The Cabbage Field.

The painting represents a figure bending over to attend the plants in a cabbage field, probably the artist's summer house in Wannsee outside Berlin, where he did most of his work after 1922.

Biological control of prickly acacia: Current research and future prospects

Prickly acacia, Vachellia nilotica subsp. indica (syn. Acacia nilotica subsp. indica) (Fabaceae), a major weed in the natural grasslands of western Queensland, has been a target of biological control since the 1980s with limited success to date. Surveys in India, based on genetic and climate matching, identified five insects and two rust pathogens as potential agents. Host-specificity tests were conducted for the insects in India and under quarantine conditions in Australia, and for the rust pathogens under quarantine conditions at CABI in the UK. In no-choice tests, the brown leaf-webber, Phycita sp. A, (Lepidoptera: Pyralidae) completed development on 17 non-target plant species. Though the moth showed a clear preference for prickly acacia in oviposition choice trials screening of additional test-plant species was terminated in view of the potential non-target risk. The scale insect Anomalococcus indicus (Hemiptera: Lecanodiaspididae) developed into mature gravid females on 13 out of 58 non-target plant species tested. In the majority of cases very few female scales matured but development was comparable to that on prickly acacia on four of the non-target species. In multiple choice tests, the scale insect showed a significant preference for the target weed over non-target species tested. In a paired-choice trial under field conditions in India, crawler establishment occurred only on prickly acacia and not on the non-target species tested. Further choice trials are to be conducted under natural field conditions in India. A colony of the green leaf-webber Phycita sp. B has been established in quarantine facilities in Australia and host-specificity testing has commenced. The gall-rust Ravenelia acaciae-arabicae and the leaf-rust Ravenelia evansii (Puccineales: Raveneliaceae) both infected and produced viable urediniospores on Vachellia sutherlandii (Fabaceae), a non-target Australian native plant species. Hence, no further testing with the two rust species was pursued. Inoculation trials using the gall mite Aceria liopeltus (Acari: Eriophyidae) from V. nilotica subsp. kraussiana in South Africa resulted in no gall induction on V. nilotica subsp. indica. Future research will focus on the leaf-weevil Dereodus denticollis (Coleoptera: Curculionidae) and the leaf-beetle Pachnephorus sp. (Coleoptera: Chrysomelidae) under quarantine conditions in Australia. Native range surveys for additional potential biological control agents will also be pursued in northern and western Africa.

Field and laboratory evaluation of fungicides for the control of Phytophthora fruit rot of papaya in far north Queensland, Australia

Results from the first of two artificially inoculated field experiments showed foliar applications of copper hydroxide (Blue Shield Copper) at 600 g a.i./100 L−1 (0% infected fruit), copper hydroxide + metalaxyl-M (Ridomil Gold Plus.) at 877.5 g a.i./100 L−1 (0.27%), metiram + pyraclostrobin (Aero) at 720 g a.i./100 L−1 (0.51%), chlorothalonil (Bravo WeatherStik) at 994 g a.i./100 L−1 (0.63%) and cuprous oxide (Nordox 750 WG) at 990 g a.i./100 L−1 (0.8%) of water significantly reduced the percentage of infected fruit compared to potassium phosphonate (Agri-Fos 600) at 1200 g a.i./100 L−1 (8.22%), dimethomorph (Acrobat) at 108 g a.i./100 L−1 (11.18%) and the untreated control (16%). Results from the second experiment showed fruit sprayed with copper hydroxide (Champ Dry Prill) at 300 (2.0% infected fruit), 375 (0.4%) and 450 g a.i./100 L−1 (0.6%) and metiram + pyraclostrobin (Aero) at 360 (2.8%), 480 (0.6%) and 600 g a.i./100 L−1 of water (1.0%) significantly reduced the percentage of infected fruit compared to the untreated control (19.4%). Foliar sprays of copper hydroxide at 375 g a.i./100 L−1 in rotation with chlorothalonil at 994 g a.i./100 L−1 every two weeks is now recommended to growers for controlling Phytophthora fruit rot of papaya.

Photoimpedance characterization of polymer field-effect transistor

The small signal ac response is measured across the source-drain terminals of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) field-effect transistor under dc bias to obtain the equivalent circuit parameters in the dark, and under a monochromatic light (540 nm) of various intensities. The numerically simulated response based on these parameters shows deviation at low frequency which is related to the charge accumulation at the interface and the contact resistance at the electrodes. This method can be used to differentiate the photophysical phenomena occurring in the bulk from that at the metal-semiconductor interface for polymer field-effect transistors. ©2009 American Institute of Physics