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Rouhollah SOBHIAN Progress Report

October 1999 to August 2000

 

Travel

 

1- Uzbekistan (with M. Cristofaro), 28 Sept. to 6 October; to establish two field plots for testing four Acroptilon insects (the perennial test plants were grown).

 

2- The USA, 24 to 29 October; to participate in W-185 meeting in Albuquerque, NM, and visit to the ARS Lab in Albany, CA, and CDFA Lab in Sacramento, CA.

 

3- Uzbekistan (with Urs Schaffner), 2 to 10 April; to grow the annual test plants in the two Acroptilon plots and to grow type A and type B Salsola plants to be tested against a gall midge found in UZ.

 

4- Tunisia (with A. Kirk), 12 to 23 May; to collect Tamarix samples for DNA analysis, collect natural enemies of Tamarix, and collect Plutella larvae, pupae and parasitoids.

 

5- Uzbekistan, 18 to 30 June; to take data from the Acroptilon and the Salsola field plots.

 

6- Turkey, Greece, and Bulgaria, 17 to 24 July; to bring US-Tamarix cuttings to Turkey to be tested against Liocleonus, verify the status of the host specificity tests on Salsola in Greece, and collect Plutella samples from Greece and Bulgaria.

Short report on various projects

 

Acroptilon repens: Two field plots with nine test plant species (10 replicates/species) were established in Uzbekistan to study the host specificity of four insects discovered by R. Sobhian in Uzbekistan. One plot was 60 km from Tashkent in the area where A. repens and its natural enemies occur and the second plot was at the garden of the Zoological Inst. in Tashkent where no Acroptilon was present (the four natural enemies were added to the plots).These were two species of Urophora, seed feeders, (under study by Jeff Littlefield at MSU, Bozeman), a lepidopteran root borer and a hymenopteran stem gall maker (under investigation by U. Schaffner). The studies were carried out in collaboration with U. Schaffner (CABI Bioscience, Delemont) and Jeff Littlefield (MSU).

 

The seed heads of the test plants were collected periodically and will be examined for infestations by Urophora spp. The galls of the gall wasp were found only on A. repens. The lepidopteran root borer will be released on the plots and the number of eggs laid on each plant will be registered during August 2000. The experiment will end in August, but the examination of the seed heads may take a few months. Urs Schaffner was taking also data from Napomyza, a root crown/stem mining Agromyzid fly that was found also in Turkey. So far, the field data confirms the host specificity of the natural enemies tested.

 

Salsola project: DNA analysis of various populations of Salsola (Russian thistle) from California, carried out by Fred Ryan, showed two distinct biotypes of the plant. These were referred to as type A and type B. Seeds of Type A and type B were provided by F. Ryan, to be tested with the natural enemies that were selected for biological control of the weed. Seeds of other test plants were provided by M. Pitcairn. The following studies were carried out or are on the way during 2000:

 

a) A field test in Uzbekistan with the gall midge Desertovellum stackelbergi (Cecidomyiidae): Seeds were grown in April and transplanted in a field by mid May, where natural population of the gall midge and Salsola were present. Data were taken from the plants on June 25 and July 15. On 25 June, 26 of the 38 type A and one of 39 type B plants were infested by the midge. On July 15, all the plants of the type A and five more of the type B plants (total six plants) were infested. The results of the experiment shows that the insect has a strong preference for type A , but attacks also type B. An insect that can distinguish between the biotypes of Salsola, must be specific to S. kali, its original host host.

 

b) No choice laboratory test in Montpellier on Piesma salsolae (Hemiptera : Piesmatidae). Type A and B Salsola seeds from California and local Salsola (control) were grown along with 18 other plant species or varieties (7 var. sugar beets, 2 var. table beets, 2 var. chards, 1 North American native plant, etc.). In total 21 plant species or varieties were tested. Adult feeding and oviposition was observed on most of the plants including the beets.
Adults lived up to two weeks and laid eggs in Petri dishes without any food. Larval development was observed on most plants including the beets even though much slower than on Salsola . No significant difference was observed between type A, type B, and local Salsola. If we obtain adults on the beets, we will verify if they lay eggs (they may be sterile !). Unfortunately, the results are not as good as we expected.

 

c) Host specificity test on Gymnancella canella (Lep. : Pyralidae) : Seeds of the same plants, as for Piesma, were grown and will be inoculated with freshly emerged larvae from eggs.

 

d) Host specificity of the mite Aceria salsolae (Acari : Eriophyidae): Seeds of 10 test plants were sent to J. Kashefi in Greece. The seeds are grown and will be tested with the mite. A number of plants were tested last year in Greece and the mite attacked only Salsola.

 

Cardaria draba, hoary cress: The weevil, Ceutorhynchus pleurostigma Marsh., is a gall maker that attacks the upper parts of the roots and root crowns of C. draba. According to the literature, the insect is a pest on cabbage and many other cruciferus plants. However, when I grew three var. of cabbages near Montpellier, in 1995, no galls could be found on these, while the Cardaria plants growing at the same site were attacked. Therefore, I thought we may be dealing with a different species or race that could be specific to C. draba. A field test was carried out in Montpellier using three var. of cabbages, Prennial pepper weed, and C. draba (control), with 10 replicates of each plant species or varieties. No galls were found on other test plants, while 85 % of the Cardaria plants were infested. We visited many cultivated fields around Montpellier (conventional and biological growing) such as colza, radish, cabbage (different varieties), turnip, etc., but did not find any infestation by the weevil on the cultivated plants. Several French agricultural institutions such as INRA and plant protection Institutes were contacted to find out if they knew of any such damage to their cruciferous crops. Apparently they do not have any problem with this weevil. We are going to present a paper on this subject at the XI weed symposium in Dijon, France in September this year (together with B. Fumanal and A. Blanchet).

We will continue our studies on this insect.

 

Euphorbia esula, leafy spurge: A gall midge, Spurgia capitigena (Dipt. : Cecidomyiidae), adapted to moist and heavy soil, was found in France by R. Sobhian. Studies on the insect was carried out in collaboration with M. Cristofaro and J. Littlefield. The first shipment of the insect was sent to the USA for release in Montana during May 2000.

 

Tamarix spp.: Host specificity test on the weevil, Liocleonus clathratus (Col. : Curculionidae): It is a root gall maker, which according to the literature should be specific to Tamarix spp. An agreement has been made with Prof. N. Uygur the chairman of the Dept. of herbology, at the Fac. of Agriculture in Adana, Turkey, to study the host specificity of the insect. Cuttings of T. ramosissima and T. aphilla, from the USA, were hand carried to Adana to be tested with the insect. The weevil is over one cm. long and their larvae need fairly large roots for development. Therefore, the plants will be grown in large pots this year (10 species or var. with 10 replicates each) and will be tested in 3-4 years.

Many Tamarix samples were collected from Uzbekistan, Turkey, and Tunisia for DNA analysis. In addition, insects were collected from many locations in Tunisia, using sweeping net or visually. A technician of the plant protection Inst. in Tunis has been hired to check the presence or absence of Diorhabda elongata. The aim of the study was to see if the insect is active during the summer months or it has an aestivation period. The biotype that has been imported to the USA from China aestivates.

 

Galium project (for Canada): Host specificity of the new species of the gall mite Cecidophyes rouhollahi, found near Montpellier a few years ago, was finished. The mite attacks only a few closely related weedy species of Galium. However, presence of a virus in the galls made by Cecidophyes galii on G. aparine near Paris, prevented us to submit a petition for release of C. rouhollahi in North America, before making sure that the galls made by this mite on Galium spp. are free of virus. An agreement has been made with M. Peterschmit, a virologist at CIRAD Montpellier, to carry out the necessary studies on the subject. Field collected mites were lab cultured for several generation and galls produced by these were provided to M. Peterschmit for the studies. If it turns out that the galls are free of virus, then we will submit a petition for release of the mite in Canada for biological control of G. spurium, which occures also in the USA.

 

Plutella project: Since A. Kirk and I could not collect any Plutella material on our trip in Tunisia, I promised to collect samples of the insect from other countries. A sample of about 600 specimens from Uzbekistan and a sample of over 100 specimens from Greece were collected and hand carried to D. Bordat, who is collaborating with A. Kirk.

Publications

 

1- Sobhian, R., Tunç, I, Erler, F. 1999. Preliminary studies on the biology and host specificity of Aceria salsolae and Lixus salsolae, two candidates for biological control of Salsola kali. J. Appl. Ent. 123, 205-209.

 

2- Craemer Charnie, Sobhian Rouhollah, McClay Alec, and Amrine James 1999. A new species of Cecidophyes (Acari: Eriophyidae) from Galium aparine (Rubinaceae) with notes on its biology and potential as a biological control agent for Galium spurium. International journal of Acarology , Vol.25, No.4, 225-263.

 

3- Hasan Siraj, Sobhian Rouhollah, Knutson Lloyd 1999. Preliminary studies on Ramularia crupinae sp. nov. As a potential biological control agent for common crupina (Crupina vulgaris) in the USA. Ann.appl.Biol.,135: 489-494

 

4- Quimby, P.; Kirk A. A.; Sobhian, R.; Campobasso, G.; Kashefi, J. 1999. A perspective after 40 years research at the USDA/ARS European Biological Control Laboratory. Brighton Confrence: Weeds, Vols 1-3 Farham: British Crop Protection Council. P. 303-306.

 

5- Sobhian Rouhollah, Littlefield Jeff, Cristofaro Massimo, Kimberli Mann (in Press). Biology and host specificity of Spurgia capitigena (Bremi) (Diptera : Cecidomyiidae), for the biological control of Euphorbia esula L. in North America. Journal of Applied Entomology , in Press.

 

6- Fumanal B. , Blanchet A., and Sobhian R. September 2000. Ceutorhynchus pleurostigma Marsh (Coleoptera: Curculionidae), a candidate for biological control of Cardaria draba (L.), hoary cress, (Brassicaceae) in the USA. XI th Conference on weeds. Dijon 6-8 September, 2000. Accepted for an oral presentation.