Begin Main Content Area

Black Fly - Sampling and Spray Operations

Field Operations

The Pennsylvania Black Fly Suppression is based on field monitoring and laboratory identifications of black fly populations throughout the Commonwealth. The information gathered as a result of these processes is used by DEP biologists to schedule treatment operations, in coordination with aerial application contractors. DEP biologists are also responsible for reviewing treatment effectiveness.

Larval/Pupal Sampling

  • Prespray samples help determine the need for and timing
    of treatments
  • 15-minute sample taken from riffle/run black fly habitat areas
  • Sample vegetation, debris and rocks, with fingers and forceps
  • Transfer larvae/pupae to vials of 70% ethanol for Lab Identification
  • Postspray Samples help determine treatment effectiveness

Adult Sampling

  • Sampling sites established at parks, schools, ballfields, & other outdoor recreation areas.
  • Disturb vegetation for 100 meters, lay down trail of CO 2 and human scent
  • Take 9 sweeps (3 sets of 3 sweeps) with 10 in. net, shake down adults
  • Transfer adults to labeled sample bottle of 70% ethanol for Lab Identification
  • Collectors are prohibited from smoking or using tobacco products, and may not apply insect repellents during the collection process.

Laboratory Identification

  • Samples delivered to PA DEP Laboratory for identification.
  • DEP biologists and interns identify samples using microscopes and taxonomic keys.
  • Species identifications and counts, as well as life stages, are recorded in GIS-based data system.
  • This information is used in planning and reviewing statewide black fly treatments.

Data System Entry

  • All samples are barcoded for purposes of tracking through the collection/identification process.
  • At the lab, sample and species data is recorded in an internal GIS-based data system.
  • Sample and summary reports, as well as maps, are available in a real-time basis and used in planning and reviewing statewide treatments.

Spray Operations

  • Treatments scheduled only when larval sample results indicate presence of human pest species (i.e.Simulium jenningsi )
  • DEP notifies federal, state, and county authorities, including emergency management personnel, of upcoming black fly treatments.
  • DEP biologists direct treatments in coordination with aerial application contractors.
  • Treatments consist of aerial applications of environmentally-safe, naturally-occurring soil bacteria, Bti .
  • Reviews of treatment-effectiveness after each treatment are conducted by DEP biologists.

Non-Target Biomonitoring

  • Bio-monitoring of aquatic macroinvertebrates and fish is conducted by DEP on selected treatment streams to ensure there are no environmental impacts.
  • Samples collected using US-EPA Rapid Bio-Assessment Protocols at Bti-treatment sites and compared to samples from untreated control sites.
  • Data analyzed using metrics for species richness, diversity, abundance, population density, composition and tolerance.
  • Results confirm that a carefully managed Bti treatment program can provide effective black fly control with no major impacts to non-target organisms.
  • A DEP-funded five-year study by the Academy of Natural Sciences of Philadelphia and Stroud Water Research Center found no significant impacts to fish and insects.

Sampling for Black Flies in a Stream

Black Fly Larvae on Rock


Transferring Adults Net to Bottle


Lab Identification of Black Flies

GIS-Based Data System


Helicopter Spraying to Control Black Fly Populations


Non-Target Biomonitoring