The Toxicity of Certain Synthetic Organic Compounds to the Fruit‐tree Red‐spider Mite

Abstract

The acaricidal activity of ninety synthetic organic compounds has been investigated in the laboratory. Considerable differences were found between the winter eggs, the summer eggs and the adult female stages of the fruit‐tree red‐spider mite (Meta‐tetranychus ulmi (Koch)) in their susceptibility to many of the compounds but two substances, namely azoxybenzene and n‐dodecyl thiocyanate, were appreciably toxic to all three stages. Of the compounds showing promise against summer eggs and mites, bis‐(p‐chlorophenyl) methyl carbinol and 4‐chloroazobenzene were the best, being highly toxic to both summer stages. Of the remainder, diphenylsulphone, 4‐chlorodiphenylsulphone, azobenzene and hydrazobenzene were highly ovicidal, while C12‐C13 alkyl thiocyanates and sec.‐dodecyl thiocyanate gave high kills of the adult female mite.Relationships between molecular structure and acaricidal activity have been sought. In a series of compounds characterized by the presence of two benzene nuclei connected by certain bridging groups, it has been found that activity to the summer stages of the mite can be influenced by alterations to the bridging group and by substitution in the benzene nuclei. Maximum activity appears to be associated with chlorine substitution in the para position in one nucleus and also with compounds of this type having unsubstituted nuclei.

Nematocidal Thiocyanatins from a Southern Australian Marine Sponge Oceanapia sp.

“…Researchers in the mid to late 1900s observed that alkyl thiocyanates could under appropriate enzymatic conditions release HCN, and they went on to explore the agrochemical potential of this effect. For example, C 12 and C 13 n-alkyl and sec-alkyl thiocyanates were noted to be outstanding insecticides against adult female fruit-tree red spider mites, 15 while various other alkyl thiocyanates were described as lethal to mice and houseflies 16 and selected beetles 17 through the action of HCN. Although these early investigations focused on synthetic alkyl thiocyanates, it has long been known that certain plants and insects employ HCN as a defensive agent through the intermediary of cyanogenic glycosides.…”

“…The residue was partitioned between H2O (10 mL) and Et2O (10 mL), and the aqueous phase extracted with Et2O (3 × 10 mL). The combined organic phase was washed with brine (10 mL), dried (anhydrous MgSO (15). A mixture of commercially available 9-bromo-1-nonanol (5 g, 22.4 mmol), dihydropyran (2.1 mL, 23.3 mmol), and concentrated HCl (22 µL) was stirred at RT for 18 h. The reaction mixture was diluted with Et2O (20 mL) and washed with H2O (20 mL), saturated NaHCO3aq (2 × 20 mL), and brine (20 mL), then dried (anhydrous MgSO4), filtered, and concentrated under reduced pressure.…”

East Mailing Research Station

“…The value of study of the inter-relation of the host plant and the pest or disease is illustrated by the work of Wormald (1932), the founder of the Plant Pathology Section, on Bacterial Canker, of Keyworth (1942) on the Verticillium W ilt diseases, of Moore (1950) on Brown R ot of apples, plums, etc., and by th a t of Dicker (1951) on fruit aphids, and of Massee and others on the Fruit Tree Red Spider Mite (Blair 1951). Parallel investi gations of control measures, of the mode of action of fungicides and insecticides (Eaton & Davies 1950), and of methods for their detailed study in the field and laboratory (Moore 1947;Steer 1937), have assisted in relating control measures to the biological characteristics of host and pest.…”

Properties and Actions of Bridged Diphenyl Acaricides

“…Eaton and Davies (13) found that diphenyl sulfone was an active acaricide but it was adversely phytotoxic. p-Chlorophenyl phenyl sulfone was also active, but bis(p-chlorophenyl)sulfone was less active.…”