Potentials of compost, compost tea and aqueous neem leaves extract in reducing some diseased plants and boosting onion (Allium cepa L.) production in the field at Gapring-Lara in t he Department of Mayo Kani (Cameroon)

With a view to promoting the onion sector, we studied the behavior of onion following the application in fields of Cow Dung compost, compost tea and the aqueous extract of neem leaves during the 2018/2019 and 2019/2020 growing seasons. The device used was a complete randomized block comprising 10 treatments including compost (Cp), compost tea (CpT), Neem extract (Nex), compost + compost tea (Cp+CpT),compost+Neem extract (Cp+Nex), compost tea+Neem extract (CpT+Nex), compost+Compost Tea+NeemExtract (Cp+CpT+Nex), Control (Ctrl), Chemical Pesticide (ChP) and Chemical Fertilizer (ChF) with 3 repetitions each. The work focused on agronomic and phytopathological parameters. The results reveal that Cp+CpT+Nex treatment had a highly significant influence on the germination rate (92.33%) than Ctrl treatment (44%). He was significantly increased the number of leaves, size and yield compared to other treatments with 22.16 leaves, 52 cm and 114.74 t/ha (2018/2019) and 20.83 leaves and 53.84 cm; but yield was higher by ChF with 47.49 t/ha (2019/2020). Nex, Cp+Nex and CpT+Nex treatments reduced attack of Delia antiqua compared to control. And significant reduction in number of plants attacked by onion mildew was observed in Cp+CpT+Nex treatment. In view of the results obtained, organics fertilizers can be used in onion production.

Bacterial Inhibition on Beauveria bassiana Contributes to Microbiota Stability in Delia antiqua

Given the multiple roles of associated microbiota in improving animal host fitness in a microbial environment, increasing numbers of researchers have focused on how the associated microbiota keeps stable under complex environmental factors, especially some biological ones. Recent studies show that associated microbiota interacts with pathogenic microbes. However, whether and how the interaction would influence microbiota stability is limitedly investigated. Based on the interaction among Delia antiqua, its associated microbiota, and one pathogen Beauveria bassiana, the associated microbiota's response to the pathogen was determined in this study. Besides, the underlying mechanism for the response was also preliminarily investigated. Results showed that B. bassiana neither infect D. antiqua larvae nor did it colonize inside the associated microbiota, and both the bacterial and fungal microbiota kept stable during the interaction. Further experiments showed that bacterial microbiota almost completely inhibited conidial germination and mycelial growth of B. bassiana during its invasion, while fungal microbiota did not inhibit conidial germination and mycelial growth of B. bassiana. According to the above results, individual dominant bacterial species were isolated, and their inhibition on conidial germination and mycelial growth of B. bassiana was reconfirmed. Thus, these results indicated that bacterial instead of fungal microbiota blocked B. bassiana conidia and stabilized the associated microbiota of D. antiqua larvae during B. bassiana invasion. The findings deepened the understanding of the role of associated microbiota–pathogen microbe interaction in maintaining microbiota stability. They may also contribute to the development of novel biological control agents and pest management strategies.

Symbiotic Bacterium-Derived Organic Acids Protect Delia antiqua Larvae from Entomopathogenic Fungal Infection

ABSTRACT Colonization resistance, i.e., the protective effects of associated microbiota for the animal host against pathogen infection, has been studied widely over the last 100 years. However, few molecules mediating colonization resistance have been identified. In the symbiosis formed by Delia antiqua and its associated microbes, six bacteria protect larvae from infection with the entomopathogen Beauveria bassiana, providing an ideal model to investigate the chemical mechanism for colonization resistance. Subsequently using this symbiotic system, we first compared effects of the six bacterial species, and one control bacterium (Klebsiella oxytoca) that showed no antifungal effects, on B. bassiana and its infection of D. antiqua. Second, metabolomic profiles of the six bacteria and K. oxytoca were compared to identify candidate metabolites that may prevent infection. Third, the concentrations of candidate metabolites in situ from axenic and nonaxenic larvae were determined. Finally, effects of artificial metabolite cocktails on B. bassiana and its infection of D. antiqua larvae were determined. Results showed that compared to K. oxytoca, the six bacteria produced a metabolite cocktail showing inhibitory effects on conidial germination, mycelial growth of B. bassiana, and fungal infection. Our work revealed novel molecules that mediate colonization resistance, which could help in developing chemical mechanisms of colonization resistance. Moreover, this work may aid in discovery and expansion of new bioactive antibiotics, promoting development of prophylactic and therapeutic approaches for treating infectious diseases. IMPORTANCE The protection of associated microbiota for their animal hosts against pathogen infection has been studied widely over the last 100 years. However, how those microbes protect the animal host remains unclear. In former studies, body surface microbes of one insect, Delia antiqua, protected the insect larvae from infection with the entomopathogen Beauveria bassiana. By comparing the metabolites produced by microbes that protect the insect and microbes that cannot protect the insect, the question of how the microbes protect the insect is answered. It turns out that body surface bacteria produce a metabolite cocktail that inhibits colonization of B. bassiana and consequently protects the insect. This work reveals novel molecules with antifungal activity, which may aid in discovery and expansion of new prophylactic and therapeutic natural chemicals for treating infectious diseases.

Oviposition, Feeding Preferences and Distribution of Delia Species (Diptera: Anthomyiidae) in Eastern Canadian Onions

Delia antiqua, Delia platura and Delia florilega are three root maggot species commonly considered pests in Eastern Canadian onions. The onion maggot, D. antiqua, is considered the primary root maggot pest in onion but it remains unclear whether the other two species are also causing damage. In order to develop updated management strategies for root maggot, we tested adult oviposition and feeding preference by Delia larvae on four growth stages of onion using bioassays and we determined the Delia species composition across the four major onion growing regions in eastern Canada. Delia species oviposit readily on onion at the 5–7 true leaf growth stage but damage on onions is not statistically different between Delia species in our zero-inflated models. The four eastern Canadian onion growing regions have different proportions of Delia species. Southern Ontario and Quebec were the only two regions where Delia antiqua was collected. The highest average numbers of Delia spp. were caught in Quebec and Nova Scotia. Our study shows that timing is important in implementation of management strategies for root maggot in Eastern Canadian onions.

Oviposition in the onion fly Delia antiqua (Diptera: Anthomyiidae) is socially facilitated by visual cues

Ovipositional decisions in herbivorous insects may be affected by social information from conspecifics. Social facilitation of oviposition has been suggested for the onion fly Delia antiqua. In the current study, we found that D. antiqua oviposition was unequal between paired oviposition stations of equal quality and that more eggs were laid on an oviposition station baited with decoy flies than on the control. The increased oviposition toward the decoys continued over time >8 h. When decoys were placed upside down, the number of eggs laid did not differ between the decoy and control sides of oviposition stations, suggesting that social facilitation of oviposition is mediated by visual cues. Based on these findings, mechanisms of social facilitation of oviposition in D. antiqua were discussed.

Biological traits and susceptibility of Delia antiqua (Meigen, 1826) (Diptera: Anthomyiidae) in onion

The pre-oviposition period of mated and unmated female reared on Bangladeshi and Indian onion was 4.5 ± 0.5, 4.37 ± 0.6 days and 4.11 ± 0.09, 4.45 ± 0.32 days, respectively. The oviposition period of mated and unmated female was 5.6 ± 0.6, 6.03 ± 0.6 days and 6.48 ± 0.39, 6.5 ± 0.34 days reared on Bangladeshi and Indian onion, respectively. The life cycle of Delia antiqua consisted of four definite stages: egg, larva, pupa and adult. The incubation period was1.38 ± 0.11 and 1.25 ± 0.05 days; larval period was 5.7 ± 0.7 and 5.4 ± 0.05 days; pupal period was 6.8 ± 0.2 and 6.08 ± 0.2 days, respectively. There were three larval instars in D. antiqua. To complete the total life cycle it required shorter period in Indian than in Bangladeshi onion. The total life cycle of female was 16.73 ± 0.89 and 15.29 ± 0.45 days, respectively on Bangladeshi and Indian onion. The difference between the life cycle of female was significant (p < 0.05) in Bangladeshi and Indian onion. Fecundity was higher in Indian than in Bangladeshi onion. The fecundity of female D. antiqua reared in Bangladeshi and Indian onion was 75.2 ± 4.09 and 89.2 ± 2.39, respectively and it was significantly (p < 0.05) varied. Female lived longer than male D. antiqua. It was more susceptible in Indian than Bangladeshi onion irrespective of the duration of life cycle and fecundity. Bangladesh J. Zool. 47(2): 325-332, 2019