Persistence and phytotoxicity of napropamide residues in soil

The time for 50% loss of napropamide following incorporation into a sandy loam soil in the field varied from about 130 days when applied in spring or early summer to over 200 days when applied later in the year. When left on the soil surface, up to 75% of the applied dose was lost during the first 28 days after application in June or July, whereas losses following application in November, December or January represented less than 25% of the amounts applied. These losses following surface application were closely correlated with the amounts of incoming solar radiation. First-order half-lives for degradation in nine soils incubated moist at 20°C in the laboratory varied from 72 to 150 days. They were positively correlated with the extent of herbicide adsorption by the soils and with their clay content, and negatively correlated with soil pH. Phytotoxicity to wheat and barley in the same soils in glasshouse experiments was inversely related to their organic matter content and to the extent of herbicide adsorption. Wheat was more tolerant of the herbicide than was barley. The results are discussed in terms of possible carryover problems with napropamide in some crop rotations.     

Some British species of Anagrus (Hymenoptera: Mymaridae)

Five species of Anagrus , egg parasites of various leafhopper species (Delphacidae and Cicadellidae, Honioptera), were bred for 3–13 generations in laboratory conditions. Biological and niorphological characteristics as well as attempts at crossbreeding were used to recognise the species Anagrus ensijer Debauche and four new. species. A. ensifer occurred in two varieties. The four new species and the two varieties of A. ensifer are described, and a key is given to both sexes.     

Cellulose xanthate as a soil conditioner: implications for weed control with some soil-applied herbicides

Applications of cellulose xanthate equivalent to 50 kg cellulose/ha to fresh seedbeds preserved surface microtopography and prevented capping after rainfall. Numbers of weed seedlings were up to 50% greater than on untreated soil where capping occurred. The efficiency of nine soil-acting herbicides was not impaired when applied at normal rates either before or after cellulose xanthate. There was no evidence of interaction and the numbers of surviving weeds were proportional to the numbers where no herbicide had been applied. With propachlor, however, weed control was consistently less when applied shortly before or after cellulose xanthate, and analyses showed that in the presence of the soil conditioner the rate of herbicide loss was enhanced. This effect decreased the longer propachlor application was delayed, but was still evident with an interval of 96 h.