The relationship between conidial dose, moulting and insect developmental stage on the susceptibility of cotton aphid,Aphis gossypii, to conidia ofLecanicillium attenuatum, an entomopathogenic fungus (original) (raw)
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African Entomology, 2010
In an attempt to screen potential native entomopathogenic fungi for microbial control of cotton/melon aphid, we investigated the effect of temperature on the pathogenicity of some hyphomycete fungi. The virulence of four Beauveria and two Metarhizium isolates on adult Aphis gossypii was evaluated with a direct spraying bioassay at 20°C, 25°C and 30°C temperature regimes under laboratory conditions. The result of the bioassay showed that at 25°C and 30°C, all the isolates were virulent. Accordingly, cumulative target percentage mortality of Aphis gossypii at 25°C varied from 73.33-93.33 % mortality and LT50 ranged from 3.83 to 4.98 days while percentage cumulative target mortality and LT50 values at 30°C ranged from 82.22-100 % and 3.23-4.02 days, respectively. A statistically significant interaction between fungal isolates and temperature indicated that the pathogenic nature of an isolate was dependent on the temperature conditions of the bioassay. The results of the present study suggest that the use of native entomopathogenic fungi as an alternative method to chemical pesticides may hold promise for the management of Aphis gossypii in Ethiopia.
Aphidius colemani Viereck and A
Aphidius colemani Viereck and A. matricariae (Haliday) (Hymenoptera: Aphidiidae) have a high potential as effective biological control agents for the cotton aphid, Aphis gossypii Glover in greenhouse crops. In this study, the host stage preferences of A. colemani and A. matricariae were determined in a growth chamber at 25°C, 65 % relative humidity and during a photoperiod of 16L: 8D hours. In choice and no-choice experiments, individual females of A. colemani and A. matricariae were offered first, second, third and forth instar nymphs of A. gossypii, as well as adults. The results showed that there were significant differences between the mean percentages of parasitized hosts at different stages (P<0.05). Under no-choice conditions, the highest value was registered for parasitism of third instar nymphs of A. gossypii by A. colemani and of third and fourth instar nymphs by A. matricariae. In choice experiments, females of A. colemani and A. matricariae consistently preferred third and fourth instar nymphs of A. gossypii. Mean percentages for parasitism by A. colemani and A. matricariae on the third nymphal instar of A. gossypii were 23.6 ± 3.69 and 18.4 ± 2.42, respectively. The progeny body size of A. colemani and A. matricariae at emergence increased with host stage at the time of parasitization. The greenhouse release of parasitoids would be best timed to coincide with the period when third and fourth nymphal instars of cotton aphid are most abundant.
Egyptian Journal of Biological Pest Control, 2020
Background Effects of the entomopathogenic fungi Beauveria bassiana, Verticillium alfalfae, and Trichoderma viride; secondary metabolites of MS1 (B. bassiana) and MS2 (V. alfalfae); and Dimethoate active substances on the aphid species, Aphis gossypii Glover (Hemiptera: Aphididae), were tested. Main body of the abstract Fungus isolates were prepared as 107 conidia ml−1 of spore suspensions and applied on the 2nd instar nymphs of A. gossypii. After the applications, evaluations were made on the 1st, 3rd, 5th, and 7th days by counting the live individuals. Obtained data were 100 and 93% mortality rate at MS1 (B. bassiana) and MS2 (V. alfalfae), and secondary metabolites were recorded in the 3rd day count results. On the 5th day counts, the highest mortality rates after secondary metabolites were statistically at the same group with B. bassiana, T. viride, and dimethoate. On the 7th day, counting results of all experiment groups were analyzed statistically and were found effective. Sho...
The effects of two entomopathogenic fungal endophytes, Beauveria bassiana and Purpureocillium lilacinum (formerly Paecilomyces lilacinus), were assessed on the reproduction of cotton aphid, Aphis gossypii Glover (Homoptera:Aphididae), through in planta feeding trials. In replicate greenhouse and field trials, cotton plants (Gossypium hirsutum) were inoculated as seed treatments with two concentrations of B. bassiana or P. lilacinum conidia. Positive colonization of cotton by the endophytes was confirmed through potato dextrose agar (PDA) media plating and PCR analysis. Inoculation and colonization of cotton by either B. bassiana or P. lilacinum negatively affected aphid reproduction over periods of seven and 14 days in a series of greenhouse trials. Field trials were conducted in the summers of 2012 and 2013 in which cotton plants inoculated as seed treatments with B. bassiana and P. lilacinum were exposed to cotton aphids for 14 days. There was a significant overall effect of endophyte treatment on the number of cotton aphids per plant. Plants inoculated with B. bassiana had significantly lower numbers of aphids across both years. The number of aphids on plants inoculated with P. lilacinum exhibited a similar, but non-significant, reduction in numbers relative to control plants. We also tested the pathogenicity of both P. lilacinum and B. bassiana strains used in the experiments against cotton aphids in a survival experiment where 60% and 57% of treated aphids, respectively, died from infection over seven days versus 10% mortality among control insects. Our results demonstrate (i) the successful establishment of P. lilacinum and B. bassiana as endophytes in cotton via seed inoculation, (ii) subsequent negative effects of the presence of both target endophytes on cotton aphid reproduction using whole plant assays, and (iii) that the P. lilacinum strain used is both endophytic and pathogenic to cotton aphids. Our results illustrate the potential of using these endophytes for the biological control of aphids and other herbivores under greenhouse and field conditions.
European Journal of Entomology, 2007
The performance of the aphid-specific fungal pathogen Pandora neoaphidis was studied in relation to changes in herbivore resources for the pea aphid, Acyrthosiphon pisum, on different host plant species. Dose-response bioassays were conducted with A. pisum which had been reared on dwarf bean then inoculated with P. neoaphidis and returned to dwarf bean or inoculated and transferred to field bean, pea or lucerne. The smallest estimated median lethal concentration (LC50) was 7.7 conidia mm -2 (95% confidence interval 5.4-11.2) for aphids returned to dwarf bean, with LC50s of 13.0 (9.2-19.1) and 14.6 (10.2-21.5) conidia mm -2 for aphids transferred to field bean or pea, respectively. The LC50 when aphids were transferred to lucerne [2941.0 conidia mm -2 (237.3-2.1x10 9 )] was greater than for the other three plants. In a subsequent experiment, A. pisum were reared on pea as well as dwarf bean for four generations before bioassays. The LC50 was 7.3 conidia mm -2 (4.4-12.4) for aphids reared and incubated on dwarf bean, compared to 13.3 (8.0-23.9) and 15.3 (8.8-29.9) conidia mm -2 when aphids were transferred between dwarf bean and pea, and vice versa, respectively. The LC50 for aphids reared then incubated on pea plants was 27.9 (15.8-57.3) conidia mm -2 . Hence, the virulence of P. neoaphidis, measured by LC50, was greatest when A. pisum was reared and maintained on dwarf bean, the plant used for long-term routine culturing of the aphid in our facilities. In conclusion, virulence of P. neoaphidis was greater on plant species to which A. pisum had become adapted during long-term laboratory rearing. Plant resources may affect infection by P. neoaphidis and the fungal entomopathogen will have a greater impact on aphid herbivores which are not suffering physiological stress related to a change in host plant.
Applied Entomology and Zoology, 2014
Aphids (Homoptera: Aphididae) are sap-sucking insect pests that feed on several plants of agronomical importance. Entomopathogenic fungi are valuable tools for potential aphid control. As part of a selection process, laboratory bioassays were carried with five different concentrations of Aspergillus clavatus (Desmazières), Aspergillus flavus (Link) and Metarhizium anisopliae ((Metschnikoff) Sorokin) spores against the pea aphid, Acyrthosiphon pisum (Harris). Aspergillus isolates induced higher mortalities than M. anisopliae, which is a wellknown entomopathogen in the literature. Lethal concentrations (LC 50 and LC 90 ) were 1.23 9 10 3 and 1.34 9 10 7 spores/ml for A. flavus, 4.95 9 10 2 and 5.65 9 10 7 spores/ml for A. clavatus, and 3.67 9 10 3 and 9.71 9 10 7 spores/ml for M. anisopliae 5 days after treatment. Mycelia development and sporulation on adult cadavers were observed 48 h after incubation. The intrinsic growth rate of A. pisum decreased with increased spore concentration for all fungal strains, suggesting an increase in pathogen fitness related to a consumption of host resources. In conclusion, Aspergillus species could be useful in aphid control as pest control agents despite their saprophytic lifestyle. This is also to our knowledge the first report of A. clavatus and A. flavus strains pathogenic to aphids.
Influence of cotton plant on development of Aphis gossypii Glover (Homoptera: Aphididae
Experiments were carried out to determine population growth parameters of this pest and to compare its performance when feeding on detached leaves as opposed to the whole plant at constant temperature of 27 ± 1°C and 70 ± 5% of relative humidity. Results indicate that A. gossypii developed through four development stages with a mean development cycle of 4.38 ± 0.067 days. The doubling time of the aphid population was higher on whole plants (2.25 ± 0.02 days) than on detached leaves (1.91 ± 0.02 days). Similarly, the reproduction rate (Ro) of A. gossypii was lower on whole plants (16.023 ± 1.32) than on detached leaves (33.35 ± 1.68). Development, survivorship and reproduction of the aphid were negatively impacted by whole cotton plants, suggesting the possible induction of defence mechanisms.
Performance of cotton aphid Aphis gossypii (Hemiptera: Aphididae) lineages on cotton varieties
International Journal of Pest Management, 2006
The performance of three clonal lineages of Aphis gossypii Glover originating from central Greece was studied on six commercial cotton cultivars that differ with respect to leaf pubescence traits (Zeta-2, Zeta-5, Eva, Korina, Acala-SJ2 and Sindos-80). Two main laboratory experiments were conducted: (i) one clonal lineage was studied on all six varieties; and (ii) four varieties were assayed with two other lineages. Aphid development, fecundity, longevity and mortality were recorded and life-table characteristics estimated for all varieties. The results showed that leaf trichome density was significantly correlated with aphid performance (i.e. positive correlation with intrinsic rate of increase and fecundity, and negative correlation with developmental time) in both experiments. Leaf hairiness was at least partly responsible for the poorer performance in cotton aphid lineages. We hypothesise that other factors such as allelochemicals (e.g., gossypol, tannins), which are known to affect hemipteran insects, also might be involved.