aircraft on a 2 mile final for runway 36. We turned out to the right and went around to avoid the other aircraft. Our plane was not equipped with TCAS or any traffic advisory system.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.