Evaluation of the biological control of the pink wax scale Ceroplastes rubens Maskell (Hom., Coccidae) with the introduced parasitoid Anicetus beneficus Ishii & Yasumatsu (Hym., Encyrtidae) in the Central province of Papua New Guinea

Abstract:  In order to evaluate the possibility of a classical biological control of the pink wax scale Ceroplastes rubens (Hom., Coccidae) with the parasitoid Anicetus beneficus (Hym., Encyrtidae), endemic parasitoids were collected (2000/2001) in three provinces in Papua New Guinea and parasitization levels were determined. Eight hymenopteran parasitoid species were identified: Aprostocetus sp. (Eulophidae), Coccophagus sp. (Aphelenidae), five Encyrtidae: Cheiloneurus sp., Coccidocnotus sp., Diversinervus sp., Metaphycus sp., Microterys sp. and Moranila sp. (Pteromalidae). Levels of parasitization were low, varying between 1.4 and 2.8%. A. beneficus was imported from Australia and 1100 specimens were released in spring 2002 at two locations with mango infested by C. rubens (Laloki and Tahira) in the Central Province . A. beneficus did establish at both sites. Six months after release, parasitization levels of C. rubens had increased from 2.8 to 5.9% (P  =  0.05) at Laloki and from 1.8 to 22.2% (P  =  0.01) at Tahira, with A. beneficus being the most frequent parasitoid (69% of all parasitoids). Workers of the ant genus Tapinoma (Dolichoderinae) were frequently collected from infested trees at Laloki, but were not present at Tahira. It is assumed that their presence is at least partly responsible for the lower degree of parasitization and number of A. beneficus at this site. The necessity of further studies is stressed.     

Induction of embryogenic mango cultures as affected by genotype,explanting, 2,4-D and embryogenic nurse culture

The nucellus was removed from immature seeds of 4 mango genotypes, andcultured under different induction conditions. The mango genotypes includedpolyembryonic ‘Hindi’ and ‘Nam Doc Mai’ and monoembryonic ‘Lippens’ and’Tommy Atkins‘. Nucellar explants were cultured on modified B5 basal mediumunder the following inductive conditions: 1) 4.52 μM 2,4-D; 2) nogrowth regulator (control); 3) 4.52 μM 2,4-D + embryogenic ‘Parris‘nurse culture; 4) no growth regulator + embryogenic ‘Parris’ nurse culture.Induction of embryogenic competence was mediated by 4 factors: genotype,explanting, 2,4-D and the presence of a highly embryogenic nurse culture,although there was considerable difference in genotype response. ‘Hindi’ hadthe greatest embryogenic potential, followed by ‘Lippens’, ‘Tommy Atkins‘and ‘Nam Doc Mai’, respectively. Induction of embryogenic cultures of allgenotypes at low frequency occurred as a result of explanting excisednucellus onto control medium. The most effective treatment for inducingembryogenic cultures was 2,4-D + embryogenic ‘Parris’ nurse culture with’Hindi’, ‘Lippens’ and ‘Nam doc Mai’, with the exception of ‘Tommy Atkins’,in which the treatment with 2,4-D alone was most effective. This revised version was published online in June 2006 with corrections to the Cover Date.     

Host–plant relationships and natural enemies of the invasive mealybug,Rastrococcus iceryoides Green in Kenya and Tanzania

The invasive mango mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae), believed to be native to southern Asia has rapidly invaded Kenya and Tanzania. A survey was carried out from February 2008 to July 2009 to study its geographical distribution, host–plant relationships and associated parasitoids in both countries. Our results infer that R. iceryoides is widely distributed across the coastal belts of both countries. Rastrococcus iceryoides was recorded from 29 cultivated and wild host plants from 16 families. Twenty‐one of these host plants are new records. Among the cultivated host plants, M. indica (407.68 ± 9.26/twig and 75.68 ± 7.13/leaf in Kibaha, and 595.86 ± 17.2/fruit in Kinondoni) and Cajanus cajan (L.) Millspaugh (18.15 ± 4.22/leaf and 233.62 ± 18.9/twig in Morogoro) recorded the highest levels of infestation. Parkinsonia aculeata (394.62 ± 11.7/twig, 0.15 ± 0.03/leaf and 8.44 ± 0.94/fruit in Kinango), Caesalpinia sepiaria Roxb. (3.33 ± 0.76/leaf and 155.81 ± 9.16/twig in Kinondoni) and Deinbollia borbonica Scheff. (2.70 ± 0.66/leaf and 112.65 ± 5.3/twig in Kibaha) were found to be the most heavily infested wild host plants. Six parasitoid species were recovered and are reported here for the first time to parasitize R. iceryoides. Anagyrus pseudococci Girault was the most dominant species accounting for 21% parasitism on M. indica and 20% parasitism on P. aculeata in Tanzania and Kenya, respectively. Despite this, the ability of the parasitoid to regulate the population of R. iceryoides was inadequate. Therefore, there is a need for foreign exploration and introduction of efficient coevolved natural enemies from its aboriginal home of southern Asia to minimize its impact on horticulture in Africa.     

Use of autochthonous lactic acid bacteria starters to ferment mango juice for promoting its probiotic roles

Strains of Leuconostoc mesenteroides, Pediococcus pentosaceus, and Lactobacillus brevis were identified from mango fruits by partial 16S rDNA gene sequence. Based on the ability of producing mannitol and diacetyl, Leuconostoc mesenteroides MPL18 and MPL39 were selected within the lactic acid bacteria isolates, and used as mixed starters to ferment mango juice (MJ). Both the autochthonous strains grew well in fermented mango juice (FMJ) and remained viable at 9.81 log cfu mL^?1 during 30 days of storage at 4°C. The content of total sugar of FMJ was lower than that of MJ, while the concentration of mannitol was higher than that of MJ, and the concentration of diacetyl was 3.29 ± 0.12 mg L^?1. Among detected organic acids including citric acid, gallic acid, lactic acid, and acetic acid, only citric acid and gallic acid were found in MJ, while all detected organic acids were found in FMJ. The concentration of lactic acid of FMJ was the highest (78.62 ± 13.66 mM) among all detected organic acids. The DPPH radical scavenging capacity of FMJ was higher than that of MJ. Total phenolic compounds were better preserved in FMJ. The acidity and sweetness had a noticeable impact on the overall acceptance of the treated sample.     

Novel Active Chrysanthemic Esters

The rates of recycling and turnover of glucose in 5-day- and 21-day-old lambs and adult sheep were measured by the method of single simultaneous injection of glucose-6-³H and glucose-6-¹⁴C. The ³H/¹⁴C ratio decreased linearly with time and was 0.58 and 0.60 in lambs of 5-day- and 21-day-old, respectively, and 0.82 in adult sheep at 120 min after injection of the labeled glucose. The pool size and turnover rate of glucose considerably decreased with age. The rate of glucose recycling was significantly higher in lambs of both ages (22.0 and 26.2%, respectively) than in adult sheep (11.1 %).     

Role of stressed mango host conditions in attraction of and colonization by the mango bark beetle Hypocryphalus mangiferae Stebbing (Coleoptera: Curculionidae: Scolytinae) and in the symptom development of quick decline of mango trees in Pakistan

The mango sudden death syndrome has become a serious threat to the mango industry and caused significant decline in mango production worldwide. The bark beetle Hypocryphalus mangiferae (Stebbing) (Coleoptera: Curculionidae: Scolytinae) has been suggested as a potential vector of the disease based primarily on field observations with little or no supporting empirical data. In this study, we investigated the role of infected mango trees in host attraction and colonization by H. mangiferae to determine if beetle attack and colonization contributes to the disease progression on mango trees. Initially, the role of various stress factors on beetle attraction and disease progression was assessed under lathe house conditions from 2008 to 2009. Results suggest that symptomatic or recently inoculated mango trees (without any obvious symptoms) are preferentially colonized by H. mangiferae. Although not significant, high numbers of beetles attacked stressed or wounded mango trees, compared to healthy or dead mango trees. Disease symptoms after beetle colonization, such as bark splitting, wilting and oozing, were further evaluated. These symptoms showed positive correlation with the degree of disease severity and host plant condition. Furthermore, two fungi, Ceratocystis fimbriata and Lasiodiplodia theobromae, were frequently isolated from the beetle and beetle-colonized trees. Based on these findings, they suggests that H. mangiferae can vector multiple fungi associated with mango sudden decline disease and play a significant role in outbreaks of this disease.     

Ethanolic extract of mango (Mangifera indica L.) malformed inflorescence as effective antifungal agent

Mango (Mangifera indica L.) suffers from floral and vegetative malformation and crop production is seriously affected. The anti-fungal activity of ethanolic extract of malformed mango inflorescence was observed at different concentrations (1000, 2000, 3000, 4000 and 5000 μl/ml) against 10 fungi, viz., Ustilago cynodontis, Cercospora cajani, Sphaerotheca sp., Cercospora sp., Alternaria solani, Bipolaris sp., Helminthosporium sp., Curvularia sp., Fusarium udum and Alternaria cajani. Spore germination of most of the fungi was inhibited at 5000 μg/ml. Some of them were also susceptible at 3000 or 4000 μg/ml concentration. Analysis of phenolic acids by high performance liquid chromatography (HPLC) showed 18 peaks in the extract, but only four could be identified, viz., capachin, gallic, benzoic and cinnamic acids. Because of the high efficacy of ethanolic extract of malformed mango inflorescence, its use under field conditions to control some plant diseases has been suggested.     

Multiline as a Strategy to Reduce Damage Caused by Colletotrichum lindemuthianum in Common Bean

The aim of the study was to verify whether a mixture of lines containing equal amounts of seven lines of Carioca‐type common bean, all agronomically uniform but each presenting different patterns of resistance to Colletotrichum lindemuthianum, would be less damaged by anthracnose than the individual pure lines. Plants cultured in experimental plots in Lavras, Minas Gerais, Brazil, in the dry harvest seasons of 2007 and 2008 were inoculated with a mixture of races 65, 81, 87, 89 and 337 of the pathogen, and the severity of anthracnose was evaluated at 10‐ day intervals commencing 12 days after inoculation. The progress of the disease was estimated from the coefficients of the linear regression equations (b₁) and from the areas under the disease progress curves (AUDPC). The mean grain yields were determined in both experimental periods. The value of b₁ for the multiline was not different from that presented by the resistant line MA‐II‐22 and indicated a slower progress of the disease over time compared with susceptible lines. There were no differences in AUDPC values between the multiline and the resistant lines. The multiline presented a grain yield that was similar to those of the most productive lines even though susceptible lines comprised more than 28% of the mixture and such lines showed the lowest yields of grain. It is concluded that the use of the mixture of lines represents a good strategy for reducing the progress of anthracnose in the field and, as a consequence, reducing loss of grain yield.     

热空气处理对杧果果实若干生理特性和贮藏效果的影响

采用紫花杧果为试材,以果实成熟季节的平均气温(30±2℃)为对照,研究35℃、38℃热空气分别处理24 h和48 h对果实生理生化特性和贮藏效果的影响。结果表明,与对照相比,温度升高或处理时间延长显著提高果皮MDA含量,抑制果实可溶性固形物含量的上升、可滴定酸的下降和果皮转黄,延缓果实的后熟过程。经38℃热空气24h和48h处理,病斑面积>50%的果实在第14天分别为45.8%和54.2%,果实发病率显著高于对照。而35℃热空气24h处理对上述指标的影响不明显。