biocontrol insects
Dr. Gitta Grosskopf-Lachat is the lead biocontrol researcher at CABI working on the hawkweed insects. CABI researchers and MSU research Dr. Jeff Littlefield have collected and tested eight insect species for three invasive hawkweeds. The three invasive hawkweeds targeted for biocontrol are:
- mouse-ear hawkweed (P. officinarum, H. pilosella)
- orange hawkweed (P. aurantiaca, H. aurantiacum)
- meadow hawkweed (P. caespitosa, H. caespitosum, H. pratense)
The biocontrol insects damage the stolons, roots, and stems of the plant impacting seed production and limited spread. Three of the initial eight insects were found to feed on native species in host-specific testing so now the testing is limited to five remaining insects.
Hawkweed plants used for biocontrol open field
insect testing.
gall wasp
The parthenogentic gall wasp (Aulacidea subterminalis) ovipositions into the stolons of orange and mouse-ear hawkweeds in host range testing. Currently, the gall wasp screening is being completed at Montana State University (MSU) by Dr. Jeff LIttlefield. MSU hopes to submit a peitition for release of this insect to the Technical Advisory Group (TAG) in 2009. MSU and CABI have been mass rearing the insects in quarantine since 2008 in anticipation that this insect will be approved for release.
The Gall wasp (Aulacidea subterminalis)
ovipositing on hawkweed.
Insect galls on mouse-ear hawkweed.
hover fly
The two hover flies (Cheilosia urbana, Cheilosa psilophthalma) impact different parts of of the hawkweed plant. C. urbana impacts the roots while C. psilophthalma eats the above-ground plant parts. A petition to the Technical Advisory Group (TAG) is currently being compiled by Dr. Gitta Grosskopf-Lachat for Cheilosia urbana in 2009. Testing for Cheilosa psilophthalma is progressing slowly because it is less common in the field. Preliminary results reveal invasive hawkweeds in open-tests are not attacked. However, more testing is need for this insect.
Hover fly (Cheilosa urbana) impacts hawkweed
roots.
Hover fly (Cheilosa psilophthalma) eats above-ground
plant parts.
NEW! stem gall wasps
Two different populations of stem gall wasps (Aulacidea hieracii and Aulacidea pilosellae) are currently being investigated. These gall wasps reduce the number of flower heads and inhibit flowering of hawkweed plants. One population was collected in the Ukraine and the other one in Russia. The Ukraine population has already shown impacts on the meadow hawkweeds and the first round of tests are being conducted on the Russian insects in 2009.
Aulacidea hieracii galls on meadow hawkweed.
Aulacidea pilosellae ovipositing into a stolon.
More research is needed on these new stem gall wasps. However, Hawkweed Biocontrol Consortium funds have decreased and this project will not continue until more money is secured. To contribute to the Hawkweed Biocontrol Consortium, please contact marijka@uidaho.edu.
new Zealand insects
There are also many insects released on hawkweeds in New Zealand where they too are invasive. There are four invasive hawkweed species in New Zealand with the most troublesome being mouse-ear hawkweed (Hieracium pilosella). Five insects have already been approved for release in New Zealand. New Zealand does not have any native hawkweeds so the biocontrol approval process has progressed more quickly than in North America.
gall midge
The gall midge (Macrolabis pilosellae) has been released for biocontrol on invasive hawkweeds in New Zealand and is now established in the field. The multivoltine gall midge galls the rosette center, flower heads, and stolen tips of hawkweeds. Larval feeding on the leaf tissue prevents the unfolding of the leaves. In no-choice tests the gall midge did develop on most native North American Hieracium spp. so this agent was removed from the list of potential North American agents.
Female gall midge (Macrolabis pilosellae)
ovipositing.
For more information on hawkweed biocontrol research, contact Gitta Grosskopf-Lachat.