Efficacy of Entomopathogenic Trichoderma Isolates against Sugarcane Woolly Aphid, Ceratovacuna lanigera Zehntner (Hemiptera: Aphididae)

Ceratovacuna lanigera Zehntner (Hemiptera: Aphididae) is a destructive insect pest of sugarcane that is responsible for reducing the quality, yield, and sugar content. Ecofriendly methods of pest control, such as the use of biological control, is encouraged since it does not exhibit the harmful effects that are usually seen when using chemical-based pesticides. Here, we evaluated the efficacy of several entomopathogenic fungi isolates against C. lanigera under laboratory conditions. A total of seven isolates were obtained from agricultural soils that were collected from various locations from Sabah, Malaysia, using the insect bait method. Among the seven, four isolates (TMS114, TMS623, TMS628, and TMS707) were positively identified as T. harzianum (Hypocreales: Hypocreaceae), two isolates (TMS45, TMS321) as T. asperellum (Hypocreales: Hypocreaceae), and one isolate (TMS633) as T. hamatum (Hypocreales: Hypocreaceae) based on a combination of morphological characteristics and molecular data using ITS 1-5.8 S-ITS 2 regions of the rDNA. Four different concentrations (1 × 105, 1 × 106, 1 × 107, and 1 × 108 mL−1) of conidia suspensions of the isolates were applied separately on nymphs and adults of C. lanigera. The results showed that mortality in both nymphs and adults was dependent on the conidia concentration and exposure time. Among the four concentrations, the highest mortality of C. lanigera was found to range from 59.99 to 75.70% for nymphs after 72 h and from 57.45 to 72.31% for adults after 6 days of treatments at the concentration of 1 × 108 conidia mL−1. Trichodermaharzianum (TMS623) showed significantly highest mortality of 75.70% for nymphs and 72.31% for adults among the seven isolates. . However, the nymph and adult mortality rates for the isolates were 70.00% & 68.00% for TMS114, 66.42% & 63.10% for TMS628, 67.85% & 65.24% for TMS707, 61.42% & 58.80% for TMS45, 59.99% & 57.45% for TMS321 and 63.56% & 60.91% for TMS633, respectively. For nymph mortality, T. harzianum (TMS623) showed a LC50 (lethal concentration) value of 6.30 × 105 conidia mL−1 and LC90 value of 3.01 × 109 conidia mL−1, respectively, and for adult mortality, the values were found of 6.16 × 105 conidia mL−1 for LC50 and 2.23 × 1010 conidia mL−1 for LC90, respectively. The lethal time (LT) values for nymph and adult mortality were found of 42.65 h and 3.89 days for LT50 and 93.32 h and 8.70 days for LT90 by T. harzianum (TMS623). Therefore, T. harzianum (TMS623) showed more pathogenic potential against C. lanigera and can be further applied to determine its efficacy under field conditions. To our best knowledge, this is the first report of T.harzianum,T.hamatum, and T.asperellum species that are used as entomopathogenic fungi against sugarcane woolly aphid, C. lanigera.

The entomopathogenic fungal endophytes Purpureocillium lilacinum (formerly Paecilomyces lilacinus) and Beauveria bassiana negatively affect cotton aphid reproduction under both greenhouse and field conditions

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.