European Pine Resin Midge | Cecidomyia pini (DeGeer)

California Pest Rating  for
European Pine Resin Midge | Cecidomyia pini (DeGeer)
Diptera: Cecidomyiidae
Pest Rating: A



Initiating Event:

Cecidomyia pini is currently Q-rated.  A permanent pest rating proposal is required to support an official pest rating.

History & Status:

Background:  Adult Cecidomyia pini are delicate flies with a brown-black color (DeGeer, 1776).  The size was not found by the author of this proposal, but adults of other Cecidomyia species are 2-5 mm in length.  The larvae of C. pini are yellow-red in color and are found on needles of Abies (fir), Picea (spruce), and Pinus (pine) species.  The larvae apparently feed on accumulations of resin on the needles (Barnes, 1951).  Gagné (1978) stated that Cecidomyia species are “primary feeders and cause extensive damage to pines.”  However, the literature is equivocal regarding the impact of C. pini on host trees.  Barnes (1951) considered C. pini not to be economically significant.  It is possible that C. pini feeds on resin that is released from pre-existing injuries, for example, feeding damage caused by another insect (Barnes, 1951; Felt, 1906).  Two sources suggest that C. pini causes damage to pine cones, including the death of cones and the loss of seeds (Dormont et al.; 1996; Roques et al., 2017).  Other species of Cecidomyia are reported to cause damage to pines, including gall-like deformities (California Forest Pest Control Action Council, 1968; Ferrell et al., 1987; Gagné, 1978; Reeks, 1960).    The larvae of Cecidomyia pini build cocoons on the needles and pupate in them.

Worldwide Distribution:  Cecidomyia pini is found in northern and central Europe (Gagné and Jaschhof, 2017).

Official Control: Cecidomyia pini is not known to be under official control anywhere.

California Distribution:  Cecidomyia pini is not known to be present in California (Symbiota Collections of Arthropods Network).

California Interceptions:  Cecidomyia pini may have been intercepted on conifer wood dunnage intercepted in San Francisco in 1987 (CDFA Pest and Damage Report Database, 2018).

The risk Cecidomyia pini would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Cecidomyia pini is reported from a large area, including much of Europe. This suggests that the climate of much of California would be suitable for the species.  Cecidomyia pini is known to feed on at least three conifer genera, including Pinus, and there may be suitable host trees throughout California.  It is likely that pini could become established over a large portion of California.  Therefore, C. pini receives a High (3) in this category.

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Cecidomyia pini is known to feed on at least three genera of coniferous trees. Therefore, it receives a Medium (2) in this category.

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Reproductive and Dispersal Potential: Adult pini presumably fly, although it is not known how far they are capable of flying.  Therefore, it receives a Medium (2) in this category.

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Cecidomyia pini has been reported to impact pine seed production (but see Uncertainty, below).  If this species became established in California, it could impact regeneration of pine trees, which could impact timber yield. Therefore, it receives a Low (1) in this category.

Economic Impact:  A

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 1

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Cecidomyia pini is reported to impact pine seed production (but see Uncertainty, below). If this species became established in California, it could threaten rare pines, including Bolander’s beach pine (Pinus contorta bolanderi) and Torrey pine (Pinus torreyana torreyana) (Calflora).  Therefore, it receives a Medium (2) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  B

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Cecidomyia pini: Medium (10)

Add up the total score and include it here.

–Low = 5-8 points

–Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Cecidomyia pini is not known to be present in California.  It receives a Not established (0) in this category.

–Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (10)


The most important uncertainty in this proposal is the potential for C. pini to impact plants.  The biology of this species does not appear to be well-known.  Two sources (cited above) suggest that this species causes damage to pine cones, resulting in loss of seeds.  This species is very widely distributed, and it seems likely that it is not causing significant damage in its current range if only for the fact that there are so few reports of damage.  It is not known if natural enemies in its native range (which may not be present in California) regulate the amount of damage inflicted by C. pini.  It is possible that the damage to the pine cones in the reported cases was caused by another insect and this damage was blamed on the C. pini, which could have simply taken advantage of the release of resin.  It is possible that C. pini poses no threat, economic or environmental, to California.

Conclusion and Rating Justification:

Cecidomyia pini is a widespread European fly that is not known to occur in California.  It feeds on conifer resin on living trees, and reports suggest that it causes damage to trees.  Because of the possibility of damage to living conifers in California, this species may pose an economic and environmental threat to this state.  For these reasons, an “A” rating is justified.


Barnes, H. F.  1951.  Gall midges of economic importance, Volume V: Gall midges of trees.  Crosby Lockwood & Son Ltd., London.

Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals, including the Consortium of California Herbaria.  Accessed March 26, 2017:

California Forest Pest Control Action Council.  1968.  Forest pest conditions on California – 1967.  California Division of Forestry.

DeGeer, C.  1776.  Memoires pour server a l’histoire des insectes, Volume 6.  Pierre Hesselberg, Stockholm.

Ferrell, G. T., Bedard, W. D., and Jenkinson, J. L.  1987.  Gouty pitch midge damage to ponderosa pines planted on fertile and infertile soils in the western Sierra Nevada.  United States Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station, Research Note PSW-390.

Gagné, R. J.  1978.  A systematic analysis of the pine pitch midges, Cecidomyia spp. (Diptera: Cecidomyiidae).  United States Department of Agriculture Technical Bulletin 1575:1-18.

Gagné, R. J. and Jaschhof, M.  2017.  A catalog of Cecidomyiidae (Diptera) of the world, 4th edition.  Accessed April 25, 2018:

Reeks, W. A.  1960.  Observations on the life history, distribution, and abundance of two species of Cecidomyia (Diptera, Cecidomyiidae) on jack pine in Manitoba and Saskatchewan.  The Canadian Entomologist 92:154-160.

Roques, A., Talgø, V., Fan, J. -T., and Auger-Rozenberg, M. -A.  2017.  Damage to flowers, cones and seeds of coniferous woody plants.  Pp. 89-223 in Roques, A., Cleary, M., Matsiakh, I., and Eschen, R. (eds.), Field Guide for the Identification of Damage on Woody Sentinel Plants.  CABI, Oxfordshire, United Kingdom.

Symbiota Collections of Arthropods Network.  Accessed March 26, 2017:



Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741;[@]

Responsible Party:

Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211,[@]

Comment Period:* CLOSED

6/27/18 – 8/11/18


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Pest Rating: A


Posted by ls