Location: Southern Insect Management ResearchTitle: Infectivity of Entomopathogenic fungal isolates against tarnished plant bug
|MANIANIA, NGUYA - Crop Defenders Ltd|
|AMNULLA, FAYAZ - Crop Defenders Ltd|
|MFUTI, DAVID - International Centre Of Insect Physiology And Ecology|
|DARIE, ANDREI - Crop Defenders Ltd|
|DHIMAN, GEETIKA - Crop Defenders Ltd|
|RAO, ISHTIAQ - Crop Defenders Ltd|
Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2022
Publication Date: 7/5/2022
Citation: Maniania, N.K., Portilla, M., Amnulla, F.M., Mfuti, D.K., Darie, A., Dhiman, G., Rao, I.M. 2022. Infectivity of Entomopathogenic fungal isolates against tarnished plant bug. Journal of Insect Science. 22:1-7. https://doi.org/10.1093/jisesa/ieac040.
Interpretive Summary: The tarnished plant bug (TPB), is the most common phytophagous species of the genus Lygus in North America. It causes damages to vegetables, fruits, greenhouse crops, canola, and legume crops . Since crops are often infested with several different stages of the pest, understanding which stage is most susceptible to infection is important for the development of management tactics. The present study investigates, the pathogenicity of entomopathogenic fungal isolates against TPB to select the most virulent isolate(s) and to compare the susceptibility of different developmental stages to the selected fungal isolate. In addition, the performance of the selected candidate in a greenhouse trial was evaluated.
Technical Abstract: Twelve isolates of entomopathogenic fungi belonging to Metarhizium robertsii, M. pinghaense, M. brunneum, Beauveria bassiana and Isaria fumosorosea were screened against adult tarnished plant bug (TPB). All isolates were pathogenic, causing mortality from 28.8 ± 3.4 to 96.3 ± 2.7%. The lethal time to 50% mortality (LT50) values ranged from 2.7 to 6.0-d while lethal time 90% mortality (LT90) values varied between 6.6-d and 15.0-d. M. robertsii isolate CPD6 was among the isolates that caused high mortality within shorter times and was selected for study on developmental stages and greenhouse trial. The 3rd, 4th and 5th instar nymphs, and adults were inoculated with 106, 107 and 108 conidia mL-1 of M. robertsii CPD6. All the stages were susceptible to fungal infection. However, 3rd and 4th instars were the most susceptible with no significant differences in mortality across the three concentrations (F = 1.00; df = 2, 11; P = 0.41). On the other hand, mortality was dose-dependent with 5th-instar nymph (F = 4.60; df = 2, 11; P < 0.05) and adult stages (F = 37.6; df = 2, 11; P < 0.001). LT50 and LT90 values were also dose-dependent, with higher concentration having shorter lethal time values as compared to the lower concentrations. In the greenhouse, pepper plants were sprayed with CPD6 and chemical insecticide Flonicamid (as industrial standard), before releasing adult TPB. Mortality of 37.3, 75.5 and 76.3% was recorded in the control, CPD6 and Flonicamid, respectively. The present study has identified M. robertsii CPD6 as potential mycoinsecticide candidate for the control of L. lineolaris. It has also demonstrated that younger stages are more susceptible to fungal infection than older stages, an important factor that should be considered when applying mycoinsecticide in the field.