Genetic variation in three Ceratocystis species with outcrossing,selfing and asexual reproductive strategies

Nuclear and mitochondrial markers were used to examine variation within three closely related species of tree pathogens with differing reproductive strategies. Ceratocystis eucalypti is obligately outcrossing; Ceratocystis virescens is capable of selfing due to unidirectional mating type switching; and Chalara australis is an asexual species, comprised of a single mating type. When the nuclear DNA fingerprinting markers (CAT)₅ and (CAG)₅ were used as probes against Pst I-restricted DNA, isolates of C. eucalypti were found to be highly polymorphic, and Ch. australis showed very little polymorphism. The selfing C. virescens showed an intermediate level of variation in the nuclear fingerprint markers, and much of the variation appeared to be due to differences between two forms of the species, one pathogenic to Acer and Liriodendron and another less-pathogenic form on Fagus and other hardwoods. Mitochondrial DNA (mtDNA) polymorphisms were examined by digesting total DNA with Hae III or CfoI, and C. eucalypti showed somewhat more variation in mtDNA than did C. virescens. The only polymorphism seen in the mtDNA of Ch. australis was associated with a plasmid. Selfing in C. virescens may be common and could explain an intermediate level of diversity when compared to the obligately outcrossing C. eucalypti and the asexual Ch. australis.     

In vitro evaluation of fungicides against Cylindrocladium spp. causing diseases of Eucalyptus in Kerala,India1

A total of 22 fungicides were evaluated in vitro for their efficacy against Cylindrocladium quinqueseptatum (CQ), C. ilicicola (CI), C. floridanum (CF), C. parvum (CP), and C. camelliae (CC) causing various diseases of Eucalyptus in Kerala, India. Though there were a number of fungicides effective (ED₁₀₀) in the comdial germination and poisoned food techniques, only carbendazim provided complete inhibition of CQ, CI and CC in the soil-fungicide screening technique; carbendazim was also highly effective against CF and CP. C. ilicicola appeared to be more tolerant than other species of Cylindrocladium as only a few fungicides were found to be effective against it even in the conidial germination technique. On comparison of the three fungicidal evaluation techniques, it is concluded that, for a pathogen producing microsclerotia, like Cylindrocladium, the soil-fungicide screening technique is the most appropriate one for obtaining reliable results.     

丽水市城区主要绿地植物病害调查初报

对丽水城区主要绿地植物病害进行了调查,结果表明：在117种园林绿化植物上,有园林植物病害151种,其中真菌病害143种、细菌病害2种、植原体病害1种、病毒病2种、生理性病害3种,危害较重或严重的病害46种。     

Performance of four <Emphasis Type="Italic">Trichogramma</Emphasis> species (Hymenoptera: Trichogrammatidae) as biocontrol agents of <Emphasis Type="Italic">Heliothis virescens</Emphasis> (Lepidoptera: Noctuidae) under various temperature regimes

Trichogramma spp. are major parasitoids of lepidopteran pest eggs, but there is large variation in efficacy toward a given pest among the numerous described Trichogramma species. It is important to select the Trichogramma species that most effectively parasitize and develop in target pest eggs for biological control. In this context, Trichogramma pretiosum, T. exiguum, T. atopovirilia and T. acacioi were studied in Heliothis virescens eggs under different thermal conditions. The parasitoids were reared at constant temperatures of 20, 25 and 30°C and tested at these respective temperatures, while parasitoids reared at 25°C were also tested at 20 and 30°C, for a total of 20 species–temperature combinations. About 30 H. virescens eggs were offered to the parasitoids for 24 h. Among the four species, parasitism rate by T. atopovirilia was highest at all temperature conditions, whereas T. acacioi had the lowest rates of parasitism at 25°C and 25/30°C. Parasitism ranged from 13.8 to 43.8% among all species–temperature combinations. Viability (emerged parasitoids) ranged from 80.8 to 98.4%, and was deemed satisfactory. The emergence rates of T. exiguum and T. acacioi were affected by temperature. Temperature also affected the sex ratio of T. exiguum at 25/30°C, whereas T. pretiosum and T. acacioi produced females predominantly independent of temperature. Overall, the parasitoid T. atopovirilia was the most efficient in parasitizing H. virescens eggs, though the levels of parasitism obtained might not ensure its successful use in biological control programs. The temperature-related differences in biological traits observed in the four Trichogramma species tested hint at the importance of making careful choices regarding climatic conditions where the parasitoid is going to be used when selecting a species for biological control programs.     

The impact of alley cropping Gliricidia sepium and Cassia spectabilis on upland rice and maize production

G. sepium and C. spectabilis hedgerows were established on slopes ranging from 18 to 31% in an effort to reduce soil erosion and improve upland rice and maize production. Upland rice and maize responded more to soil incorporated G. sepium biomass than to mulched, C. spectibilis. Incorporating hedgerow biomass equivalent to over 40 kg N per hectare, however, did not increase upland rice productivity. Maize, planted during the drought-prone second season, responded more than did rice to mulching. Crop performance improved along the slope gradient. Hedgerow-crop competition was observed at the upper and lower interfaces. Terracing intensified hedgerow-crop competition at the upper interface by reducing the crop's effective rooting depth. Under prevailing climatic and soil conditions, mixed hedgerows of C. spectabilis and G. sepium initially produced approximately 7 tons of fresh biomass per hectare every 3 months. Four years after hedgerow establihment, however C. spectabilis biomass was chlorotic and considerable mortality was observed, suggesting that C. spectabilis may be depleting soil N reserves.     

泡桐丛枝病类菌原体(MLO)病原传染长春花研究初报

菟丝子(Cuscuta spp.)是一种寄生植物,利用菟丝子为介体可以将植物病毒或类菌原体(mycoplasma like organism)从一株植物传染到另一株植物上。杨一朗陈景耀分别用大豆菟丝子和南方菟丝子为媒介成功地将甘薯丛枝病从甘薯传到长春花上,产生花器叶化、侧枝丛生病状。     

Opposite effects of different mineral oil treatments on <Emphasis Type="Italic">Macrosiphum euphorbiae</Emphasis> survival and fecundity

Mineral oil has been considered for several decades as an effective mean to control aphids and reduce the spread of non-persistent viruses. Mineral oil seems to reduce virus transmission efficiency interfering with the binding of the virions in the aphid stylets. However, several studies have shown the possible disruption of host selection process by mineral oil and some works have demonstrated a direct effect on the aphid vector. In this study the insecticidal properties of mineral oil (Finavestan EMA) alone against Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) were evaluated through the three main routes of exposure (topical contact, inhalation and ingestion). Results showed that no aphid survived after topical contact at oil concentrations ranging from 3 to 100% v/v. However, surprisingly, at a lower concentration (0.3%), survival was not affected but fecundity was enhanced. Moreover, exposure to oil volatiles enhanced aphid survival at the highest concentrations (30 and 100%) and daily fecundity at the lowest ones (0.3 and 3%). Delivered via artificial diet, mineral oil only affected aphid survival at the 0.3% concentration. This study demonstrates that mineral oil alone, regardless of a potential plant effect can induce either probiotic effects or toxic effects, depending on the mode of application and the concentration tested. These results can be of significance for the understanding of mineral oil properties in the fields.     

Fire fighting truck-based emergency mosquito biolarviciding to prevent outbreaks of malaria and arboviral disease in Kabul, Afghanistan

Emergency control of disease vectors requires high efficacy, rapid reaction and safe use of biocides in order interrupt transmission cycles without harming humans, non-target animals and the environment. In countries with complex emergencies, air-borne large-scale vector control is often limited, or impossible, due to questionable security as well as military, safety, equipment, or logistical constraints. While facing a potential outbreak of malaria and dengue fever in the Kabul area, Afghanistan, combined with high abundance of anopheline and Culex mosquitoes, emergency mosquito larvae control with Bacillus thuringiensis var. israelensis (Bti) and methoprene were carried out. For the first time, larvicides were applied by using a modern fire fighting truck in combination with aerial imaging of potential breeding sites. Three treatments with 0.07 g a.i. sterilized, water-dispersible granular (WDG) Bti/m² in combination with 0.0014 g a.i. methoprene/m², or 0.07 g a.i. Bti/m² alone, were conducted on July 29, August 29, and September 28, 2004, and significantly reduced larval indexes of 96.5 (P < 0.0001), 96.7 (P < 0.0001), and 97.6% (P < 0.0001) against anopheline, and 98.2 (P < 0.0001), 95.6 (P < 0.0001), and 96.2% (P < 0.0001) against Culex larvae, respectively. Before the larviciding campaigns started, up to 222.4 ± 32.0 mosquitoes were captured per standardized light trap per night. During May until October 2004, the following anopheline and Culex species were abundant: A. superpictus (29.3%), A. fluviatilis (17.0%), C. pipiens (15.2%), and C. pseudovishnui (38.5%). After biolarviciding, abundance of adult mosquitoes, as measured by light trap catches 20 days post-treatment, decreased significantly in Anopheles at 81.4 (P < 0.0001), 87.1 (P < 0.0001), and 78.2% (P = 0.01), and in part significantly in Culex for 75.2 (P < 0.0001), 78.3 (P < 0.0001), and 30.8% (P = 0.463), respectively. After the treatment, mosquito-associated annoyance complaints and disease transmission decreased markedly, and not a single confirmed case of malaria or arbovirosis was reported. It is concluded that biolarviciding using a fire fighting truck as the application device is a highly successful, rapid, and cost-effective method to control vector mosquito larvae, and to reduce human exposure to mosquito-borne diseases during complex emergency situations.     

Insecticidal activity of synthetic antioxidants,natural phytochemicals,and essential oils against an <Emphasis Type="Italic">Aspergillus</Emphasis> section <Emphasis Type="Italic">Flavi</Emphasis> vector (<Emphasis Type="Italic">Oryzaephilus surinamensis</Emphasis> L.) in microcosm

The purpose of this study is to investigate the insecticidal activity of two benzoic acids 2(3)-tert-butyl-4 hydroxyanisole (BHA) and 2,6-di(tert-butyl)-p-cresol (BHT); two phenolic acids 3-phenyl-2-propenoic acid (CA) and trans-4-hydroxy-3-methoxycinnamic acid (FA); and two essential oils of Eugenia caryophyllata (clove tree) and Thymus vulgaris (thyme) against Oryzaephilus surinamensis (L.) vector carrier of aflatoxigenic fungi on stored peanut. The weight loss of peanut, susceptibility of insects, Aspergillus isolation frequency from insects and peanut, and aflatoxin B₁ analyses from peanut were determined. BHA, BHT, and BHA/BHT mixture were highly effective against O. surinamensis, these chemical agents give 100% mortality at the doses assayed. Essential oil of thyme at 2,000 and 3,000 ppm were highly effective against O. surinamensis, these concentrations gave 100% mortality. No Aspergillus section Flavi contamination was observed in dead insects collected from peanut treated with BHA/BHT mixture. No differences were observed in the fresh weight of pods peanut among treatments with and without chemical agents. All samples of treated peanut pods showed complete inhibition of this toxin after 120 days of storage. Our results indicate that these substances could be evaluated further for the control of pest vectors of aflatoxigenic fungi of stored peanut.     

泡桐种源抗丛枝病性状的遗传变异

泡桐丛枝病是影响泡桐生长的一种主要病害，种源试验表明在毛泡桐种源中，除甘肃平凉未见发病以外，其它种源均有病害发生。江苏南京、湖北十堰、黄冈、陕西商县和辽宁大连5个种源发病较重，病情指数超过30％；白花泡桐丛枝病发病率较低，自然分布区南部的种源很少见到丛枝病发生，分布区北部与毛泡桐分布区有重叠的种源，丛枝病发病相对较重。毛泡桐起源靠西的种源发病较轻，随着经度的增加，丛枝病发病有增大趋势；白花泡桐发病与种源经度无关，而与纬度相关明显，呈现出纬度越高，发病率越低，病情指数越小的趋势。泡桐品种间丛枝病发病率和病情指数差异明显，通过品种选择可以获得抗病优良品种。     

Effects of trees on paddy bund on soil fertility and rice growth in Northeast Thailand

A study was conducted in Northeast Thailand on six rice paddy fields on a farm with similar soil (Aquic Quartzipsamments) and with a single tree on the paddy bund. There were 4 tree species: Parinarium anamense, Dipterocarpus obtusifolius, D. intricatus, and Samanea saman. Samples of soil (0–10 cm depth) and rice were collected at 3 positions (1, 5–7, and 9–11 m) away from the tree base in 3 replicated tree-soil trasects in each paddy field. Significantly higher pH, organic matter, and nutrients (N, P, K, Ca, and Mg) were found in paddy fields with S. saman (a legume tree) but grain yield and biomass of rice were significantly lower. Higher soil fertility was found in the positions closer to tree base while grain yields, biomass, and number of tillers were lower, and rice was taller and had more unfilled grain. Shading was deduced to be the key factor responsible for the depressed rice yields and growth at positions closer to tree base especially in the highly shading S. saman.     

A little-leaf disease of Eucalyptus in Kerala,India*

A little-leaf disease of Eucalyptus tereticornis, E. grandis and E. globulus characterized by stunting of plants and considerable reduction in size of leaves and internodes, was recorded during survey of nurseries and plantations in Kerala State. The survey indicated that though the little leaf disease was widespread, its incidence was quite low. Transmission of the symptoms by sap and graft techniques was unsuccessful. However, positive fluorescence and staining of phloem tissues by Dienes' stain indicates that this disease may be caused by mycoplasmalike organisms (MLO).     

Studies in Forest Pathology

A survey for the parasitic alga. Cephaleuros virescens Künze in relation to its seasonal distribution in different forest types has been done. The alga was absent in gymnosperms and was common in angiosperms. The disease severity was more in summer and the rainy season and absent in winter, Combretum decandrum was found to be most susceptible to this parasite alga. Altogether 49 hosts were recorded out of which 26 were new host records. Healthy leaves contain higher amounts of total nitrogen and total phenol, whereas in algal infected leaves the amounts of total sugar, total amino acid and dry weight were higher.     

Efficacy baselines of seven insecticides against larvae of Pandemis heparana (Lepidoptera: Tortricidae)

A diet-incorporation larval bioassay was used to evaluate the response of the leafroller Pandemis heparana (Denis and Schiffermüller) to seven insecticides: tebufenozide (Mimic 23% a.i., Bayer), methoxyfenozide (Prodigy 23% a.i., Bayer), flufenoxuron (Cascade 50 DC 4.7% a.i., BASF), lufenuron (Match 5.32% a.i., Syngenta), indoxacarb (Steward WG 30% a.i., Du Pont), abamectine (Vertimec EC 1.9% a.i., Syngenta) and spinosad (Laser 44.2% a.i., Dow Agro Science). Both neonate and 12-day-old (third to fourth instar) larvae were used in the bioassay. The obtained efficacy baselines were compared with the response of the pest exposed to leaves treated with the same insecticides. The persistence of field-aged leaf residues of the seven insecticides was bioassayed on neonate larvae. Given the obtained LC₅₀ values in the diet-incorporation bioassays larval age was not always a significant factor affecting the response of P. heparana larvae. Differences in LC₅₀ values between neonate and 12-day-old larvae were not statistically significant for abamectine, tebufenozide and methoxyfenozide. Young larvae seemed to be more susceptible than older larvae to spinosad, indoxacarb and lufenuron, while flufenoxuron was more effective against 12-day-old than neonate larvae. When the larvae were exposed to the insecticides on treated leaves, all the tested compounds were less effective on older larvae than on neonates. When applied at the recommended field rates, all seven insecticides can be considered highly effective against both neonate and 12-day-old larvae of P. heparana because their security index (SI = recommended field rate/LC₉₀) always exceeded the threshold value of 1. The high persistence of insect growth inhibitors (IGIs) and moulting accelerating compounds (MACs) in the field compensates for their relatively low SI values. For this reason and given their activity against Cydia pomonella, IGIs and MACs are the most interesting insecticides for spring treatments for the combined control of both species, P. heparana and C. pomonella.     

Varroa mites,viruses and bacteria incidences in Kenyan domesticated honeybee colonies

Varroa mite (Varroa destructor Anderson and Trueman) is a major global threat to the western honey bee (Apis mellifera L.). The ectoparasite has been implicated in the spread of honeybee viruses. Beekeeping plays a major role in transmission of the mite. The study aimed at assessing levels of Varroa infestation, bee viruses and bacteria incidences in domesticated honeybee colonies. Samples of adult honey bees, bee brood and Varroa mites were collected from Baringo, Narok, Kwale, Magarini, Voi, Ijara, Busia and Siaya in Kenya. Ten hives in each site were inspected for the presence of Varroa mites on adult bees using the icing sugar technique and forceps in sealed brood cells. The number of mites observed were recorded per site. Ribonucleic acid was extracted from the mites, brood and adult bees and a polymerase chain reaction was performed to detect the black queen cell virus. Pooled RNA samples of brood and adult bees were used in next generation sequencing on a 454 GS FLX platform to detect bee viruses and bacteria. Varroa mites were reported in all the study sites at varying levels. The black queen cell virus and three iflaviruses, European foul brood and its secondary causative agent Enterococcus faecalis were reported. The Kenyan honeybee population is threatened by bee pests and pathogens. There is a need for constant monitoring of bee pests and diseases in honeybee colonies in the country for early detection and to provide data on the status of bee health. All stakeholders in the beekeeping value chain should be enlightened on their role in pest and disease transmission.     

Climate tolerances of Philaenus spumarius should be considered in risk assessment of disease outbreaks related to Xylella fastidiosa

The bacterium Xylella fastidiosa (Xf) is an invasive insect-borne pathogen, which causes lethal diseases to important crops including olives, citrus, almonds and grapes as well as numerous forest, ornamental, and uncultivated plants. Outbreaks of Xf-related plant diseases are currently occurring in the Mediterranean region, causing substantial losses to various agricultural sectors. Several models have recently been published to identify which regions are at highest risk in Europe; however, such models did not consider the insect vectors, which constitute the key driver of short-range Xf spread. We fitted bioclimatic species distribution models to depict the macroclimatic preferences of the meadow spittlebug Philaenus spumarius L. (1978) (Hemiptera: Aphrophoridae), the major epidemiologically relevant vector currently responsible for Xf spread in the Europe. Many regions of Western Europe and Mediterranean basin are predicted by models as highly climatically suitable for this vector, including all regions where severe Xf have occurred so far. Conversely, the driest and warmest areas of the Mediterranean basin are predicted as little suitable for P. spumarius. Models forecast that agricultural-important parts of the southern Mediterranean area might experience a substantial decrease in climatic suitability for P. spumarius by the period 2040–2060. Areas predicted as highly suitable just for the bacterium but not optimal for this vector are apparently still free of severe Xf outbreaks, suggesting that climate tolerances of P. spumarius might partly explain the current spatial pattern of Xf outbreaks in Europe and should always be considered in further risk assessments.

     

The activity of some compounds extracts byAllium on stored-product insectsOryzaephilus surinamensis (L.),Sitophilus oryzae (L.) andTribolium castaneum (Herbst)

The bioactive metabolites of someAllium plants, all exhibiting interesting pharmacological activities, were tested for their attractive/repellent activity against saw-toothed grain beetle,Oryzaephilus surinamensis (L.), rice weevil,Sitophilus oryzae (L.), and rust-red flour beetle,Tribolium castaneum (Herbst), insects infesting the stored-products. The data obtained showed significant repellent effect of the thiosulfinates againstS. oryzae. Part 6 in the series “Chemistry of the genus Allium”.     

Viability retention of seeds of shisham (Dalbergia sissoo Roxb.) on the trees after maturity

In 1991 and 1992 studies on Dalbergia sissoo Roxb. showed the availability of ample amount of viable seed from November to May. Viability of seeds collected from December to March was more than 90 per cent. There was a slight but significant decrease in germination from March to may. Again germination per cent was slightly and significantly decreased from May to July. Thereafter, seed availability and viability were got drastically reduced. Sufficient viable seed of Dalbergia sissoo Roxb. can be collected at any time from November to July.