Effect of ammonium sulfate on the phytotoxicity, foliar uptake, and translocation of imazamethabenz in wild oat
Experiments were conducted in greenhouse, growth chamber, and laboratory conditions to determine the effect of ammonium sulfate [(NH4)2SO4] on the phytotoxicity, foliar uptake, and translocation of imazamethabenz on wild oat. Rates of (NH4)2SO4 up to 5% (w/v) applied with a greenhouse sprayer did not affect the phytotoxicity of the herbicide when the mix was applied at the one- to two-leaf stage. However, inclusion of 1 and 2% (NH4)2SO4 increased the phytotoxicity of the herbicide when the mix was sprayed at the two- to three-leaf, or the three- to four-leaf stage. At 10%, (NH4)2SO4 decreased the phytotoxicity of the sublethal dosage of the herbicide. When the herbicide was applied as individual drops to the growth chamber-grown plants, inclusion of (NH4)2SO4 at 1% did not affect phytotoxicity as measured by shoot growth. The presence of (NH4)2SO4 did not affect the amount of imazamethabenz retained by wild oat foliage, but it decreased [14C]imazamethabenz absorption, slightly antagonized acropetal translocation, and increased the basipetal translocation of [14C]imazamethabenz. It was concluded that application methods greatly modify the effect of (NH4)2SO4 on imazamethabenz phytotoxicity. Herbicide absorption and translocation as determined by one method do not necessarily represent the absorption and translocation patterns when different application methods are used. Absorption and translocation were not the factors that were responsible for the observed effect of (NH4)2SO4 on the herbicide phytotoxicity.
Effect of ammonium sulphate and related salts on the phytotoxicity of dichlorprop and other herbicides used for broadleaved weed control in cereals
Summary 
 
In glasshouse experiments, additions of 10–100 g 1−1 ammonium sulphate enhanced the phytotoxicity to broadleaved weeds and cereals of several water-soluble herbicides applied post-emergence in 75–300 1 ha−1 with hydraulic nozzles. Studies with dichlorprop potassium salt and chickweed Stellaria media (L.) Vill. examined interactions between ammonium sulphate and environmental, application and formulation factors. Simulated rainfall immediately after spraying greatly reduced dichlorprop activity, whether or not ammonium sulphate was present. However, when there was an interval of 2–24 h between spraying and rainfall, the additive increased phytotoxicity. Surfactants tended to reduce dichlorprop phytotoxicity to Stellaria media, both in the presence and absence of ammonium sulphate. Certain other inorganic salts including sodium sulphate also enhanced phytotoxicity. Applications by rotary atomizer in very low spray volume (15 1 ha−1, 250–280 μm drops) were less effective than conventional 150 1 ha−1 applications. When very low volume application was used, addition of ammonium sulphate or nitrate tended to reduce activity further. In the field, ammonium sulphate significantly increased the effects against weeds of a commercial dichlorprop potassium salt formulation applied conventionally in 200 1 ha−1 spray volume. Neutralized phosphoric acid had a similar effect but a mixture of this additive and ammonium sulphate reduced phytotoxicity. Both additives slightly increased dichlorprop injury to barley. 
 
Rasuma 
 
Effet du sulfate d'ammonium et de sels voisins sur la phytotoxicite du dichlorprop et d'autres herbicides utilises pour lutter contre les dicotyledones dans une culture de cereales 
 
 
 
Au cours d'experimentations menees en serre, l'addition de doses de sulfate d'ammonium, variant entre 10 et 100 g 1−1, augmente la toxicite de differents herbicides en solution aqueuse vis-a-vis des mauvaises herbes dicotyledones et des cereales, lorsqu'il est applique en postlevee avec des; buses hydrauliques permettant une application de 75 a 300 1 ha−1. Des etudes mettant en oeuvre le sel de potassium du dichlorprop applique sur de la stellaire (Stellaria media) ont permis d'observer des interactions entre le sulfate d'ammonium et les facteurs relatifs a l'environnement, a la technique d'application et a la formulation des produits. Une aspersion apportee immediatement apres la pulverisation, reduit tres fortement l'activite du dichlorprop qu'il y ait ou non apport de sulfate d'ammonium. Cependant lorsqu'une periode sans pluie de 2 a 24 h suit la pulverisation, l'adjonction de ce sel augmente la phytotoxicite. La presence de tensioactifs tend a reduire la phytotoxicite du dichlorprop vis-a-vis de Stellaria media qu'il y ait ou non adjonction de sulfate d'ammonium. Certains autres sels inorganiques, notamment le sulfate de sodium, augmentent egalement cette phytotoxicite. Des applications realisees par pulverisation centrifuge a tres bas volume (15 1 ha−1) semblent moins efficaces que les pulverisations traditionnelles a 150 1 ha−1. Lorsque de tres bas volumes sont utilises, l'addition de sulfate ou de nitrate d'ammonium tend a reduire encore plus l'activite des produits. Au champ, le sulfate d'ammonium augmente de facon significative l'efficacite contre les mauvaises herbes de formulations commerciales du sel d'ammonium du dichlorprop, lorsque l'application est faite au volume conventionnel de 2001 ha−1. L'acide phosphorique neutralisee a un effet similaire, mais l'association de cet adjuvant avec le sulfate d'ammonium reduit la phytotoxicite. Ces deux produits augmentent legerement l'aggressivite du dichlorprop vis-a-vis de l'orge. 
 
Zusammenfassung 
 
Wirkung des Ammonsulfats und verwandter Salze auf die Phytotoxizitat von Dichlorprop und anderen zur breitblattrigen Unkrautbekampfung in Getreidekulturen eingesetzten Herbiziden 
 
 
 
In Gewachshausversuchen wurde die Phytotoxizitat mehrerer wasserloslichen Herbizide gegenuber breitblattrige Unkrauter sowie Getreidepflanzen durch Zufugung von 10–100 g 1−1 Ammonsulfat erhoht. Die Behandlungen wurden im Nachauflauf in 75–300 1 ha−1 mit Spritzdusen gemacht. In Untersuchungen mit Dichlorprop Kalium und Vogelmiere (Stellaria media (L.) Vill) wurden Wechselwirkungen zwischen Ammonsulfat und Umwelts-, Anwendungs- und Formulkierungsfaktoren studiert. Simulierter Niederschlag unmittelbar nach der Spritzung fuhrte eine starke Aktivitatsminderung des Dichlorprops herbei, ungeachtet der Anwesenheit von Ammonsulfat. Jedoch bei einem Zeitabstand von 2 bis 4 Stunden zwischen der Spritzung und dem Niederschlag erhohte das Additiv die Phytotoxizitat. Netzmittel reduzierten im Allgemein die Phytotoxizitat von Dichlorprop gegenuber Vogelmiere, ungeachtet der An = oder Abwesenheit von Ammonsulfat. Auch gewisse andere anorganische Salze, einschliesslich Natriumsulfat, erhohten diese Phytotoxizitat. Anwendungen durch Rotationzerstauber mit sehr niedrigen Bruhmengen (15 1 ha−1, 250–280 μm Tropfen) waren weniger wirksam als konventionnelle 150 1 ha−1 Anwendungen. Bei ULV-Anwendungen reduzierte die Zufugung von Ammonsulfat oder Nitrat die Wirksamkeit noch mehr. Im Freiland wurde die Leistung einer kommerziellen, in 200 1 ha−1 konventionnell angewandten Kaliumsalzformulierung des Dichlorprops durch Ammonsulfat bedeutend erhoht. Neutralisierte Phosphorsaure wirkte ahnlich aus aber in einer Mischung mit Ammonsulfat reduzierte dieses Additiv die Phytotoxizitat des Dichlorprops. Durch beide Additive wurden die Dichlorpropschaden an Gerst leicht verstarkt.
The infection process, sporulation and survival of Alternaria helianthi on sunflower
SUMMARY 
 
Electron microscopy was used to study the infection of sunflower leaves by Alternaria helianthi. Conidia germinated by producing one to many germ tubes which grew across the leaf surface before forming appressoria. The fungus directly penetrated its host through the cuticle and epidermis. Entry into the host through wounds and stomates was also observed. Extracellular sheaths were found to be associated with germ tubes and intercellular hyphae of A. helianthi. Conidiophores developed through collapsed stomates, from leaf veins, trichomes and also from mycelium growing across the host leaf surface. Microcylic conidia were produced directly from parent conidia under certain conditions. Studies using a volumetric spore trap showed that the airborne spore concentration followed a distinct periodicity with peaks occurring between 0900 and 1100 h each day. Laboratory studies showed that safflower, noogoora burr and bathurst burr could serve as alternative hosts for A. helianthi. The pathogen was readily isolated from sunflower crop debris from a diseased crop that had been harvested 1 yr earlier.