Field tests with insecticides and insect growth regulators to control insect pests of cowpea and its effects on certain beneficial insects

A small‐plot tests were conducted on cowpea, Vigna ungiculata (L.) Walp, to determine the effectiveness of 14 selected insecticides representing four insecticide classes (organophosphates, carbamates, pyrethroids, and insect growth regulators, IGRs), and four insecticide/IGR mixtures on cowpea insect pests and its effects on certain beneficial insects. By day 3 after treatement, the insecticides phenthoate, isoxathion, cyanophos, carbaryl, and cypermethrin used at sub‐recommended rates reduced the leafhopper, Empoasca spp., populations by >83% than those in the control. On that day, all insecticide treatments significantly reduced the cowpea aphid, Aphis craccivora, numbers below that of the control. The prothiofos, isoxathion, pirimicarb, and fenpropathrin treatments provided continuing control to both leafhoppers and aphids through day 21 after spraying. It seems that most insecticide treatments were not effective in whitefly, Bemisia tabaci, control. The best control of the whitefly immatures was obtained by day 3 after spraying in plots received thiodicarb (76%) and fenpropathrin (60%). All selected insecticides and rates used had very low residual effect against B. tabaci immatures. By day 3 posttreatment, the carbaryl (2.02 kg/ha) caused completely protection for cowpea pods frMw blue pea butterfly, Lampides boeticus, larvae. The IGRs, flufenoxuron and Dowco‐439, applied alone and those applied in mixtures with insecticides, carbaryl/teflubenzuron, chlorpyrifos/XRD‐473, and methomyl/ flufenoxuron, exhibited satisfactory control (>81%) to butterfly larvae on day 7 posttreatment. All treatments did not exhibit a considerable residual activity against L. boeticus larvae through 2–3 weeks followed spray. Most insecticides applied at the higher rates used significantly reduced the numbers of limabean pod borer, Etiella zinckenella, larvae found in cowpea pods collected on day 7 after application. The IGRs, flufenoxuron and Dowco‐439, applied alone, at 0.119 kg/ha, or in mixtures, methomyl/flufenoxuron (0.167 kg/ha) and chlorpyrifos/Dowco‐439 (0.911 kg/ha) caused >73% control of E. zinckenella larvae through day 21 posttreatment. The best control of cowpea weevil, Callosobru‐chus spp., adults (>83%), on day 3 after spraying, was obtained in treatments of cyanophos (1.19 kg/ha), prothiofos (1.43 kg/ha), flufenoxuron (0.119 kg/ha), and chlorpyrifos/Dowco‐439 (0.911 kg/ha). The IGR flufenoxuron applied alone or in mixture, methomyl/flufenoxuron (0.164 kg/ ha) exhibited satisfactory residual activity against Callosobruchus adults through day 21 posttreatment. Percentage seed damage by the larvae of cowpea weevils was significantly lower in most treatments than that of control. Populations of insect predators found in all treated plots were extremely reduced than those found in untreated plots. By day 21 after spraying, the IGRs flufenoxuron, XRD‐473, and Dowco‐439, applied at the low rate of 0.071 kg/ha, seemed to be less effect against insect predators than other insecticides used.     

Diversity of Sertoli cells in the testis of Saduria entomon L. (Crustacea,Isopoda)

Summary

The present paper is the first to give a comprehensive and detailed characterization of Sertoli cells in the isopod, Saduria entomon, based on transmission electron microscopy. Two types of Sertoli cells, A and B, were distinguished which clearly differ in their location in the wall of the testicular tubule, and in their morphology, ultrastructure, and function. Their occurrence is closely connected with the characteristic arrangement of germ cells inside the tubule. Sertoli A cells occupy only the part of the tubule containing spermatogonia and primary spermatocytes and they are associated with these cells by means of numerous ramified processes running in many directions. They are irregular in shape, but their shape and the ultrastructure are stable during maturation of the germ cells. Sertoli B cells, which compose most of the testicular tubule wall, form a columnar epithelium. They send long processes into the lumen of the tubule by means of which they make contact with maturing spermatids. The cytoarchitecture of the processes is highly variable and reflects their role in spermiogenesis and the formation of sperm bundles. After spermiation, when the apical part of the Sertoli cells has become flattened, they phagocytoze the residual cytoplasmic masses of spermatids, which undergo degradation in heterophagic vacuoles. Simultaneously, numerous autophagic vesicles appear.     

The Significance of Leaf Area in Evapotranspiration

Evapotranspiration rates increased with leaf area and fell withits decline at the time of flowering of cotton plants (Gossypiumbarbadense L.) and this relation was maintained while the rateof pan evaporation was steadily decreasing. A similar relationshipwas established for the hyacinth bean (Dolichos lablab L.) butevapotranspiration dropped at the onset of flowering, at thetime when leaf area was still increasing and the evaporatingpotential of the atmosphere began to rise. Evapotranspirationper unit area of leaf surface per day declined progressivelywith age for both species.     

Evaluation of the consequences of stress factors on plant seeds growing in a 30-km zone of Balakovo AES

The effect of stress factors (small doses of radiation and maximum temperatures in the econiche of the tested plants (tmax)) as well as aging on pea seeds, both acting independently and in combination, is estimated. Here we evaluate the influence of oxidizing stress on pea seeds in the laboratory (gamma-irradiated with 7 cGy at 0.3-19.1 cGy/h, tmax approximately 30-32 degrees C) and on natural plantain seeds collected in a 30-km zone of NPP (radiation exposure approximately 15 R/h, tmax approximately 38-40 degrees C). We have mathematically modeled CAs frequencies in root seedlings meristeme by invoking an enhancing factor transmitted from cell to cell. It is shown under the stress conditions: 1) CA frequency decreases whereas the fraction of inviable seeds (IS) increases, the dependence of IS on CA frequency being inversed; 2) a stimulation of proliferation of cell was observed; 3) a bystander effect appears; 4) antioxidative status (AOS) of seeds influences on adaptation on the all levels of the organization; 5) IS increases up to 73-80% under the combined effect of radiation and heat stresses.     

The antioxidant status of the seeds in populations of the great plantain (Plantago major L.) growing in an area exposed to the Balakovo Atomic Electric Power Station and to chemical enterprises

The results of the determination of radionuclide and chemical (multielement analysis) soil pollution are presented. The data on antioxidant status of plantain (Plantago major L.) in conjunction with the data on radionuclide and chemical pollution are analyzed. The most significant decrease in antioxidant activity of plant seeds was observed in areas situated along the most frequent wind direction in the region in summer 1998. It is suggested that lower antioxidant status is caused by the chronic radionuclide release on the chemically polluted territories.