Infection process of Rhizoctonia solani on Solanum tuberosum and effects of granular nematicides

The infection process ofRhizoctonia solani AG-3 was studied on potato sprouts, cv. Bintje, in growth chamber trials at 15 °C. Initially hyphae ofR. solani grew predominantly in the longitudinal direction of the sprouts (runner hyphae). They tended to follow the junctions between epidermis cells as was observed by SEM. The hyphae formed side-branches mainly half-way of the subterranean parts of the sprouts. They branched several times with short swollen cells to form infection cushions. Lesions developed only underneath the infection cushions and were first observed five days after inoculation. The necrotic area was proportional to the area covered with infection cushions on the sprouts. Depth of the lesions could extend up to the vascular bundle. Sprouts were colonized only in healthy tissue in the epidermal layer underneath the infection cushion and in necrotic tissue. A few days after appearance of the lesions,R. solani formed brown, uninfective mycelium on and in the circumference of these lesions.Aldicarb did not influence any part of the infection process. Ethoprophos delayed the emergence of sprouts, but increased the number of sprouts per tuber. As soon as sprouts had emerged, growth was considerably promoted by ethoprophos. Ethoprophos delayed the appearance of lesions and reduced their size. Oxamyl showed the same effects to a smaller extent.As the size of lesions appears to be proportional to the size of the infection cushions, any agents that change the size of the infection cushions, such as pesticides or antagonists, may alter the severity of the disease.Samenvatting Het infectieproces vanRhizoctonia solani AG-3 werd bestudeerd op aardappelspruiten, cv. Bintje, in een klimaatcel bij 15C. Aanvankelijk groeide de schimmel met runnerhyfen voornamelijk in de lengterichting van de spruit. Via SEM kon waargenomen worden, dat de hyfen hierbij vooral over de begrenzingen van de epidermiscellen groeiden. Het mycelium vormde veel zijvertakkingen, bestaande uit iets gezwollen korte cellen, welke voornamelijk halverwege op het ondergrondse deel van de spruit gevormd werden. Een dichte massa van deze cellen vormde een infectiekussentje. Lesies, welke vanaf vijf dagen na inoculatie werden waargenomen, bevonden zich slechts onder spruitoppervlak bezet met infectiekussentjes. De lesiegrootte was recht evenredig met het spruitoppervlak dat bezet was met infectiekussentjes. De diepte van de lesies reikte tot aan de vaatbundels. De spruit werd alleen door de schimmel gekoloniseerd in gezond epidermisweefsel onder het infectiekussentje en in necrotisch weefsel. Enkele dagen na verschijning van lesies vormde R.solani bruin, niet infectieus, mycelium op en rondom de lesies.Aldicarb had geen effect op het infectieproces. Ethoprophos vertraagde de opkomst en verhoogde het aantal tot ontwikkeling gekomen spruiten per knol in gestoomd zand. Direct na opkomst had ethoprophos echter een sterk groeistimulerend effect. Ethoprophos vertraagde de lesievorming en reduceerde de lesiegrootte, vergeleken met onbehandelde planten. Oxamyl vertoonde deze effecten in geringere mate.Daar de lesiegrootte direct gecorreleerd blijkt met de grootte van het infectiekussentje, mag verwacht worden dat elke beïnvloeding van de ontwikkeling van het mycelium van R.solani, bijvoorbeeld door pesticiden of antagonisten, een verandering van de lesiegrootte ten gevolge heeft.     

Sarcoma development after radiotherapy in two dogs

Two dogs were treated with a hypofractionated course of radiotherapy following surgical excision of an intermediate grade mast cell tumour and a round cell tumour, respectively. Both dogs developed a sarcoma of the bone, within the irradiated site, several years after the initial radiotherapy treatment. Bone tumours arising within a previously irradiated area are well‐recognized late radiotherapy side‐effect in humans but have been reported infrequently in dogs. These are the first case reports to describe bone sarcomas in the appendicular skeleton at a site, which had been previously treated by a hypofractionated course of radiotherapy for an unrelated tumour.     

Ovicidal and nymphicidal effects of some fungicides on the greenhouse whitefly<Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis>

Eggs and L1 nymphs of the greenhouse whiteflyTrialeurodes vaporariorum (Westwood) (Hem.: Aleyrodidae) on bean leaves were directly sprayed with the fungicides maneb and mancozeb at recommended rates for practical use. Strong ovicidal and nymphicidal effects were observed. These fungicides may prove to have practical use for integration in IPM programs for whitefly control, as they also exert low or no toxicity to the whitefly parasitoidEncarsia formosa. http://www.phytoparasitica.org posting April, 30, 2004.     

The impact of phenology,exposure and instar susceptibility on insecticide effects on a chrysomelid beetle population

Direct topical impact of an insecticide spray on a population of a non-target leaf-eating beetle, Gastrophysa polygoni, was studied, and the relative importance of phenology, instar susceptibility and instar specific exposure was evaluated. Two insecticides, cypermethrin and dimethoate, were investigated. In the laboratory, topical toxicity to eggs, second-instar larvae and adults was recorded in dose-response experiments. The spatial distribution of larvae and eggs were measured in the field. Deposition of insecticide onto eggs, second-instar larvae and adult specimens was measured at different positions within the crop canopy by use of a dye tracer technique. A temperature-driven population model was constructed to simulate population development of all life stages in the field. The model was based on laboratory measures of growth and development at various temperatures. Mortality due to direct insecticide exposure was calculated as a function of population demography, spatial distribution of individuals, spatial deposition of the insecticide, and stage-specific susceptibility. Cypermethrin had the greatest impact, reducing population size by 19–32%. The life stages most sensitive to cypermethrin were the larval instars. As the population developed from eggs to larvae and imagines, the impact of one spraying first increased and then decreased according to the proportion of larvae in the population. Dimethoate had less effect on the population, i.e. 1·9–7·6% reduction. Dimethoate was most toxic to the egg stage, and consequently the effect on the population decreased as the proportion of eggs decreased due to hatching. The direct effect of insecticide spraying was significantly affected by all three factors investigated, i.e. phenology, life stage susceptibility and stage-specific exposure. The latter factor is composed of both spray flux at various spatial positions in the canopy and the ability of different life stages to retain spray droplets. © 1998 SCI     

The side-effects of pesticides onDiaeretiella rapae, a parasitoid of the turnip aphid (Lipaphis erysimi)

Diaeretiella rapae (M’Intosh.) is an endoparasite of the turnip aphid,Lipaphis erysimi (Kalt.) with a wide geographical distribution. The four Pesticides Nogos 50 EC at 600 ml per acre, Dimecron 50 WSC, Monofos 40 WSC and Tamaron 600 SL at 500 ml per acre, used in practice for the control of this pest, were tested for their side-effects onD. rapae. The parasitoid was reared on pottedBrassica napus plants infested with aphid under laboratory conditions (22±2°C, 60–70% rel. hum., 16 h light and 8 h dark). In one test, adult female parasitoids were exposed to fresh pesticide residues on glass plates and in another test, the pupae within aphid mummies were directly sprayed. The results revealed that Dimecron 50 WSC, Nogos 50 EC and Monofos 40 WSC were harmful causing 100% mortalitv toD. rapae followed by Tamaron 600 SL (97% moderately harmful) after 24 hours of application, compared to no mortality in control, where only water was sprayed. Directly spraying of pupae with Dimecron 50 WSC and Nogos 50 EC reduced adult parasitoid emergence to 9 and 7%, respectively, Monofos 40 WSC and Tamaron 600 SL to 3% compared to 78% emergence for the control within one week of treatment. The results showed that none of the tested pesticides was safe toD. rapae and according to the International Organization for Biological Control (IOBC) further testing under semi-field and field conditions is recommended.     

Systemic effects of topical and subconjunctival ophthalmic atropine in the horse

OBJECTIVE: To identify any systemic effects of topical and subconjunctival administration of atropine sulfate in the horse. Animals studied Six mature grade horses were treated hourly in one eye with topical ophthalmic atropine drops for 24 h. Five horses were treated subconjunctivally in one eye with 3 mg of atropine sulfate. Procedures Pupillary light reflexes, pupil size, electrocardiographic parameters, girth measurements, intestinal motility, and clinical signs of abdominal pain were monitored. RESULTS: Alteration in auscultated gut motility and clinical signs of abdominal pain were the most sensitive indicators of the systemic manifestations of the topically applied atropine. Gut motility was absent in all horses for periods of 2-18 h in all four abdominal quadrants in horses given topically administered atropine. Signs of abdominal pain were observed in four of six horses that received topical atropine. In the subconjunctival test study, gut motility was absent in three horses for periods of 3-7 h. Uniocular subconjunctival injection of 3 mg atropine sulfate produced signs of abdominal pain in one of six horses. Conclusion The ophthalmic administration of atropine can affect gut motility and induce signs of colic in selected horses.     

动物专用头孢噻呋

头孢噻呋是第1个动物专用的第3代头孢菌素类抗生素,具有抗茵谱广,抗茵活性强,给药后吸收迅速,生物利用度高,半衰期长,药效持久等特点.近年来,在兽医临床上的应用日趋广泛.论文从头孢噻呋的理化性质、抗茵活性、抗生素后效应、药代动力学特征、临床应用、不良反应和头孢噻呋在动物性食品中的残留检测等方面进行了综述.为该药在兽医临床应用提供参考.     

Insecticide selectivity and behavioral response of the earwig Doru luteipes

Insecticide lethal and sub-lethal effects on non-target species are a focus in pest management programs. However, such studies are usually centered in relatively few groups of natural enemies of insect pests. Earwigs, although insect pest predators of key importance in Neotropical maize fields, have received very little attention. The earwig Doru luteipes (Sccuder) (Dermaptera: Forficulidae) is one of the main predators of the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). Both species were subjected to toxicity and selectivity studies with the insecticides chlorantraniliprole, chlorfenapyr, chlorpyrifos, λ-cyhalothrin, deltamethrin, etofenprox, methomyl and spinosad. The behavioral locomotory response of D. luteipes to these compounds was also assessed. Concentration-response bioassays indicated very low potency of chlorantraniliprole (>550,000× less toxic), followed by spinosad (>3,500× less toxic) and etofenprox (>1,100× less toxic) as compared to chlorpyrifos, the most toxic insecticide studied against this earwig species. These same three compounds exhibited the highest selectivity when comparing the earwig with its prey, the fall armyworm. Time-response bioassays using the insecticide label rates recommended against the fall armyworm confirmed the high selectivity of chlorantraniliprole and etofenprox, in addition to deltamethrin and methomyl. Again chlorpyrifos exhibited the lowest levels of selectivity. Exposure of the earwig to insecticide-treated surfaces indicated that spinosad reduced the locomotory activity of the adults probably increasing their insecticide exposure, while they avoided chlorfenapyr-, etofenprox-, and chlorpyrifos-treated surfaces. Chlorantraniliprole and etofenprox seem the most promising compounds for use against S. frugiperda whilst preserving populations of D. luteipes.