Effect of grain type on the insecticidal efficacy of SilicoSec against Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

The insecticidal efficacy of the diatomaceous earth formulation SilicoSec^® (Agrinova GmbH, Germany) against the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) was evaluated on peeled rice, paddy rice, maize and barley in laboratory tests. SilicoSec was applied at five dose rates: 0.125, 0.25, 0.5, 1 and 1.5 g/kg of grain. The treated grains were infested with S. oryzae adults, and the weevil mortality was estimated after 24, 48 h, 7 and 14 d of exposure on treated grain. After the 14 d counts, all the exposed adults were removed and progeny production on treated grains was assessed 45 and 90 d later. Insecticidal efficacy of SilicoSec against the rice weevil was highly affected by grain type, exposure interval and dose rate. In all grains tested, longer exposure intervals increased weevil mortality. The efficacy of SilicoSec on maize was not satisfactory, given that after a 14 d exposure at the highest dose rate the mortality did not exceed 65%. Moreover, progeny production on treated maize was high, regardless of the dose rate. On the other hand, 100% of weevils were dead on barley treated with the two highest dose rates of SilicoSec, after a 7 d exposure. However, a complete suppression of progeny production on treated barley was not achieved, even at the highest dose rate. A satisfactory level of protection was recorded on paddy rice treated with 1 and 1.5 g of SilicoSec/kg. At these two rates, all adults were dead after a 7 d exposure, and no progeny were produced during the 90 d incubation period. In contrast, the mortality on peeled rice treated with 1.5 g of SilicoSec/kg did not reach 100%, even after 14 d of exposure, and a high number of progeny were recorded.     

Development and growth of two Lesquerella species grown under different temperatures during the reproductive period

The genus Lesquerella is a promising source of hydroxy fatty acids (HFA). Several species such as Lesquerella fendleri and Lesquerella mendocina are candidate crops for arid and semi-arid cropping systems. Several reports are available on the environmental effects on growth and yield in Lesquerella, but information on the effect of temperature on plant growth and development specifically during the reproductive period in Lesquerella is limited. The objective of this work was to determine the effect of two contrasting thermal regimes after flowering on time to maturity, plant growth and biomass allocation to the different organs in L. fendleri and L. mendocina. A greenhouse experiment was conducted with plants grown at a range of 11–23 °C during the vegetative phase. After this stage, 50% of the plants of each species remained under the same temperature regime until maturity, whereas the other 50% was transferred to another module subjected to a range of 17–31 °C until maturity. The duration of the reproductive phase was reduced by 23 days in plants of both species in the 17–31 °C treatment compared to those at 11–23 °C, although no differences were observed when the length of the reproductive phase was measured in thermal-time units. Total plant biomass for both species was 20% greater in the 11–23 °C treatment. In L. fendleri, this increment occurred due to more vegetative shoot biomass, whereas in L. mendocina it was associated with greater reproductive and root biomass. No changes in biomass allocation were produced by temperature in L. fendleri, while in L. mendocina the lower temperature regime increased allocation to the reproductive organs, at the expense of a lower allocation to vegetative shoot. These results could be used to predict the specific temperature effects after flowering on yield under field conditions, and suggest that L. mendocina might be a promising perennial alternative for cooler sites.     

Incidence and population fluctuation of Diuraphis noxia in Hungary

A yellow water pan trap was used to collect Diuraphis noxia (Mordvilko) in Central Hungary in 1989. In 1990 a Rothamsted-type suction trap collected 31 individuals. A D. noxia infestation was found in an autumn-sown wheat field in October 1990. The D. noxia population that overwintered was holocyclic. The life-span of fundatrices was 43.2 days at 18–22°C. The number of nymphs produced per fundatrix was 46.6. Average progeny numbers of first-generation apterae and alatae were 29.4 and 21.4, respectively. Second-generation apterae produced an average of 48.8 nymphs; 35.9% of nymphs were alatiform. The D. noxia population reached its peak on 3 July in the field, at which time the mean number of individuals per wheat plant was 3953.6. By 20 July, the wheat plants had matured and the D. noxia colonies had disappeared from the wheat.     

Cereal leaf beetle (Oulema melanopus (L.)) population densities and winter wheat yields

Grain yields of a soft white winter wheat cultivar, cv. Ionia, susceptible to cereal leaf beetle (Oulema melanopus (L.)), were determined when the crop was subjected to four controlled infestation levels of the beetle in caged plots over a 3-year period in Michigan. Although identical infestation procedures and insect numbers were used each year, the intensity of larval infestation and feeding damage varied with the year. Significant (P < 0·01) grain losses occurred in plots that had at least 9·0 larvae per stem. The greatest yield loss was 45% and occurred with 15 larvae per stem and 85% feeding damage. Beetle damage had a greater effect on kernel weight than on the other yield components. Although economic thresholds should be conservative to allow for environmental variations, it appears that soft white winter wheat can often withstand beetle infestation levels greater than the current economic threshold of three or more eggs and largae per stem before the boot stage or one or more large larvae per flag leaf during heading.     

Effects of relative humidity and high temperature on spore germination and development of tomato powdery mildew (Leveillula taurica)

The effects of relative humidity (RH) and temperature on tomato powdery mildew (Leveillula taurica) were studied in controlled environments to define conditions that affect disease development in fresh market tomatoes in California. Gradients of RH (20–90%) at constant temperatures (20–30°C) were generated in single growth chambers to determine their effect on mildew development on mature tomato plants. Temperatures of 30°C and above were deleterious for spore germination, germ tube elongation, and disease development. Lesion growth and rate of disease progress were significantly higher at 20°C than at 25°C. Low RH levels (20–40%) reduced spore germination and lesion growth, accelerated host tissue death and reduced disease progress. Intermediate RH levels (50–70%) increased spore germination and optimized disease development, provided temperatures were maintained within favorable limits. High RH levels (80–90%) were favorable for spore germination but continued exposure to these conditions led to a limited lesion growth and disease progress. Short daily periods (two or three daily exposures of at least 2 h) of high temperatures (35°C) suppressed disease development by 70–92%.     

不同采集地割手密种质资源的耐寒性评价

本研究对不同采集地割手密无性系进行耐寒性综合评价,探究割手密耐寒性与其生长地海拔、纬度的关系,筛选耐寒性种质资源。以40份割手密无性系为试验材料,在苗期低温胁迫后测定各无性系材料的7项生理指标,利用相关性分析、聚类分析和模糊隶属函数分析法对其耐寒性差异进行综合评价。低温胁迫处理后,割手密的脯氨酸(Pro)、丙二醛(MDA)、电导率(PMP)、可溶性蛋含量(SP)均呈上升趋势,其中脯氨酸含量上升最大,升高了43.81%,而叶绿素(Chl)、超氧化物歧化酶(SOD)、过氧化物酶(POD)均呈下降趋势,其中叶绿素含量减少35.01%,下降程度最大;叶绿素、脯氨酸、超氧化物歧化酶的变异系数较对照有不同程度的增加,其中增长最大的是叶绿素,是对照的1.76倍;相关性分析显示,40份割手密无性系耐寒性与其生长地的海拔、纬度呈极显著正相关,相关系数分别为0.867、0.686;模糊隶属函数和聚类分析将40份割手密无性系的耐寒性分为三类,其中高耐寒类型有10份材料,中耐寒性有19份,不耐寒性11份。研究结果表明,不同采集地割手密材料之间耐寒性指标存在明显差异;耐寒隶属函数与海拔、纬度呈极显著正相关,即高海拔和高纬度的割手密耐寒性强、低海拔和低纬度的割手密耐寒性弱,表明在相近海拔范围内决定耐寒性的主要因素是纬度,在相近纬度范围内决定耐寒性的主要因素是海拔。该结果为割手密种质资源在甘蔗耐寒育种中的进一步利用提供依据。     

Pre-transplant herbicides for weed control in irrigated onion (Allium cepa L.) in northern Nigeria

Field trials were conducted at Samaru in the northern Guinea and at Bakuta and Kadawa in the Sudan Savanna ecological zones of Nigeria to identify suitable herbicides for weed control in irrigated onion. The herbicides tested were chlorthal-dimethyl, fluorodifen and oxadiazon. In the trials each herbicide treatment was compared with an identical treatment which received supplementary hand-weeding. The results of these experiments show that oxadiazon at 1·0–2·0 kg a.i./ha, with or without supplementary hoe-weeding at 6 weeks after transplanting, combined effective weed control with high bulb yields in irrigated dry season onions. While fluorodifen at 1·5 kg a.i./ha followed by supplementary hoe-weeding may be effective at sites with low weed infestation, a higher rate (3·0 kg/ha) may be desirable at sites with a higher broad-leaved weed infestation. Chlorthaldimethyl at 10·0 kg a.i./ha effectively controlled weeds at all the sites and gave high onion yields at sites with 6–12% clay; the selectivity was, however, lower at Bakura with very light soil. Uncontrolled weed growth caused 49–86% reduction in the bulb yields compared with the best herbicide treatments.     

Control of Bromus species in winter barley in England using EPTC

EPTC was tested in glasshouse and field experiments for its potential as a herbicide to control Bromus species in winter cereals. Bromus hordeaceus, Bromus commutatus, Bromus pectinatus and Bromus sterilis were all selectively controlled in barley by EPTC. Winter wheat was found to be susceptible but winter barley tolerated doses up to 2·0 kg a.i./ha. The barley cultivar Sonja was more resistant than both Athene and Maris Otter. In the first field trial, 1·0 kg a.i./ha EPTC reduced B. sterilis plant numbers by 75% giving a barley yield increase of 2·84 t/ha. In the following year 2·0 kg a.i./ha reduced B. sterilis numbers by 54% and increased yield by 1·75 t/ha.     

Relationship between leaf injury and colonization of cabbage by Sclerotinia sclerotiorum

Mechanical and insect feeding injuries of cabbage provided sites for ingress by Sclerotinia sclerotiorum. In field studies, injuries sustained by hitting cabbage heads with a blunt object penetrated several leaf layers and were readily infected by S. sclerotiorum. Incidence of Sclerotinia rot ranged from 15 to 36% infected plants in the hitting treatment. Disease incidence was low (0–5%) when wounds were created by allowing lepidopterous larvae (the imported cabbageworm, Pieris rapae L., the diamondback moth, Plutella xylostella L., and the cabbage looper, Trichoplusia ni Hubner) to feed on cabbage leaves. The incidence of colonization of lepidopterous larvae feeding sites by S. sclerotiorum was greater in greenhouse studies (5–60% infected feeding sites) than in field studies. In greenhouse studies, disease incidence was significantly greater in plants receiving hitting injuries than tearing injuries. There was little evidence of inoculation day or injury day effects. Colonization frequency of tissue injured mechanically was similar whether wounds were inoculated immediately or 4 days later. Plants that were incubated in a dry environment developed fewer infections than plants held in a moist environment. Inoculated plants that were not injured did not develop disease.     

Postharvest biological control of grey mould (Botrytis cinerea Pers.: Fr.) on fresh-market tomatoes with Bacillus amyloliquefaciens

Antagonistic bacteria were evaluated for their effectiveness in postharvest control of grey mould on fresh-market tomatoes. Grey mould was reduced in fresh-market tomatoes treated with antagonists and artificially inoculated with Botrytis cinerea, and stored at 20 °C for at least 7 days. One strain, 5PVB (Bacillus amyloliquefaciens) was particularly effective. This strain apparently did not produce extracellular antibiotic substances, yet was highly active against the pathogen on both mature-green and red tomatoes. Treatment with 5PVB before storage at 10 °C showed only fungistatic activity against grey mould. Chilling-injured mature-green tomatoes were more susceptible to B. cinerea. On chilled fruits the bacterial antagonist completely controlled the pathogen if the treatment was applied immediately after storage at 2 °C. In fermentation tests on four industrial waste materials, B. amyloliquefaciens grew well and maintained its antagonistic activity when grown in two of them. In pilot experiments with wounded fruits dipped in the bacterial cell and pathogen suspension, the development of decay was effectively inhibited.     

Red-winged blackbird (Agelaius phoeniceus L). feeding response to oil and anthocyanin levels in sunflower meal

Bird damage to sunflowers might be reduced by the development of resistant cultivars. Neagra de Cluj may be one such cultivar, with high levels of anthocyanin (a possibly aversive flavour) in achene hulls, but low oil yield. Four experiments were designed to assess the importance of oil content and anthocyanin concentration in feeding preferences expressed by red-winged blackbirds (Agelaius phoeniceus L.). Differences in oil concentration of 15% (w/w) were reliably discriminated in two-choice tests: higher concentrations were preferred. Conversely, all anthocyanin concentrations (0·5, 1·0, 2·5 and 5·0% [w/w]) were avoided, and two-choice tests suggested that higher concentrations (2·5 and 5·0%) were relatively more aversive. Both anthocyanin concentration and oil content could influence Neagra de Cluj resistance to bird depredation. Of these two characteristics, oil may be relatively more important.     

Efficacy of insecticides against major insect pests of potatoes in hot climates of Peru

Soil-incorporated and foliar-applied insecticides, alone and in combination, were tested in two different tropical sites of Peru. At San Ramon (altitude 800 m) major pests during the wet season were Diabrotica spp. and Myzus persicae. Soil-incorporated insecticides gave protection against Diabrotica but not M. persicae, and yields were significantly lower with these compared with the foliar-applied insecticide, carbofuran. Mean yield was inversely and significantly correlated with mean number of Diabrotica individuals per plant (r=0·989; 0·01 <P<0·05). The foliar-applied insecticide, season, major pests were Phthorimaea operculella, M. persicae and Feltia spp. Mean yield was inversely correlated with mean number of larval mines by P. operculella on foliage (r=0·976;0·02 <P<0·05). The foliar-applied insecticide methomyl, reduced pest damage and increased yields significantly. The major pests during the dry season at Yurimagus (altitude 180m) were Diabrotica spp. Foliar application of carbaryl alone, or in combination with soil-incorporated insecticides, was equally effective in reducing damage and yield loss. An inverse significant correlation (r=0·985; 0·01<P<0·02) for yield vs. damage from Diabrotica spp. was observed.     

Effects of sulfosulfuron soil residues on barley (Hordeum vulgare), sunflower (Helianthus annuus) and common vetch (vicia sativa)

The phytotoxicity and sensitivity of succeeding crops to the new sulfonylurea, sulfosulfuron, have been reported although there is insufficient data on the phytotoxic effect of field soil residues. Growth chamber bioassays were conducted to detect the presence of residues in soil samples previously treated with sulfosulfuron at the recommended rate and double rate (20 and 40 g a.i./ha) that could affect the succeeding crop. Soil samples were collected between 7 and 9 months after sulfosulfuron application in field selectivity assays at nine different locations in Northern and Central Spain. The bioassay test species were barley (Hordeum vulgare L.) ‘Graphic’, sunflower (Helianthus annuus L.) ‘Albasol’ and common vetch (Vicia sativa L.) ‘Neska’, typical crops grown in rotation with wheat (Triticum aestivum L.) in this area. Sulfosulfuron residues did not affect barley and common vetch, but inhibited shoot length, root length and root dry weight of sunflower seeded into some soils treated with the 2× rate (40 g a.i/ha) 9 months earlier.     

Latent infection of Botrytis cinerea in rose flowers and combined chemical and physiological control of the disease

A high percentage of rose flowers collected during winter from greenhouses around Israel developed grey mould disease when incubated in the laboratory in favourable conditions. Symptomless flowers of various cultivars were incubated in a humidity chamber after surface disinfection. More than 50% of the symptomless flowers yielded the pathogen Botrytis cinerea Pers., thus showing the presence of latent infection which probably occurred 3–8 days earlier in the commercial greenhouses. Initially, the symptoms which occurred on affected petals were mainly restricted lesions. However, when flowers were incubated under favourable conditions, necrosis developed and spread. Chemical control of grey mould was tested on cut rose flowers. Partial control of the disease was correlated with reduction in necrosis and a relative increase in restricted lesions (<2 mm in diameter). Of the 18 fungicides which were tested, the following were the most efficient during incubation at 20°C: metomeclan, dichlofluanid, myclozolin, N-phenylcarbamate plus carbendazim (NPC + MBC), polyoxin D, prochloraz and iprodione. When incubated at 10°C, the most effective fungicides against grey mould of rose flowers were NPC + MBC, polyoxin D, chlorothalonil, the detergent Tween 20, and the inhibitor of ethylene activity, silver thiosulphate (STS). Diphenylamine was more effective at 4°C than at 10° or 20°C. STS in combination with each of the fungicides chlorothalonil, polyoxin B, myclozolin or merpan was additively more effective than STS or each of the respective fungicides alone.     

Yield responses of garlic (Allium sativum L.) to oxadiazon, date of planting and intra-row spacing under irrigation at Kadawa, Nigeria

Field experiments were conducted in the 2002/2003 and 2003/2004 dry seasons at the Irrigation Research Station of the Institute for Agricultural Research, Kadawa (11°39′N, 38°02′E, 500 m above sea level) in the Sudan Savanna Ecological Zone, Nigeria to study the effects of oxadiazon, date of planting and intra-row spacing on yields of garlic (Allium sativum L.) under irrigation at Kadawa, Nigeria. A uniform inter-row spacing of 15 cm was maintained in the two seasons. The results obtained showed that the hoe-weeded plots and application of oxadiazon at 1.5 and 2.0 kg a.i./ha resulted in comparable but significantly higher bulb yield per hectare, bulb diameter, bulb weight and number of cloves than oxadiazon at l.0 kg a.i./ha and unweeded check. Bulb yield per hectare, bulb diameter, bulb weight and number of cloves were higher at early November planting. Planting garlic at 5 cm intra-row spacing resulted in higher bulb yield in both seasons.     

Acetylation of wheat straw hemicelluloses in N,N-dimethylacetamide/LiCl solvent system

Hemicellulose acetates were prepared under homogeneous reaction conditions in the system N,N-dimethylacetamide/lithium chloride by reacting the native hemicelluloses with acetic anhydride in the presence of 4-dimethylaminopyridine within 72 h at 60–85°C. The products obtained were characterised by means of Fourier transform infrared chromatography, gel permeation chromatography, and thermal analysis. The degree of substitution of acetylated hemicelluloses ranged between 0.74 and 1.49 as a function of experimental conditions. Under an optimum reaction condition (85°C, 60 h), over 80% hydroxyl groups in native hemicelluloses were acetylated. The molecular weight measurements showed that a significant degradation and hydrolysis of the products appeared at only a prolonging period of 72 h. It was found that the thermal stability of the products increased by esterification.     

Possible alternative utilization of Cynara spp.: I. Biomass, grain yield and chemical composition of grain

Globe artichoke (Cynara scolymus L.) and cultivated cardoon (C. cardunculus L. var. altilis DC.) are horticulturally important crop plants. These species have potential as biomass and oilseed crops. We field tested, for 3 years, two artichoke and two cardoon cultivars and one wild cardoon (C. cardunculus L. var. sylvestris Lam.) population on the Sicilian plain of Catania (37°27′ N, 15°04′ E, 10 m a.s.l.). On a 3-year average, the dry aboveground biomass resulted about 31 t ha⁻¹ in both cultivated cardoons, 18.8 t ha⁻¹ in wild cardoon, 13.7 t ha⁻¹ in globe artichoke ‘3/10 V.S.’ and 9.9 t ha⁻¹ in globe artichoke ‘374’ F₁. The caloric values of aboveground biomass (except for seeds), which was not significantly different among genotypes, ranged between 16 005 and 17 028 KJ kg⁻¹ of dry matter. The cultivated cardoon ‘Gigante di Lucca’ had the greatest grain yield (on 3-year average, 2.6 t ha⁻¹), whereas the two globe artichokes had the lowest yield (on 3-year average, 0.5 t ha⁻¹). Regardless of genotypes and years, the grains contain 20.1% crude protein, 24.4% oil, 18.5% crude fiber and 4.1% ash (dry weight basis). The grains of globe artichokes showed the highest crude protein content (21.6%), whereas those of cardoons the highest oil content (25.2%).     

A study on soil solarization and combined with fumigant application to control Phytophthora crown blight (Phytophthora capsici Leonian) on peppers in the East Mediterranean region of Turkey

Field trials conducted in the pepper growing area ( çel/Turkey) showed that solarization alone and combined with a reduced dose of methyl bromide (40 g/m²), were effective in controlling crown blight disease caused by Phytophthora capsici. Solarization was achieved by covering plots with a clear polyethylene sheet, 0.03 mm thick for 8 weeks. The temperature reached 47 °C and 35 °C at 5 cm and 30 cm soil depth, respectively, an average of 3–8 °C higher than those at equivalent depths in the untreated plots. The average incidence of the disease in solarization plus a reduced dose of methyl bromide, the recommended dose of methyl bromide, solarized and untreated plots in 1991 and 1992 were 17.6 and 13.3%; 20.8 and 16.8%; 24.1 and 19.7%; 39.8 and 42.9%, respectively. All treatments significantly reduced disease incidence.     

Levels of resistance of rice cultivars and the weed Leersia hexandra L. to Nephotettix malayanus Ishihara et Kawase and N. virescens (Distant)

Studies on the mechanisms of resistance of some rice cultivars and the weed, Leersia hexandra, to Nephotettix malayanus indicated low survival and popu;ation growth of the insect on resistant cultivars. Tests on feeding behaviour indicated that more feeding punctures were made on resistant than on susceptible cultivars. The amount of honeydew excreted was not related to the levels of resistance. Honeydew excreted on resistant cultivars was acidic (pH 5·08–6·92) and on susceptible L. hexandra, basic (pH 7·56). On the basis of the quality of honeydew excreted, N. malayanus was considered to be predominantly a xylem feeder. A test on the serial transmission of the rice tungro virus (RTV) showed that N. malayanus transmitted the virus for only one day after feeding acquisition. N. virescens was a more efficient vector of RTV than N. malayanus. N. malayanus prefers to feed on L. hexandra rather than on the rice cultivars tested.     

Overwintering and population dynamics of Bemisia tabaci biotype B in greenhouse during the spring in northern China

Since the sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B invaded southern China in the mid-1990s, it had spread to most other regions of the country, and become an important pest in agricultural and horticultural production. Investigations on overwintering of B. tabaci biotype B and its spring reproduction in northern China were conducted to determine the main factors that might contribute to an understanding of the population dynamics of this pest for developing improved pest control strategies. A cold hardiness test showed that when exposed for 10 h at −10 °C, mortalities of eggs, nymphs, and adults reached to 86.6%, 88.4%, and 100%, respectively, suggesting that it is probably impossible for feral populations of B. tabaci to survive in the winter under natural environmental conditions in northern China. A survey on vegetables, ornamental plants and weeds in greenhouses at Hebei Province and Beijing in northern China revealed at least 14 species of plants on which B. tabaci fed during the winter and spring. Lycopersicon esculentum Mill, Brassica alboglabra Bailey, Ficus carica L., Euphorbia pulcerrima Wild, and Hemelia patens Haence were the main host plants. Further research on the population dynamics of B. tabaci on three major greenhouse hosts; tomato, cucumber, and melon, indicated that densities remained at a low level during the winter, but increased steadily from February to March until migration into field crops in April. It is concluded that the control of the insect in greenhouse in winter and spring can play an important role for seasonal management of this pest in northern China.