Silver Leaf Research Articles

Habitat management strategies for the control of cereal stemborers and striga in maize in Kenya

Maize is the principal food and cash crop for millions of people in the predominantly mixed crop-livestock farming systems in Kenya. Stemborers and striga (Striga hermonthica) are major constraints to increased maize production in eastern Africa. An intercropping and trap crop system has been developed, using a ’push-pull’ strategy, for the control of stemborers in small scale maize farming systems. The ’push-pull’ strategy involves trapping stemborers on highly susceptible trap plants (pull) and driving them away from the crop using repellent intercrops (push). Napier grass (Pennisetum purpureum Schumach) and Sudan grass (Sorghum vulgare sudanense Stapf.) are used as trap plants, whereas molasses grass (Melinis minutiflora Beauv.) and two species of desmodium (Desmodium uncinatum Jacq. and Desmodium intortum Urb.) repel ovipositing stemborers. The integrated ’push-pull’ strategies were shown to increase parasitism of stemborers through attraction of parasitoids to one of the intercrops, molasses grass. The leguminous intercrop, silver leaf desmodium, drastically reduced damage to maize by the parasitic weed, striga. This aspect was further investigated and developed for integration **********w;th stemborer control. On-farm trials with farmers in Kenya have shown significant yield increases in maize farming.

Developmental Anatomy of Zucchini Leaves with Squash Silverleaf Disorder caused by the Silverleaf Whitefly

Squash silverleaf (SSL) is a physiological disorder of vegetables in the genus Cucurbita L. caused by feeding of nymphs of the silverleaf whitefly (SLW) (Bemisia argentifolii Bellows & Perring). SSL causes a silvering of the leaves and a blanching of fruit. Leaf silvering is caused by developmental separation of the upper epidermis and the palisade mesophyll layer resulting in additional air space and altered light reflection. The anatomical development of SSL was analyzed in young leaves of zucchini squash (Cucurbita pepo L.) using two susceptible genotypes (`Elite' and YSN347-PMR) and two tolerant genotypes (ZUC76-SLR and ZUC33-SLR/PMR). SLW nymphs were allowed to feed only on the mature leaves and the anatomy of the developing leaves was observed by light microscopy and transmission electron microscopy. Silvering began at the apex of young leaves and developed basipetally. The increased percentage of air space that resulted between the upper epidermis and palisade layers was the result of an increase in the duration of air space development in young, developing leaves. Chloroplasts in silvered tissue of mature leaves and in tissue of young leaves that later became silvered, were smaller and contained less starch than chloroplasts in tissue from noninfested plants. In contrast, development of genetic silvering, a condition not related to whitefly feeding, occurred throughout the entire leaf at one time, beginning as yellowed tissue in the axils of leaf veins then turning silver. Chloroplasts were normal in genetically silvered tissue of genotype YSN421-PMR. The SSL-tolerant genotype, ZUC76-SLR, did not show alteration in chloroplast structure or air space development when challenged with SLW; however, it had shorter and paler petioles, as did the susceptible genotypes. SSL symptoms were induced with spraying of gibberellic acid synthesis inhibitor chlormequat chloride in SSL-susceptible but not in SSL-tolerant genotypes. Reciprocal grafting between susceptible and tolerant plants showed that tolerance resides in the developing tissue and not the mature tissue on which the whiteflies feed.

DISTRIBUTION OF BEMISIA TABACI (HEMIPTERA: ALEYRODIDAE) BIOTYPES IN ITALY

AbstractEsterase banding patterns in native polyacrylamide gel electrophoresis, squash silver leaf (SSL) induction, and tomato yellow leaf curl begomovirus-Sardinia (TYLCV-Sar) transmission capability were investigated to evaluate variations among populations of Bemisia tabaci (Gennadius) from Italy and to relate their distribution to their geographic origin. Adults of the B biotype, adults of the Q-like biotype (which is similar to a Spanish biotype), and adults without esterase bands were found. The B biotype has been found in Italy since 1989. Two populations, including mainly B and Q-like biotypes, showed similar TYLCV-Sar transmission efficiency, independent of esterase banding pattern. Only populations from Liguria and Sardinia, which contained almost exclusively B-biotype individuals, were able to induce SSL. We observed that adults of the B biotype are widespread in greenhouses of northern Italy and Sardinia, whereas those of the Q-like biotype are present only in fields of southern Italy. These results suggest that the B biotype of B. tabaci was introduced into Italy likely while trading ornamental plants, whereas the Q-like biotype is native to the Mediterranean region.

The efficacy of indigenous and imported predators utilized in the biological control of Bemisia tabaci biotype „B” (Homoptera: Aleyrodidae) in greenhouse

The silver leaf whitefly,Bemisia tabaci biotype „B ”(Homoptera:Aleyrodidae)is one of the most serious vegetable and ornamental plants pest in Egypt.Predators play an important role in controlling this species. The present work deals with the abundance of indigenous predators in greenhouse on three host plants mostly of vegetable crops during April –July,1996.Chrysoperla carnea (Stephens)(Neuropteran: Chrysopidae)is considered the most abundant predator acting on Bemisia. In the meantime,the work deals also with the potential of the imported predators,namely Delphastus pusillus Le Conte (Coleoptera:Coccinellidae)and Macrophillus caliginosus (Wagner)(Hemip- tera :Miridae).These predators were released 3 times on eggplant (Solanum melongena)and at the ratio of 1 individual and 2 individuals/plant for D.pusillus and M.caliginosus,respectively.Results indicate that predators increased in numbers while whitefly population decreased in comparison to control homologues. Biotype B.tabaci was identified in John Inn...

THE TECHNIQUE OF GOTHIC ALTARPIECES ON SPAIN’S MEDITERRANEAN COAST

"THE TECHNIQUE OF GOTHIC ALTARPIECES ON SPAIN’S MEDITERRANEAN COAST." Studies in Conservation, 43(sup2), p. 4

Late mediaeval wall painting techniques at Farleigh Hungerford Castle and their context

Little systematic analysis has been undertaken of late mediaeval wall painting in England, but the early fifteenth-century paintings at Farleigh Hungerford have recently been subjected to detailed examination. Despite previous invasive conservation treatments, this revealed a highly sophisticated use of translucent glazes over gold and silver leaf, a wide range of pigments including orpiment and lead-tin yellow, and oil as a medium. These materials, the techniques of their application and aspects of their alteration in situ are considered within the context of other English wall painting of the period, as well as the sophistication of the scheme attributed to the patronage of Sir Walter Hungerford.

Comparison of Silverleaf Whitefly-Induced and Chlormequat Chloride-Induced Leaf Silvering inCucurbita pepo

Whitefly-mediated squash silverleaf is induced by the feeding of nymphs of the silverleaf whitefly, Bemisia argentifolii, but the mechanism involved in symptom expression is unknown. Several plant biochemical regulators were tested to determine whether they could mitigate expression of squash silverleaf in Cucurbita pepo. Application of chlormequat chloride, a gibberellic acid biosynthesis inhibitor, induced leaf silvering symptoms similar to those induced by the silverleaf whitefly in squash plants, cvs. Senator and Dixie, but not in cv. Small Sugar Pumpkin. Chlormequat chloride-induced silvering never extended over more than 80% of the upper leaf surface, compared with 100% for whitefly-induced silverleaf. Paclobutrazol, but not Alar, also produced leaf silvering symptoms. Chlormequat chloride treatment also resulted in internodal stem shortening, increased chlorophyll levels, and increased root and stem weight in Small Sugar Pumpkin and Senator but not in Dixie. Chlormequat chloride did not produce detectable double-stranded RNAs (dsRNAs) or changes in intercellular fluid proteins in any of the C. pepo cultivars tested. Silvered leaves from whitefly-infested plants, in contrast, had 15 to 40% lower chlorophyll levels, two induced intercellular leaf proteins, and some reductions in foliar and root biomass. No dsRNAs were detected in whitefly-silvered tissues or plants. Gibberellic acid applied after chlormequat chloride or paclobutrazol treatment resulted in less internodal shortening and decreased both chemical- and whitefly-induced leaf silvering. Chlormequat chloride-treated plants attracted greater whitefly oviposition and had more nymphs than untreated controls in greenhouse tests. These data suggest that leaf silvering induced by gibberellic acid biosynthesis inhibitors and by the silverleaf whitefly results from hormonally mediated alterations in the plant's physiology. Because the silverleaf whitefly also induces discoloration disorders in plants other than squash, hormonal inhibition may be a general component of whitefly phytotoxicity.

Effects of Incubation Time and Temperature on In Vitro Selective Delignification of Silver Leaf Oak by Ganoderma colossum

The effects of incubation time and temperature on the ability of isolates of the chlamydosporic and thermophilic fungus Ganoderma colossum (Fr.) C. F. Baker to cause selective delignification of Quercus hypoleucoides A. Camus were evaluated by standard in vitro agar block tests. Chemical and scanning electron microscopy studies of decayed wood were used to determine the extent of selective delignification or simultaneous decay caused by each fungal isolate. At 35 deg C, the percent weight loss increased from 6.1% after 4 weeks to a maximum of 32.5 to 33.0% after 16 and 20 weeks of incubation. The average percent Klason lignin-chlorite holocellulose ratios (PKL/CHC) decreased from 0.35 in the control wood block to 0.22 in wood blocks incubated for 12 weeks; this indicated selective delignification. The average PKL/CHC increased for the 16- and 20-week incubation periods, indicating greater removal of polysaccharides during longer incubation periods. In temperature studies, the percent weight loss after 12 weeks was 26 to 27% between 30 and 40 deg C and less than 16% for the 25 and 45 deg C treatments. The average PKL/CHC ranged from 0.18 to 0.16 between 35 and 40 deg C, whereas they were 0.23 and 0.31 for the 25 and 45 deg C treatments, respectively. Scanning electron microscopy confirmed an optimum temperature range near 35 to 40 deg C and incubation times of 8 to 12 weeks for selective delignification. Under these conditions, ray parenchyma, fiber tracheids, and vessels were devoid of middle lamella; pit regions of cells were visible with significantly enlarged apertures; and individual cells were separated and clearly delimited. Extensive delignification of wood occurred throughout the wood blocks evaluated. Incubation times longer than 12 weeks resulted in greater degradation of wood cell walls and thus in greater removal of the polysaccharide component of the wood. For incubation times of 4 weeks or a temperature of 25 deg C, limited to no degradation of cells was observed. At 45 deg C, walls of fiber tracheids were eroded and ray parenchymal cells were extensively degraded, indicating that simultaneous degradation of cell walls occurred. Thus, the incubation temperature influenced the type of decay by G. colossum observed on oak wood blocks: extensive selective delignification at 35 to 40 deg C after more than 8 weeks of incubation or simultaneous decay at 45 deg C with 14% weight loss after 12 weeks of incubation. Isolates of G. colossum may prove useful in studies on mechanisms of delignification and biotechnological applications (e.g., biopulping) of lignin-degrading fungi.

The diet and feeding behavior of the silver leaf monkey (Trachypithecus auratus sondaicus) in Indonesia

I describe the diet and feeding behavior of silver leaf monkeys (Trachypithecus auratus sondaicus) in the Pangandaran Nature Reserve, West Java, Indonesia, and compare a group living in old secondary rain forest with a group living in mixed plantation/secondary forest to determine intraspecific variation in feeding behavior and the importance of the plantation species in the diet of the monkeys. Young leaves and leaf buds made up slightly less than half of their diets, with both groups showing a preference for a few species when seasonally available. Fruits and flowers of a few species were also preferentially selected when available. These included sweet, fleshy fruits, which most other colobines tend to avoid. Young leaf intake was greatest in months when fruit intake was low. Mature leaves were rarely eaten. Both groups spent approximately 20% of feeding time foraging on Moraceae species. Differences in the diet of the two groups were related largely to differences in vegetational composition and the availability and abundance of food items for the species common to both sites. Teak (Tectona grandis) was the top food species of the group living in mixed plantation/secondary forest, with the midribs of young leaves preferentially selected. Young leaves ofT. grandis, available throughout the study, provided a staple food and were eaten when preferred foods were scarce. More favored food items were available to the group living in old secondary forest, though none was a staple food.

Plant Population Influence on Squash Yield, Sweetpotato Whitefly, Squash Silverleaf, and Zucchini Yellow Mosaic

Zucchini squash (Cucurbita pepo L.) fruit yield and the incidence of sweetpotato whitefly (SPWF) [Bemisia tabaci (Gennadius)], squash silver leaf (SSL) disorder, and zucchini yellow mosaic virus (ZYMV) were measured during Spring and Fall 1991 in experiments containing various plant populations. In both experiments, as the within-row spacing increased from 30.5 to 76.2 cm or the number of plants per hill decreased from three to one, the number of marketable fruit per hectare decreased, and the marketable fruit per plant increased. Adult SPWF populations increased with decreased within-row spacing in the spring but not the fall experiment. The incidence of SSL or ZYMV infection was not affected by plant population in either experiment. The results indicate that increasing zucchini squash plant population can increase yield without affecting the incidence of SSL or ZYMV.

Differential Susceptibility to Leaf Silvering in Cucurbita pepo

`Striato d'Italia' (cocozelle group) and `Clarita' (vegetable marrow group) summer squash were grown in the greenhouse and field in the presence of sweetpotato whiteflies (Bemisia tabaci Germ.) and their susceptibility to leaf silvering was compared. Silvering was less severe in `Striato d'Italia' in the greenhouse and field.

Sweetpotato Whitefly, Drought Stress, and Leaf Silvering of Squash

Summer squash (Cucurbita pepo L.) plants were grown in pots with high (290% capacity) or low (45% to 70% of capacity) soil moisture. The plants were exposed or not exposed to sweetpotato whiteflies (Bemisia tabaci Genn.). Only the plants exposed to whiteflies developed leaf silvering. Silvering was more severe in plants subjected to low soil moisture.

Susceptibility to leaf silvering in the cultivar groups of summer squash

Summer squash (Cucurbita pepo) cultivars, three from each of the six cultivar groups, were grown under field and greenhouse conditions at Fort Pierce, Florida, U.S.A. in the presence of sweetpotato whiteflies (Bemisia tabaci) and observed for severity of leaf silvering. All cultivars were affected by leaf silvering, but some had less severe symptoms than others. The cocozelle group was the least susceptible to silvering. There appeared to be an association between geographic origin of cultivars and their susceptibility to silvering.

Influence of Endosulfan Sprays and Aluminum Mulch on Sweetpotato Whitefly Disorders of Zucchini Squash and Tomatoes

Sweetpotato whitefly (Bemisia tabaci Gennadius) (SPWF) is a major pest throughout the southern USA. It is associated with the economically important disorders tomato irregular ripening (TIR) and squash silver leaf (SSL). Two possible components of SPWF management are the insecticide endosulfan (6,7,8,10,10-hexachloro-1,5,5a,6,9,9a-hexahyde-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) and aluminum reflective mulch. This study was conducted to determine the effect of these control procedures, separately or in combination, on SPWF populations, the TIR and SSL disorders, fruit quality, and fruit yield of tomatoes (Lycopersicon esculentum Mill.) and zucchini squash (Cucurbita pepo L.). These parameters were evaluated in field plots during both the spring and fall of 1990. Tomato fruit yield increased (13 000 to 39 000 lb/acre), culls decreased (45 to 7%), and the percentage of TIR fruit decreased (52 to 22%) in the spring experiment as a result of endosulfan spray applications. Endosulfan sprays had no detectable effect on tomato fruit quality or yield in the fall experiment, and aluminum reflective mulch had no effect during either season. Zucchini squash yields were not affected by aluminum reflective mulch or weekly endosulfan spray applications in either experiment. Endosulfan reduced the percentage of plants with symptoms of squash SSL from 54 to 22% in the spring experiment. No SSL occurred in the fall planting. The increase in SPWF population in the squash and tomato plots was not affected by the aluminum reflective mulch or endosulfan sprays during either season. Our data suggest that environmental or physiological factors in combination with SPWF influence the incidence of SSL on squash and TIR on tomatoes. Research Question Sweetpotato whitefly (Bemisia tabaci Gennadius) can cause damage on squash (Cucurbita pepo L.) and tomatoes (Lycopersicon esculentum Mill.) by both direct feeding and the viruses it transmits. This study compares the influence of endosulfan (6,7,8,10,10-hexachloro-1,5,5a,6,9,9a-hexahyde-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) sprays and reflective aluminum mulch on whitefly populations and the whitefly-induced disorders squash silver leaf and tomato irregular ripening. Literature Summary Several insecticides, including endosulfan, are known to reduce sweetpotato whitefly populations. Various colored mulches, including aluminum, also have been shown to reduce whitefly populations. Study Description Tomatoes and zucchini squash were grown in the field in the spring and fall of 1990 in Ft. Pierce, FL. Each of the plantings was divided into plots, which were treated with a weekly spray application of endosulfan, aluminum reflective mulch, both endosulfan and aluminum mulch, or neither endosulfan nor aluminum mulch. Sweetpotato whitefly populations, the incidence of tomato irregular ripening and squash silver leaf, and tomato and squash yields were monitored throughout the growing season. Applied Question Do endosulfan sprays and/or aluminum reflective mulch influence tomato or squash yields, tomato irregular ripening or squash silver leaf, or sweetpotato whitefly populations? Tomato yields were significantly increased in plots with weekly applications of endosulfan in the spring experiment, but not the fall experiment. The percentage of tomato irregular ripening also was reduced significantly by the endosulfan spray treatments in the spring experiment. Marketable squash yields were not affected by any of the treatments. In the spring experiment, however, weekly endosulfan spray applications reduced squash silver leaf symptoms. There were no significant differences in the mean weekly adult sweetpotato whitefly populations for any of the treatments in either the spring or fall experiments. In addition, aluminum painted mulch had no effect on tomato or squash yields, fruit quality, sweetpotato whitefly induced diseases, or adult sweetpotato whitefly populations. Table 1. Influence of endosulfan sprays and aluminum reflective mulch on tomato and squash yields, tomato irregular ripening and squash silver leaf, and sweetpotato whitefly populations. Tomatoes* Squash* Spring Fall Spring Fall Treatment Yield† TIR SPWF Yield† TIR SPWF Yield† SSL SPWF Yield† SSL SPWF Endosulfan + + - - - - - - - - NA - Reflective mulch - - - - - - - - - - NA - Endosulfan plus + + - - - - - + - - NA - reflective mulch * A plus sign indicates that the yield or incidence was significantly greater (P = 0.05%) than that of the untreated control. A minus sign indicates the yield or incidence was not significantly greater. NA indicates no squash silver leaf was present in the plots. † Yield was measured in both number and weight of marketable fruit per acre.

Evaluation of Spunbonded Polyethylene Row Covers as a Method of Excluding Insects and Viruses Affecting Fall-Grown Squash in Florida

A lightweight floating row cover, used alone and in combination with a white-on-black polyethylene mulch, was evaluated under the hot, humid conditions of the fall growing season in Florida as a method of controlling aphid-borne mosaic viruses, whitefly-induced leaf silvering, and insects directly damaging zucchini squash. Yields increased dramatically with the use of covers, especially if covers were left in place for at least 1wk after plants began to bloom. Covers excluded pickleworm, Diaphania nitidalis (Stoll); melonworm, Diaphania hyalinata (L.); sweetpotato whitefly, Bemisia tabaci (Gennadius), and several colonizing aphid species. Except for B. tabaci, insects colonized newly uncovered plants slowly, remaining at low densities for up to 2 wk after removal of covers. Few winged aphids landed in water pan traps placed over covers, which may explain why aphids and aphid-vectored viruses remained at low levels even when covers were torn. Incidence of potyviruses and silverleaf was greatly reduced by use of row covers, but symptoms of viral infection developed 1-2 wk after removal. If used over an entire planting, high levels of inoculum presumably would not develop, and viral infection might be delayed even longer.

COLORED GLAZES ON SILVER-GILDED SURFACES

AbstractColored glazes derived from vegetable and animal sources and applied over silver leaf have been used in many eras and regions of the world to adorn sculpture and decorative art objects. Examples from Latin America during the Viceregal period are examined and compared, with reference to literature sources and to FTIR analysis. Attention is drawn to the use of native American materials in some instances, such as the varnish of Pasto, Colombia, and the lacquer of Patzcuaro, Mexico.

CONSERVATION OF THE ARCHITECTURAL DECORATION OF MISSION SAN XAVIER DEL BAC, TUCSON, ARIZONA

The Mission of San Xavier del Bac, located seven miles south of Thcson, Arizona, on the San Xavier Tohono O'odham (Papago) Indian Reservation, is considered to be the finest example of Spanish colonial architecture in the United States. The interior of the church is almost entirely decorated in a late Mexican baroque style, comprising wall paintings as well as polychromed and gilded sculptural and architectural elements. Dating from the late eighteenth century, this·decoration is of a very high standard and is surprisingly intact. The mission ~hurch is a living monument, served daily by Franciscan fathers whose order constructed the present church c .1778-97, with the help of the indigenous Tohono O'odham Indians. The east transept chapel of 'La Madre Dolorosa' (Sorrowing Mother) contains polychromed architectural relief work and wall paintings. The latter portray La Nuestra Senora del Rosario (Our Lady of the Rosary), La Virgen Nitla (The Young Virgin Mary), and mourning figures of the Sorrowing Mother and St John the Evangelist on either side ofthe central Crucifixion. The niches and oval medallions contain relief and free-standing sculptures of Franciscan saints. The wall paintings are executed on a very fine buff-coloured and water-sensitive preparation layer applied over a lime-sand plaster. The pigments have been applied a secco with an aqueous tempera binder which is fairly sensitive to moisture. The relief decoration is composed of painted plaster moldings and cornices, th~ finest of which is the highly ornate frame of the central crucifix which consists of a stylized floral band and scalloped channels coloured with transparent glazes applied over metallic leaf. Examination of cross:-sectional samples taken from this area reveals the following stratigraphy: lime-sand stucco overlaid with two gesso preparation layers, a coarse layer covered by a finer one, both containing calcium sulphate anhydrite. Madder lake and copper resinate glazes have been applied over silver leaf on a red coloured bole. This has been overlaid with a 61i-thick varnish layer. In addition to natural earths, the pigments employed in the wall decoration include: Prussian blue, vermilion and orpiment. Although there is some minor evidence of rising damp and hygroscopic salts,. except for the areas where it is clear that there have been infiltrations of rainwater in the past (the vault), moisture does not seem to have been a major agent. of deterioration. Extremely low relative humidity, .high temperature fluctuations and high natural' and ultraviolet light levels appear to be the primary causes of the localized detachment of the painted and relief decoration. The original polychromy is largely obscured by thick layers of dust, candle soot, and bird and bat excrement as well as by the hardened nests of mud dauber wasps (Sceliphron caementarium) . During some previous effort at restoration, possibly early in the twentieth century, a fixatiye was liberally applied to the surfaces. The intention seems to have been to revitalize the original colours. The fixative, which appears to have:darkened and turned orangebrown, encouraged contraction of the paint and preparatory layers at low levels of relative humidity and resulted in the separation of these layers from their support. Analysis of the fixative using Fourier transform infrared analysis shows that it is a n.atural tree resin, possibly from the plesquite tree (Prosopis juliflora). Very unsightly filling oflacunae,'oone in 1968, is evident in the scene of the Virgen Nina. The incompatible filling material, which

Food selection by the silver leaf monkey,Trachypithecus auratus sondaicus, in relation to plant chemistry.

Samples of leaves and fruits exploited as food items byTrachypithecus auratus sondaicus were analysed for nitrogen content, acid detergent fibre (ADF), pepsin cellulase digestibility (CDIG), condensed tannins (CT), total phenolics (TP) and protein precipitation capacity (PP) and compared with fruits and leaves not eaten. Differences in chemical measures for items eaten and not eaten were not statistically significant but trends indicate that leaves may have been selected for their lower fibre content and greater digestibility. Fruits eaten also had a higher mean level of CDIG and lower mean level of ADF than fruits not eaten but these measures are not considered to be of major importance in fruit selection as CDIG was lower and ADF higher in fruits eaten than in leaves eaten. Levels of CT, TP and PP capacity were higher in fruits eaten than in fruits not eaten but lower in leaves eaten than in leaves not eaten. The role of tannins and phenolics in food selection is discussed. Leaves (and fruits) were not strongly selected on the basis of protein content. Approximately half the dietary intake ofT. auratus sondaicus was leaves, a protein-rich food source. Possibly, protein levels in foliage at Pangandaran were sufficient that selection for this nutrient was not required. A nutrient other than protein (for example, soluble carbohydrates) may have been maximised through food selection. The protein/ADF ratio may provide an indicator of the acceptability of foliage in a habitat as potential food for a colobine. However, this ratio did not govern food selection byT. auratus sondaicus at Pangandaran.

Isolation and identification of two new metabolites from silver leaf fungus Stereum purpureum

Two new sterpurene sesquiterpenes have been isolated from Stereum purpureum and identified as 4,12-dihydroxysterpurene (1) and 5,12-dihydroxysterpurene (3) mainly on the basis of mass spectra and extensive nuclear magnetic resonance spectrometry of compounds 1 and 3 and their diacetate derivatives 2 and 4

Characteristics of Sweetpotato Whitefly-Mediated Silverleaf Syndrome and Associated Double-Stranded RNA in Squash

A 48-h feeding by 20 adult sweetpotato whiteflies (SPWF), Bemisia tabaci, resulted in 100% (63/63) of the squash (Cucurbita pepo Dixie) plants showing vein clearing and/or leaf silvering. No vein clearing and/or leaf silvering was apparent in squash plants exposed to SPWF for 8 h or less. The ability to mediate silverleaf symptoms was correlated with the density of SPWF. The percentage of plants that exhibited leaf silvering after 48-h feeding by 2, 5, 10, and 20 SPWF were 0, 13, 84, and 100%, respectively (...)