Environmental Leadership
Saving the Hemlocks, one beetle at a time.
Predator Beetles
Upon importation all beetles were closely studied under quarantine conditions until USDA approval as use as a biological control for the hemlock woolly adelgid.
Sasajiscymnus tsugae (St)
Sasajiscymnus tsugae lifecycle in the southern U.S.
Number: 1276006Description: egg inserted in budscale
Photographer: Carole Cheah, Connecticut Agricultural Experiment Station
a small black beetle, about 2mm long, and is compared to a poppy seed. This beetle, which belongs to the family Coccinellidae, has been imported from Japan since the 1990's. It feeds primarily on adelgids and both larvae and adults feed on all stages of the hemlock woolly adelgid.
Number: 1276007Description: Larva
Photographer: Carole Cheah, Connecticut Agricultural Experiment Station
St is active during the spring and summer and hibernates in the winter. They have two generations a year, just like HWA, and can produce up to 500 eggs in their lifetime.
Number: 1276006Description: egg inserted in budscale
Photographer: Carole Cheah, Connecticut Agricultural Experiment Station
At optimal conditions the beetles can hatch from an egg in 8 days, and spend around 25 days in the larval stage before it pupates into an adult. The adults are then sexually mature around 3 weeks after pupation.
Number: 1276008
Description: Pupa
Photographer: Carole Cheah, Connecticut Agricultural Experiment Station
There are 3 Scymnus species being worked with as control options for the hemlock woolly adelgid. They have been imported from various regions of China since 1996. Like the St beetles they belong to the Coccinellid family and are a small black beetle, with coppery colored elytra (hard wings). Some species have two black dots on their elytra as well. They prefer to feed on adelgids, but will feeds on aphids to a certain degree. The Scymnus beetles are more active during the spring and summer and newly matured adults typically overwinter one season before laying eggs. Unlike the St beetles they have one generation a year, and can lay up to 200 eggs.
Number: 1276010Description: Scymnus camptodromus Yu and Liu adults
Photographer: Guangwu Li, Chinese Academy of Forestry
Number: 1276011Description: Scymnus sinuanodulus Yu and Yao adults
Photographer: Guangwu Li, Chinese Academy of Forestry
S. sinuanodulus has a native range that is similar to that of the southern Appalachians.
Number: 1276012Description: Scymnus ningshanensis Yu and Yao adults
Photographer: Guangwu Li, Chinese Academy of Forestry
Number: 1276013Description: Egg inserted into budscale
Photographer: Lynn Jones and Nathan Havill, USDA Forest Service
The eggs of S. sinuanodulus and S. ningshanensis hatch in about 10 days; the eggs of S. camptodromus enter diapause and do not hatch until the following spring.
Number: 1276014Description: Larva
Photographer: Lynn Jones and Nathan Havill, USDA Forest Service
Both larvae and adults feed on all stages of HWA, however, the 1st instars mortality rate is high if they don't have adelgid eggs or 1st instar crawlers to feed upon.
Number:1276015Description:Pupa, Masked with defensive secretion at tip of setae
Photographer:Lynn Jones and Nathan Havill, USDA Forest Service
All three beetles pass quickly through four larval instars and a pupal stage (Lu et al. 2002), with total development time from egg hatch to adult between 25 and 30 days at room temperature, 20°C (68°F) (Wang et al. 2000, Montgomery et al. 2002).
Laricobius nigrinus Fender is a Derodontid beetle that feeds on hemlock woolly adelgid on western hemlocks. This beetle is native to northwestern U.S. and Canada and was collected in 1997 to assess its potential of being a biological control for HWA. Laricobius is active in the winter and its lifecycle syncs up that that of the HWA.
Number: 1276018Description: Yellow egg amidst red hemlock woolly adelgid eggs
Photographer: Ashley Lamb, Virginia Tech
Laricobius beetles insert one egg per adelgid ovisac. The larvae will hatch, feed on the eggs and then drops to the ground and pupate. The pupae then aestivate during the summer in the soil and emerge around October when the adelgid also breaks aestivation.
Number: 1276019Description: Late instar larva
Photographer: Ashley Lamb, Virginia Tech
The larvae feeds exclusively on HWA eggs and will only complete development on HWA eggs.
Number:1276020Description:Pupa
Photographer:Ashley Lamb, Virginia Tech
Number: 1276021Description: Adult
Photographer: Ashley Lamb, Virginia Tech
The adults feed on all life stages of HWA from November until May.
Another species, Laricobius rubidus, is native to the eastern U.S. and feeds on pine bark adelgid. It has a similar life cycle to L. nigrinus except that it hibernates in the winter along with aestivating in the summer. L. rubidus has been collected from HWA infested eastern hemlocks and laboratory studies have showed that it can complete its lifecycle on HWA.
All Photographs taken from http://www.gainvasives.org/hwa/biocontrol.html