Correlation-Based Network Analysis of the Influence of Bemisia tabaci Feeding on Photosynthesis and Foliar Sugar and Starch Composition in Soybean

Bemisia tabaci (MEAM1) represents a species of economic importance in soybean. One of the obstacles to the management of B. tabaci is the quantification of damage by the pest because damage is indirectly inferred through losses in productivity. The objective of this study was to characterize the influence of B. tabaci feeding on soybean by assessing effects on photosynthetic parameters and the sugar and starch content of soybean leaves. The goal was to identify the optimal parameter to directly quantify pest damage on crop yield. Correlation networks were created among data on sugar content (fructose, glucose, and sucrose), starch and photosynthetic parameters (initial fluorescence, performance index on absorption basis, and turn-over number), and the number of nymphs at each of three infestations level (low, medium, and high) during both the vegetative and reproductive stage of the crop. In general, nymphs were more abundant during the vegetative stage. Starch content was strongly correlated with nymph density. A strong positive correlation was observed between fructose and nymph density during the vegetative stage. Among the photosynthetic parameters, the turn-over number N was positively correlated with nymph density at a low-infestation level and negatively correlated with nymphs when they occurred at a high-infestation level. B. tabaci feeding affected the plant’s physiology and its interaction is reflected in part by the relationships among photosynthetic parameters as well as the levels of sugars and starch. This understanding might be useful in developing better monitoring tools for pest management.

Toward understanding the impact of nuisance algae bloom on the reduction of rice seedling emergence and establishment

California rice (Oryza sativa L.) production has been recently challenged by the early season bloom of nuisance algae. The algal community in rice is a complex of green algae (Nostoc spongiforme Agardh ex Bornet) and cyanobacteria species that could develop a thick algal mat on the surface of the water and interfere with the emergence and establishment of rice seedlings. The objective of this research was to determine the impact of algae infestation level on rice seedling emergence. A mesocosm study was conducted in 57 L tubs. Three levels of algae infestation (low, medium, and high) were produced by adding fertilizer N:P amount into the tubs including 0:0, 75:35, and 150:70 kg-1ha. Sixty rice seeds (M-206) were soaked for 24 hours and spread into tubs filled with water. Photosynthetic Active Radiation (PAR), Chlorophyll a concentration as the quantitative measure of algae, number of emerged rice seedlings, and their dry biomass were studied during the experiment. Results showed that algae infestation can directly change the amount of light received into the water. Minimum, maximum and mean percentage of PAR inside the water declined by the increase of algae infestation level. As a consequence, rice seedling emergence dropped under the high algae pressure. At very high algae infestation (i.e. chlorophyll a concentration of above 500 µg ml-1), rice seedling emergence reduced up to 90%. Furthermore, rice seedling emergence was delayed under algae infestation. When algae infestation was low, time to 50% of rice seedling emergence (t50) ranged between five and ten days, while at high algae infestation t50 ranged between twelve and twenty days. Moreover, individual rice seedling biomass reduced from one gram to 0.01 gram by the increase of algae infestation. The results from this study indicate that uncontrolled algae at the beginning of the rice-growing season could reduce rice seedling emergence, establishment, and rice stand. Given that algae infestation in field has a patchy pattern, loss of rice stand in these patches could provide empty niches for other weeds to grow.

Field infestation level of Zaprionus indianus Gupta and Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) in Ficus carica L. (Rosales: Moraceae) and Rubus idaeus L. (Rosales: Rosaceae) in the Northeast of Buenos Aires province

Two exotic fruit flies species, Zaprionus indianus Gupta and Drosophila suzukii (Matsumura), were detected in Argentina in recent years. In this note, the southernmost detection of Z. indianus in Argentina and an estimation of the field infestation level caused by both drosophilid species on figs (Ficus carica L.) and raspberries (Rubus idaeus L.) are reported.

The Erythrina Gall Wasp Quadrastichus erythrinae (Insecta: Hymenoptera: Eulophidae): Invasion History, Ecology, Infestation and Management

The Erythrina gall wasp Quadrastichus erythrinae Kim (Hymenoptera: Eulophidae) is an invasive insect that induces galls on coral trees (species of Erythrina, Fabaceae) in urban and suburban landscapes. Weakening and death of the tree were both observed after the infestation by this insect, wherein feeding and consequent draining of nutrients by a large population of Q. erythrinae could be playing a key role. In this article, we consolidate and summarize the information on the distribution, invasion route, ecology, infestation level, and management of Q. erythrinae populations in the last two decades and analyze the challenges in their management.

Tick (Acari: Ixodidae) infestation of cuscuses from Maluku Province, Indonesia

Background and Aim: Cuscuses are one of the endemic Indonesian marsupials, which needs to be protected and revived in terms of the numbers and range of species. Ectoparasites of ticks (Ixodidae) are one potential obstacle to cuscus conservation. Tick infestation can cause blood loss in the host, even being a predisposing factor for infection with pathogenic organisms. This study aimed to determine the prevalence, infestation intensity, and species of ticks present on cuscuses in Maluku Province, Indonesia. Materials and Methods: Ticks were collected from cuscuses origin of the four regions in Maluku Province, namely the island of Ambon, Seram Island, Romang Island, and Wetar Island . Cuscuses were captured at night, with ticks being collected from them from the head to the tip of the tail. The tick samples obtained from the cuscuses were preserved, identified, and counted. Cuscuses were released back into their habitat after collecting the ticks. The obtained ticks were observed using an Olympus BX51 microscope with an Olympus DP12 digital camera and prepared for examination under a scanning electron microscope (SEM). Infestation rate, infestation intensity, and morphology of the species were described. Results: The cuscuses were found to be infested with Ixodes cordifer ticks. Cuscuses in Maluku Province had a low tick infestation rate. The range of infestation prevalence of island origin cuscuses in Maluku was between 14.28% and 16.67%. Simultaneously, I. cordifer infestation level was mildly infested based on the intensity of thick infestation ranged from 1 to 1.2 ticks per cuscus. From observation of the tick surface structure under SEM, sexual dimorphism and various specific characteristics of the ticks were identified. Conclusion: The low infestation rate of I. cordifer ticks in cuscus was influenced by the up and down movement of the conscious activity in the tree, which allowed minimal contact with the ticks. The infestation prevalence rates on each island studied were similar. Such similarities of infestation are related to the similarity of cuscus species among Ambon, Lakor, Seram, and Romang islands, which are all included in the Phalangeridae family, and their similar habitats, behaviors, climatic conditions, and geographical areas.

Distribution and Impact of Parthenium (Parthenium hysterophorus L.) on Weed Species Diversity in Maize Fields in Western Gojjam Zone, Amhara National Regional State, Ethiopia

An investigative weed flora survey was conducted in parthenium-infested maize fields in West Gojjam Zone in 2019/2020. The objective was to investigate the distribution and impact of parthenium on species diversity. A survey was conducted on 90 fields using 2 m × 2 m (4 m2) quadrats (totally 270). A total of 110 weed species belonging to 27 families were identified out of these families. Asteraceae with 26 species (23.36%) and Poaceae with 18 species (16.36%) were abundant. The highest importance value (IV) was recorded by Ageratum conyzoides, Amaranthus hybridus, and Bidens pilosa, with 28.05, 19.18, and 13.16%, respectively, in no parthenium infestation level. The highest IV of 27.08, 17.71, and 16.44%, respectively, was shown by Ageratum conyzoides, Bidens pilosa, and Galinsoga parviflora with 27.08, 17.71, and 16.44%, respectively, in very low parthenium infestation level. Ageratum conyzoides (29.38%), Bidens pilosa (24.10%), and Parthenium hysterophorus (22.68%) had the highest IV in low parthenium infestation level. Parthenium hysterophorus (91.32%), Ageratum conyzoides (17.19%), and Echinochloa colona (16.34%) had high IV in moderate parthenium infestation level. It is concluded that Ageratum conyzoides, Bidens pilosa, Echinochloa colona, and Galinsoga parviflora were competitive over parthenium based on importance value, and this indicates to suggest parthenium as a biological management option.