Progress 01/03/15 to 12/03/15
Outputs
Progress Report Objectives (from AD-416): Objective 1: Determine the effect of temperature and reproductive state on susceptibility of tarnished plant bugs to Beauveria (B.) bassiana (ARSEF 8889). Objective 2: Determine the effect of exposure to insect growth regulators (IGRs) and B. bassiana (ARSEF 8889) on immature tarnished plant bug survival. Objective 3: Determine the effect of host plant and application timing (season) on susceptibility of tarnished plant bugs treated with ARSEF 8889 and IGRs (in situ). Approach (from AD-416): The effect of temperature and reproductive state on the susceptibility of tarnished plant bugs to Beauveria (B.) bassiana (ARSEF 8889) will be determined in replicated laboratory tests. The two reproductive states tested will be normal reproductive adults and nymphs and diapausing adults and nymphs that produce diapausing adults. Temperatures tested will range from 10�C to 30�C. Insect growth regulators (IGRs) will be tested with nymphs in replicated laboratory tests to determine which IGRs are effective and the rate at which to use them. The most effective IGR(s) will be tested in laboratory tests in combination with ARSEF 8889 to determine the most effective combination treatment. Results from the laboratory tests will be tested in the field in replicated tests in cotton (for in-season plant bug control) and in the fall and winter on wild host plants (for control of the diapausing overwintering generation). The effect of IGRs and ARSEF 8889 treatment on beneficial arthropod populations will be evaluated in the field tests and with additional laboratory tests. Serves as the final report for project 6066-22000-083-00D. This project was replaced by project 6066-22000-088-00D. Tarnished plant bugs were collected from wild host plants at different locations in Mississippi, Louisiana, and Arkansas during 2015. Adults and nymphs from each location were kept individually for 15 days on solid diet and checked daily for parasitism or microbial infection. Low levels of parasitism (<1%) by Phasia spp. were found in samples collected from Goodman, Mississippi. A range in parasitism of TPB from 0 to 55% was associated with two unidentified braconid species in samples from Mississippi, Louisiana, and Arkansas. The highest parasitism observed was in samples from Hamburg, AR (55%) and Lake Providence, LA (27%). Larvae of Phasia spp emerged from parasitized TPB adults. The two braconid species emerged from adult TPB (>99%) and fourth-fifth instar nymphs (<1%) . Presence of parasitism of TPB was first observed in early April with continuing observations through early June. Parasitism of TPB was not observed during the summer, but parasitism by braconid parasitoids (<1%) was again observed in late October. Natural incidence of several microbial agents was also found. Measured infection rates in Mississippi, Arkansas and Louisiana ranged from 0 to 15%, 0 to 3%, and 0 to 18%, respectively. Results of these studies are a component of life table studies examining ecological targets for microbial control of TPB populations. Field experiments were carried out to evaluate the effects of temperature and sunlight on viability of the Mississippi Delta native NI8 strain. Detailed observations were made on the effects of solar radiation by releasing 30 two-d old TPB adults in cages with sprayed branches of cotton plants removed from field plots at time intervals of 0, 2, 4, 6, 8, 10, 24, 26, 28, 30, 32, 48, 50, 52, and 54 h after NI8 was applied. The top of a single cotton plant from each field plot was removed at approximately 10 nodes below the crown of the plant at each evaluation time. Adult TPBs from the sprayed branches were individually placed into diet cups. Insects were held in an environmental room and examined daily for 10 d for sporulation. Sporulation of TPB exposed to sprayed cotton branches for 0 hours (69%) was significantly different among treatments. Sporulation decreased drastically by 1.4-fold at 4-h (48%) and to 9.2- fold at 10-h (7.5%). However, sporulation then increased 3.3-fold the next day (25%) (24 h evaluation), decreasing again 2.5-fold over the next 10 hours (10%). Less than 10% sporulation was found two-d after application of NI8. Overall, these results indicate that B. bassiana application could decrease survival of TPB exposed to NI8 through contact activity. However, inability of the fungus to survive solar radiation is an important obstacle for efficacy and use of this entomopathogenic fungus for the control of TPB. The >69% sporulation observed in TPB adults from contact at 0-h suggested that this fungi may be an attractive alternative to conventional TPB control options. Preliminary field experiments were carried out to determine the action of NI8 as a fungal endophyte. Seeds of corn, soybean and cotton (1 Kg each) were surface sterilized in 1.5% sodium hypochlorite for 10 min and rinsed twice in sterile distilled water. Haft of the seeds (500 g each) were then immersed in a 6X1012 mL-1 suspension of Beauveria bassiana for 2 hours. Remaining seeds were immerged in 0.04% Tween-80 solution for 2 hours. Group of seeds of corn, soybean, and cotton (both fungus treated and untreated) were planted in the field in plots of 4 rows wide and 25 feet long. Three plants per row per treatment were collected each week for 4 weeks beginning 14 days after planting. Collected plants were surface sterilized and rinsed as mentioned above. Small parts of each plant were cut (node, internode, vegetative branch, petiole, blade, and stem) and inoculated into plates of Sabouraud Dextrose Agar Primix (SDAY) and incubated for 3 days. Sporulation was found in each part of the cotton, corn, and soybean plants collected from the field at the third week after planted. However, only mycelium was obtained after the second to fourth week of collection. Cotton leaves with presence of external mycelium were exposed to TPB adults. Insects walked on the mass of hyphae with no mortality effects. Plots of cotton were planted adjacent to corn and mustard to study possible control of tarnished plant bugs by spraying corn with the NI8 strain prior to movement of bugs into cotton. Differences in tarnished plant bug numbers were noted on a few sample dates, but it appeared that larger plots are needed to measure plant bug suppression by the entomopathogenic fungus. Both adult and nymphs of TPB from the samples collected across the delta were subjected to stable carbon isotope (SCI) analysis. This analytical technique has the ability to differentiate between insects that developed on C4 hosts (corn and pigweed) and C4 hosts (most broad leaved plants, including soybean and cotton). Approximately 20 adults and up to 20 nymphs were removed from each of the collections. Samples are currently being processed and data from the first year of collections are being evaluated. Tarnished plant bug virus 2 (Llv-2) is a small RNA virus lethal to Lygus species. The positive sense single stranded genome of Llv-2 is 10,035 nucleotides and contains three open reading frames that codes for three different polypeptides. Virulence and the possibility of endophytic transmission of Llv-2 was tested using homogenates and sucrose gradient purified virus, respectively. Feeding diet mixed with homogenates of infected insects caused 100% mortality of test insects in 3 days. However, endophytic transmission was not detected in corn and cotton plants surface inoculated at two-leaf stage with purified virus particles.
Impacts
(N/A)
Publications
- Portilla, M., Jones, W.A., Perera, O.P., Seiter, N., Greene, J., Luttrell, R.G. 2016. Estimation of Median Lethal Concentration of Three Isolates of Beauveria bassiana for Control of Megacopta cribraria (Heteroptera:Plataspidae) Bioassayed on Solid Lugys Spp. Diet� . Insects. 7(3):31;doi:10.3390/insects7030031.
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Progress 10/01/14 to 09/30/15
Outputs
Progress Report Objectives (from AD-416): Objective 1: Determine the effect of temperature and reproductive state on susceptibility of tarnished plant bugs to Beauveria (B.) bassiana (ARSEF 8889). Objective 2: Determine the effect of exposure to insect growth regulators (IGRs) and B. bassiana (ARSEF 8889) on immature tarnished plant bug survival. Objective 3: Determine the effect of host plant and application timing (season) on susceptibility of tarnished plant bugs treated with ARSEF 8889 and IGRs (in situ). Approach (from AD-416): The effect of temperature and reproductive state on the susceptibility of tarnished plant bugs to Beauveria (B.) bassiana (ARSEF 8889) will be determined in replicated laboratory tests. The two reproductive states tested will be normal reproductive adults and nymphs and diapausing adults and nymphs that produce diapausing adults. Temperatures tested will range from 10�C to 30�C. Insect growth regulators (IGRs) will be tested with nymphs in replicated laboratory tests to determine which IGRs are effective and the rate at which to use them. The most effective IGR(s) will be tested in laboratory tests in combination with ARSEF 8889 to determine the most effective combination treatment. Results from the laboratory tests will be tested in the field in replicated tests in cotton (for in-season plant bug control) and in the fall and winter on wild host plants (for control of the diapausing overwintering generation). The effect of IGRs and ARSEF 8889 treatment on beneficial arthropod populations will be evaluated in the field tests and with additional laboratory tests. This is a replacement/bridging projet for 6066-22000-064-00D. For further information refer to the annual report for 6066-22000-064-00D. The entomopathogenic fungus Beauveria (B.) bassiana strain NI8 was evaluated for compatibility with two insect growth regulators under field condition in summer 2014. Sixteen plots eight rows wide and 15.24 m long (124.08 m2) were planted with Bollgard II (BGII) cotton expressing Cry1Ac and Cry2Ab toxin of Bacillus thuringiensis. Treatments (untreated control, NI8, NI8+novaluron, NI8+pyriproxyfen) were replicated four times and were applied with a multi-boom sprayer immediately following an initial plot insect assessment for tarnished plant bugs (TPB). Concentration of B. bassiana was 1.5x1013 (spores/ha). All sprays included 0.40 mL of Tween- 80 per 1 L of spray. No significant differences were found in lint yield between B.bassianna + pyriproxyfen, B. bassina, and the untreated control. Plots treated with the combination treatment B. bassiana+novaluron resulted in significantly higher yields than the other treatments. Diet overlay assays were conducted to evaluate the effect of six insecticides alone and in combination for mortality of TPB by contact. Each treatment was overlayed on solid artificial diet for Lygus. Adult mixed-sex, 0-D old, and fifth instar nymphs were used. Insects were examined daily for five day for mortality. When exposed to artificial diet overlayed with the treatments clothianidin, flonicamid, and clothianidin+pyriproxyfen in the laboratory, TPB nymphs experienced 100% mortality by contact 1 day after exposure. TPB nymphs exposed to acephate and acephate+lambda- cyhalothrin also suffered high mortality after 1 day (85%), with the remainder perishing 2 days after exposure. Pyriproxyfen and clothianidin slowly increased mortality by day 3, however 20% of the population survived the application. No treatment had lower mortality than the untreated control. Adult TPB experienced 100% mortality after 3 hours when exposed to diet overlayed with flonicamid or lambda- cyhalothrin+acephate. TPB adults exposed to clothianidin experienced >50% mortality at 0 day following treatment and nearly 100% mortality was observed for this treatment after 4 days of exposure. There was <5% mortality of adults exposed to diet overlayed with pyriproxyfen, water, or the untreated control. In the diet overlayed with novaluron, TPB adult mortality never exceeded 30%. Laboratory assays also were conducted to evaluate the effect of six insecticides alone and in combination for mortality of TPB by direct spray. All treatments were applied using a specially designed spray tower. Insects were held in an environmental room at 27�C, 65% RH, and 12L: 12D photoperiod and examined daily for five day for mortality. Mortality of TPB nymphs at 1 day was 100% after sprayed with all treatments except for lambda-cyhalothrin, untreated and water control. No differences in mortality were observed between lambda- cyhalothrin, untreated and the water control at day 4 and 5 post- application. Significant differences among treatments were observed for each time of evaluation. Adult TPB experienced 100% mortality after 3 hours after spray when exposed to diet with clothianidin or lambda- cyhalothrin+acephate. TPB adults exposed to flonicamid experienced >10% mortality at 0 day following treatment, increasing just to 20% at day 2 after spray. Nearly 90% mortality was observed for this treatment after 5 days of exposure. No significant differences were found among pyriproxyfen, water, or the untreated control at any evaluation time.
Impacts
(N/A)
Publications
- Shelby, K., Perera, O.P., Snodgrass, G.L. 2015. Expression profiles of Astakine-like transcripts in the tarnished plant bug, Lygus lineolaris, exposed to fungal spores of Beauveria bassiana. Insect Molecular Biology. 24(4):480-490. DOI:10.1111/imb.12175.
- Portilla, M., Snodgrass, G.L., Luttrell, R.G. 2014. Artificial diets for life tables bioassays of TPB in Mississippi. Midsouth Entomologist. 7:128- 135.
- Portilla, M., Snodgrass, G.L., Luttrell, R.G. 2014. Mississippi Delta native strain of Beauveria bassiana for control of TPB. Midsouth Entomologist. 7:82-88.
- Portilla, M. 2014. Biological control as an alternative measure for TPB in Mississippi. Midsouth Entomologist. 7:38-46.
- Portilla, M., Snodgrass, G.L., Luttrell, R.G. 2014. A novel bioassay to evaluate the potential of Beauveria bassiana strain NI8 and the insect growth regulator novaluron against Lygus lineolaris on a non-autoclaved solid artificial diet. Journal of Insect Science. 14:1-13. Available online:
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