Control of Morningglories (Ipomoea spp.) in Sugarcane (Saccharum spp.)
Abstract Morningglories are summer annual or perennial dicots, and are troublesome weeds in sugarcane cultivated in northern India. If not controlled, they may compete with sugarcane, interfere in the harvest operation, and reduce yields. Managing morningglories in sugarcane continues to be a serious challenge for sugarcane growers. Field experiments were conducted during the 3-yr period from 2007 to 2009 to evaluate herbicides applied PRE and POST for control of morningglories in sugarcane. The herbicides applied PRE included diuron, metribuzin, and atrazine at 1.6, 1.4, and 1.0 kg ai ha−1, respectively, applied alone or followed by 2,4-D amine salt (0.58 or 1.16 kg ae ha−1) or 2,4-D sodium salt (0.8 or 1.6 kg ae ha−1) applied POST. Herbicides applied PRE controlled morningglories ≤ 87% at 15 d after treatment (DAT); however, control reduced to ≤ 56% at 90 DAT. Control improved when herbicides applied PRE were followed by POST application of 2,4-D amine or sodium salt. For example, diuron applied PRE followed by 2,4-D amine salt applied POST at any rate provided 100% control of morningglories at 15 and 30 DAT. At 90 d after POST application, control ranged from 68 to 82% with the PRE followed by POST herbicides, compared to 0% control when metribuzin or atrazine were applied PRE alone. The density and biomass of morningglories was also reduced to zero in treatments that included 2,4-D amine salt. The number of millable canes, cane height, and single cane weight was superior in PRE followed by POST herbicide treatments compared to herbicides applied PRE alone. Maximum cane yield was recorded for the treatments that included 2,4-D amine or sodium salt compared to only PRE treatments, and it was usually comparable with the nontreated weed-free control. It is concluded that a combination of PRE and POST herbicides were effective for control of morningglories; however, more research is required to evaluate other herbicides and their tank mix partners for control of morningglories in sugarcane. Nomenclature: Japanese morningglory, Ipomoea nil (L.) Roth.; obscure morningglory, Ipomoea obscura L. Ker Gawl.; sugarcane, Saccharum spp.
Photochemical transformation of atrazine and formation of photointermediates under conditions relevant to sunlit surface waters: laboratory measures and modelling.
By combination of laboratory experiments and modelling, we show here that the main photochemical pathways leading to the transformation of atrazine (ATZ, 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) in surface waters would be direct photolysis, reaction with ·OH and with the triplet states of chromophoric dissolved organic matter ((3)CDOM*). Reaction with (3)CDOM* would be favoured by elevated water depth and dissolved organic carbon content, while opposite conditions would favour direct photolysis and OH reaction. Desethylatrazine (DEA, 4-amino-2-chloro-6-isopropylamino-1,3,5-triazine) was the main detected intermediate of ATZ phototransformation. Its formation yield from ATZ (ratio of DEA formation to ATZ transformation rate) would be 0.93 ± 0.14 for ·OH, 0.55 ± 0.05 for (3)CDOM*, and 0.20 ± 0.02 for direct photolysis. Direct photolysis and ·OH reaction also yielded 4-amino-2-hydroxy-6-isopropylamino-1,3,5-triazine (DEAOH) and 6-amino-2-chloro-4-ethylamino-1,3,5-triazine (DIA). Reaction with excited triplet states also produced 2-hydroxy-4,6-diamino-1,3,5-triazine (AN) and 2-chloro-4,6-diamino-1,3,5-triazine (CAAT). Therefore, if biological processes can be neglected and if the low formation yields do not prevent detection, DEAOH and DIA could be used as markers of ATZ direct photolysis and ·OH reaction, while AN and CAAT could be markers of ATZ reaction with (3)CDOM*. Model predictions concerning ATZ phototransformation were compared with available field data from the literature. When sufficiently detailed field information was provided, good agreement was found with the model.
Redescription of two ghost shrimps (Decapoda: Axiidea: Callianassidae) from the Middle Miocene of the Central Paratethys: systematics, intraspecific variation, and in situ preservation
A redescription of two Middle Miocene burrowing ghost shrimps of the Central Paratethys, Callianassa brocchii L renthey, 1897 and Callianassa pseudorakosensis L renthey in L renthey & Beurlen, 1929, is provided. Material forming the basis of this study comes from the Studienka Formation (lower 'Sarmatian', Serravallian) of the Slovak part of the Vienna Basin and exhibits preservation allowing reassignment of the studied taxa to the genera Neocallichirus Sakai, 1988 and Eucalliax Manning & Felder, 1991 respectively. The major cheliped of both species exhibits two distinct morphotypes interpreted herein as possible sexual dimorpism. Several specimens of both taxa are preserved within the tube structures and are interpreted as in situ preservation within the burrows. Type material of both studied taxa and additional collections from the roughly coeval strata of Hungary and Austria were also studied.