Decreased severity of potato common scab after foliar sprays of 3,5 -dichlorophenoxyacetic acid, a possible antipathogenic agent

Glasshouse tests on the potato cultivars Majestic and Maris Bard measured the effects of single early foliar sprays of ring-substituted phenoxyacetic acids (0.9 × 10–³ M) on the incidence of potato common scab, caused by soil-borne Streptomyces scabies. The most effective compound was 3,5-dichlorophenoxyacetic acid (3,5-D), which decreased scab by about 90%; its action was preventative, early sprays being more effective than late However, it slightly decreased yield, and increased the number of tubers per plant and the proportion of deformed tubers. The trichloro- and tetrachloro- acids containing the 3,5-dichloro- group also decreased scab, though to lesser extents; the most active of these was the 2,3,4,5-tetrachloro- acid, which had the same side effects as 3,5-D. The herbicide 2,4-D almost halved scab incidence, but seriously decreased yield. Other acids tested had little or no effect on scab. In tests against S. scabies in culture, 3,5-D was no more toxic than other disubstituted acids which were inactive, or weakly active, against the disease in vivo. 3,5-D may be an ‘antipathogenic agent’, preventing scab development by altering tuber metabolism.     

THE CIRCULATORY SYSTEM OF THE ALDER FLY SIALIS LUTARIA

This is a comprehensive account of the circulatory system of all stages of Sialis lutaria L. The circulatory organs and pathways are described. In the larva an organ for circulating blood within the terminal segment is described. In the adult, blood vessels are described in the appendages and over the surface of the brain. Associated with these vessels are two types of accessory circulatory organs, pulsatile and valvular. The rates of heart beat, of circulation and pulsation of the scutellar organs are recorded.     

BIOLOGICAL EFFECTS OF A HEATED EFFLUENT IN DOCKS AT SWANSEA, S. WALES

Observations on the fauna of a heated, fully saline dock have been made by diving and by using suspended test panels. The seasonal abundance and breeding of native and immigrant species are described. The effects of subsequent cooling of the dock and the appearance of additional native species in the fauna are described and discussed.     

Aphid colonization of spring cereals

In 1970-1, Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae were the commonest alatae trapped from April/May to August, with most in July and early August. The first alatae appeared in the Rothamsted survey suction trap 0–34 days before aphids were found on the cereals, but during May and June no relationship was found between the numbers trapped and the number on the crop. Most species occurred first near the sheltered edge of the crop, but M. dirhodum was widespread over the field. Most infestations were quickly dispersed by the movements of older morphs; adults only stayed in one place for about 2 days. Alate M. dirhodum moved more often than apterae, but both morphs of S. avenae moved equally often and more frequently between larvipositions than did those of M. dirhodum. Apterae deposited more nymphs in a ‘group’ than alatae, and M. dirhodum deposited more than S. avenae. Few ‘groups’ persisted for more than a week. Although M. dirhodum occupied the crop area faster than S. avenae, all 0–3 m lengths of row sampled being infested within 2–5 wk of their first appearance, most or all of the tillers were colonized only in late July 1970.     

Application of the names Crataegus calycina Peterm. and C. oxyacantha L.

Authentic herbarium material of Crataegus calycina Petermann (1849) supports Hrabetová-Uhrová's contention in 1969 that this is conspecific with C. macrocarpa Hegetschweiler; the name C. calycina , for which a Petermann specimen in Musée Botanique Cantonal, Lausanne is designated as lectotype, had been incorrectly applied in Flora Europaea.
Examination of the specimens in the Linnaean Herbarium has led to acceptance of Dandy's proposal in 1946 that sheet 643.12 should be designated as the lectotype of C. oxyacantha L. (1753). This specimen is not, as frequently assumed, C. laevigata (Poiret) DC. (C oxyacanthoides Thuill.) but the species described in Flora Europaea as "C. calycina Peterm. subsp. curvisepala (Lindman) Franco". It is suggested that the name C. oxyacantha L. is a source of confusion and should be rejected under Article 69 of the International Code of Botanical Nomenclature. This gives priority to the name C. curvisepala Lindman, which should replace C. calycina Peterm. in Flora Europaea.     

THE SPECIFIC CHARACTERS OF THE CRESTED PORCUPINES, SUBGENUS HYSTRIX

The characters used for specific diagnosis in the subgenus Hystrix have been studied to determine their constancy as specific characters and their geographical variation within the species. As a result three species are recognized, namely H. indica, H. cristata and H. africaeaustralis. H. galeata is considered a synonym of H. cristata , and H. stegmanni a synonym of H. africaeaustralis . The morphological differences between cristata and africaeaustralis in East Africa are not continued clinally within these species. Between cristata and indica some of the diagnostic characters vary clinally, others change abruptly.     

THE NEUROENDOCRINE SYSTEM AND STOMATOGASTRIC NERVOUS SYSTEM OF THE ADULT TSETSE FLY GLOSSINA MORSITANS

The brain of Glossina morsitans Westwood contains four groups of neurosecretory cells which are stainable with chrome haematozylin and phloxin. The axons of these cells form a pair of nervi corporis cardiaci which pass posteriorly from the brain and innervate the corpora cardiaca and corpus allatum before uniting with a small ganglion posterior to the corpora cardiaca. This ganglion is considered to represent the fusion of the fusion of the hypocerebral and ventricular ganglia which remain separate in other insects.
There is no frontal ganglion in the adult Glossina and the recurrent nerve fuses with one of the nervi corporis cardiaci immediately behind the brain. The oesophageal nerves arising from the fused hypocerebral and ventricular ganglia innervate the oesophagus in the anterior part of the thorax, the proventriculus and the posterior extension of the oesophagus close to the crop. These nerves possess both sensory and motor nerve endings. The differences which exist between Glossina and other cyclorrhaphous Diptera with respect to their neuroendocrine/stomatogastric system are noted and considered in terms of the control of neuroendocrine function.