Calcium silicate enhances resistance of sugarcane to the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae)

Abstract

• 1 The stalk borer Eldana saccharina is the most destructive pest in sugarcane in South Africa. This study investigated: (1) the potential of applied silicon in enhancing plant resistance of sugarcane to E. saccharina, using calcium silicate as a carrier; (2) whether there was any interaction between cane variety (and stalk borer resistance) and silicon treatment.
• 2 Six commercial varieties of sugarcane were treated in a pot‐plant trial with two levels (5000 and 10 000 kg/ha) of calcium silicate. After artificial infestation with E. saccharina, response to the treatments was assessed in terms of borer numbers and mass, and stalk damage.
• 3 Calcium silicate significantly enhanced resistance at the higher rate compared with the control. Borer mass was reduced by 19.8% and stalk length bored by 24.4%. Lower treatment values were intermediate between those of the higher treatment and the control.
• 4 The interaction between variety and Si treatment was not significant when varieties were examined individually in the analysis. However, the interaction was significant for borer mass when varieties were grouped according to their resistance characteristics. Susceptible varieties might benefit more from treatment with silicon than resistant ones, as resistant varieties showed no significant effect of silicon.
• 5 All varieties had increased silicon content due to the treatments, but differed appreciably in stalk silicon content at the different treatment levels. Similarly, within varieties, stalk silicon content did not correspond consistently with borer response patterns and silicate application rates.

     

The Ability of Coptera haywardi (Ogloblin) (Hymenoptera: Diapriidae) to Locate and Attack the Pupae of the Mediterranean Fruit Fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), under Seminatural Conditions

In Latin America, the diapriid Coptera haywardi (Ogloblin) attacks the pupae of tephritid fruit flies. Anastrepha spp. are among its natural hosts, but in the laboratory it also develops in the exotic Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Field cage tests demonstrated that C. haywardi could locate and parasitize Mediterranean fruit fly pupae under seminatural conditions as found in a Guatemalan coffee plantation. A mean of 18.3% of the pupae buried artificially at depths of 5 mm were parasitized by C. haywardi, while those buried at 15 mm suffered 3.2% parasitism. In a laboratory experiment, larvae that buried themselves to pupate were not significantly more likely to be parasitized than artificially buried pupae, although they may have left a physical or chemical trail that betrayed their presence. Thus, the artificial burial of pupae is unlikely to grossly underestimate C. haywardi efficacy in the field. Another field cage test found that mortality levels due to unsuccessful parasitoid attacks were similar to those resulting from successful parasitism. Thus, the actual effect of a mass-release might be considerably greater than that suggested from parasitism data alone. The results are considered sufficiently positive to encourage further testing of C. haywardi as a biological control agent of the Mediterranean fruit fly.     

Feeding Life Style of Redlegged Earth Mite, Halotydeus Destructor (Acari: Penthaleidae), in pastures and the role of broad-leafed weeds

Redlegged earth mite, Halotydeus destructor, is a major pest of pastures and crops in Australia, and also feeds on lower plants on the soil surface. Feeding behaviour is reviewed, and the role of Arctotheca calendula, capeweed, in determining occurrence and abundance in pastures is investigated. Mites fed more and produced more progeny on Trifolium subterraneum (subclover) than on capeweed in non-choice experiments. In pastures with mixed species three times more mites were feeding on subclover than on capeweed foliage. However, twice as many mites were found on the soil surface under pasture patches consisting mainly of capeweed than of subclover. Patches were selected on the basis of pasture height, irrespective of plant composition. Twice as many mites were found in populations under patches of tall than short pasture. The daytime relative humidity was higher in tall than short patches, and the temperature slightly lower, making tall patches a more favourable niche for these mites. Ninety per cent of H. destructor were on the soil surface, while 10% were feeding on the upper canopy of pasture. The proportion of each population that was feeding was greater on subclover than capeweed, and subclover was a more suitable food. In Australia H. destructor occurs in regions with mixed pasture species, grown in rotation with grain crops. The ability of H. destructor to utilize foliage of a range of plant species of differing suitability for food, while living mostly on the soil surface in niches favourable for survival, has enabled it to become very abundant.     

Characterization of Farmer’s knowledge and management practices of papaya mealybug Paracoccus magnatus (Hemiptera: Pseudococcidae) in Tanzania

Papaya mealybug (PMB) is a serious insect pest for papaya production in Sub-Saharan Africa, limiting production potential in farming communities. We did a household survey to evaluate the Characteristics of farmers' knowledge, challenges, and current (PMB) control practices in four papaya growing regions of Tanzania namely, Tanga, Dodoma, Pwani, and Katavi involving 100 papaya farmers. The study found that 96% of farmers reported PMB, as a major challenge in papaya production. Very few (0.8%) of the farmers were knowledgeable on insect pest identification. Chemical pesticides were the only option for PMB control, and 43.0% of farmers were able to access and apply. We also found that 36.4% of the farmers were aware of the adverse effects of chemical pesticides. Furthermore, the study observed that 0.3% of farmers use botanical pesticides. Additionally, the study observed that 44.1% of farmers use control measures against PMB, the remaining 55.9% did not practice any control measure, thus leading to low papaya yields observed in the study regions. Our findings provide insights to farmers into the use of plant-based pesticides, mainly plant essential oils, and its benefits that may promote farmers' attitudes towards increasing papaya yield and reducing chemical pesticide use to avoid pest resistance.     

储粮环境挥发性化合物与储粮害虫的关系研究进展

每种粮食的储粮环境中都存在有其特征性挥发物,储粮害虫的发生对储粮环境中挥发物具有重要影响。本文简述了顶空式固相微萃取法、浸入式固相微萃取法、电子鼻检测法等储粮挥发物的提取方法及其优缺点,对小麦 Triticum aestivum L.、稻谷 Olyza sativa L.、玉米 Zea mays L.和燕麦 Avena sativa L.等主要储藏粮食种类的挥发性化合物成分、粮食挥发物对昆虫行为反应的影响、主要储粮害虫(赤拟谷盗 Tribolium castaneum、锈赤扁谷盗 Cryptolestes ferrugineus 和象虫 Sitophilus spp.)发生与粮食挥发物的关系等研究进展进行综述,探讨了储粮环境挥发性化合物与储粮害虫关系未来的研究方向,以期对今后储粮害虫生态防治研究与应用提供参考信息。     

Isolation and characterization of microsatellite loci in the two‐spotted spider mite,Tetranychus urticae (Acari: Tetranychidae)

Sixteen microsatellite loci are described for the two‐spotted spider mite Tetranychus urticae, which is an agricultural pest. The microsatellite loci were obtained through the construction of an enriched library; these loci exhibited polymorphisms (2–5 alleles per locus) and high levels of observed (0.033–0.667, average 0.415) and expected (0.033–0.602, average 0.336) heterozygosities. The isolated microsatellite markers are expected to be useful for the construction of a linkage map of this species.     

Network analysis for co‐occurrence of pest insects on host crops

In this study, the co‐occurrence patterns of 618 pest insects for 47 host crops, including vegetables, grains, and fruits, were identified. To identify the pest co‐occurrence patterns for various crops, and the interactions among the pest insects and crops, we employed social network analysis methods. We used three traditional centrality measures (degree, closeness, and eigenvector) to determine the relative significance of each crop and pest as a node in the network. Throughout the network analysis, crops and pest nodes were divided into six groups, based on modularity. Crops in the same group could be considered as alternate hosts for pests from the same group. There were clear differences in the cultural practices between groups (i.e., dryland farming versus wetland farming). This indicated that dryland crop pests do not use wetland crops as resources. Pome fruit trees, such as apple and pear, had high centrality indices, which indicated the importance of these crops in the network and their high vulnerability to damage by a multitude of pests. In this study, although it was assumed that all crops were cultivated on the same piece of land during a single growing season, the complex interactions between the whole units were visualized and analyzed as a computable network.     

A high‐quality chromosome‐level genome assembly of a generalist herbivore,Trichoplusia ni

The cabbage looper, Trichoplusia ni, is a globally distributed highly polyphagous herbivore and an important agricultural pest. T. ni has evolved resistance to various chemical insecticides, and is one of the only two insect species that have evolved resistance to the biopesticide Bacillus thuringiensis (Bt) in agricultural systems and has been selected for resistance to baculovirus infections. We report a 333‐Mb high‐quality T. ni genome assembly, which has N50 lengths of scaffolds and contigs of 4.6 Mb and 140 Kb, respectively, and contains 14,384 protein‐coding genes. High‐density genetic maps were constructed to anchor 305 Mb (91.7%) of the assembly to 31 chromosomes. Comparative genomic analysis of T. ni with Bombyx mori showed enrichment of tandemly duplicated genes in T. ni in families involved in detoxification and digestion, consistent with the broad host range of T. ni. High levels of genome synteny were found between T. ni and other sequenced lepidopterans. However, genome synteny analysis of T. ni and the T. ni derived cell line High Five (Hi5) indicated extensive genome rearrangements in the cell line. These results provided the first genomic evidence revealing the high instability of chromosomes in lepidopteran cell lines known from karyotypic observations. The high‐quality T. ni genome sequence provides a valuable resource for research in a broad range of areas including fundamental insect biology, insect‐plant interactions and co‐evolution, mechanisms and evolution of insect resistance to chemical and biological pesticides, and technology development for insect pest management.     

入境台湾蔬菜有害生物口岸检疫

【目的】了解台湾蔬菜有害生物的入境风险,阐明加强口岸检验检疫的对策措施。【方法】对全国口岸2014—2019年6月台湾新鲜蔬菜和蔬菜种子的入境口岸、截获的有害生物及寄主情况进行统计和分析。【结果】入境台湾新鲜蔬菜仅有3批次,均没有截获疫情。入境台湾蔬菜种子截获各类有害生物48种496种次,其中真菌454种次,病毒2种次,细菌1种次,害虫2种次,杂草37种次,携带土壤1种次。【结论】入境台湾蔬菜种子携带有害生物种类繁多,但检疫性有害生物种类集中,应加强入境台湾蔬菜口岸检验检疫的对策措施,包括加强法规宣传、了解疫情动态、强化检疫工作等。