START: 01 JUN 2001 TERM: 31 MAY 2004 FY: 2004 GRANT YR: 2001
GRANT AMT: $156,709
INVESTIGATOR: Losey, J.
PERFORMING INSTITUTION:
ENTOMOLOGY
CORNELL UNIVERSITY
ITHACA, NEW YORK 14853
INOCULATIVE RELEASES OF TRICHOGRAMMA OSTRINAE FOR CONTROL OF EUROPEAN CORN BORER IN FIELD CORN
NON-TECHNICAL SUMMARY: European corn borer (ECB), Ostrinia nubilalis, is the most damaging pest of corn in the U.S. and Canada. One alternative tactic for managing ECB in field corn is biological control with inoculative releases of the egg parasitoid Trichogramma ostriniae, a species we have been working with for several years in fresh market sweet corn. Research since 1996 has provided impressive evidence that inoculative releases of T. ostriniae can successfully reduce ECB population levels and concomitant damage to sweet corn. In 2000, inoculative releases of T. ostriniae were made in 9 fields of sweet corn in New York. Approximately 47% of the total ECB eggs deposited over the season were parasitized. Furthermore, ECB damage to ears was reduced 50% compared with non-release fields. We are proposing to evaluate early-season inoculative releases of T. ostriniae for suppression of ECB in field corn in New York, Pennsylvania, Delaware, and Virginia. We will also investigate the overwintering of T. ostriniae in each state and assess potential non-target effects of the parasitoid by evaluating parasitism of other lepidopteran eggs in and around release sites. Successful inoculative releases and suppression of corn borer would provide an excellent biologically-based alternative to insecticides. Because corn is planted throughout the northeastern U.S., results of this research will impact the entire region and they will have broad implications for other corn-growing regions and other cropping systems in which ECB is a pest.
OBJECTIVES: 1.Evaluate inoculative releases of Trichogramma ostriniae on ECB populations and damage in field corn in New York, Pennsylvania, Delaware, and Virginia 2.Construct a predator/prey simulation model for T. ostriniae-ECB 3.Investigate the potential overwintering of T. ostriniae in each state 4.Assess possible non-target effects of T. ostriniae releases by evaluating parasitism of other lepidopteran hosts in and around corn fields 5.Determine a cost benefit analysis of the release program
APPROACH: Objective 1. In-field evaluations of T. ostriniae will be made over a two-year study. The states selected for our research study are important producers of field corn in the eastern U.S. (Table 1). The multi-state approach will offer a wide range of climatic conditions and ECB populations to test the efficacy of T. ostriniae. Releases will be made in five fields in each state per year. Objective 2. The European corn borer developmental model (Calvin 1985, Higgins et al. 1986) will be linked to a Trichogramma spp. developmental model (Calvin 1981) to predict the timing of ECB egg deposition periods relative to the adult Trichogramma host searching period and predict optimal release timings. The ECB and Trichogramma models currently predict the proportion of the population in a given life stage at any time during the growing season. Both models are designed as distributed delays to capture the variance in individual developmental rates. Objective 3. The multi-state approach will offer a wide range of climatic conditions and ECB populations to evaluate the overwintering potential of T. ostriniae. Sentinel egg masses (Carlson and Andrew 1976) will be obtained (purchased) from an ECB colony maintained at Cornell University. In the spring of each season following releases at each of the sites, 50 sentinel ECB egg masses will be fastened to corn and other foliage in and around each field. Sentinel egg masses will be retrieved 1 week later and brought back to the laboratory (or shipped to Cornell) for assessment. ECB eggs will be counted and held in gelatin capsules to determine percent parasitism, and percent emergence of T. ostriniae. Objective 4. During weekly sampling for Objective 1, eggs of any lepidopteran hosts found in and around cornfields, such as armyworm, fall armyworm, corn earworm, stalk borer, cutworm, and Monarch butterfly, will be collected and brought back to the laboratory (or shipped to Cornell) for assessment of parasitism. In addition, several host choice experiments using the aforementioned lepidopterans with ECB will be conducted in field cages Objective 5. Data on all inputs (cost of Trichogramma release) and outputs (yield savings based on reduced ECB damage) will be collected from the experiments. Partial budgets will then be prepared that calculate the differences in costs of inputs and profits per acre for T. ostriniae-release corn versus non-release corn. Aggregate economic benefits to the northeastern U.S. will be projected based on expected future adoption of biological control program. The benefits over the next 10 years will be discounted and summed to estimate aggregate benefits to the region. In addition, the results of this analysis will be used to provide NE corn growers with realistic costs and benefits for the following cases: 1) no control of ECB; 2) IPM-based insecticide spraying for ECB; 3) inoculative release of T. ostriniae for ECB control. This information will enable us to determine the profitability of a biological control program for ECB.
PROGRESS: 2001/06 TO 2004/05
We evaluated the egg parasitoid Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)
for control of European corn borer (Lepidoptera: Crambidae) in field corn in
2001 and 2002. Early-season inoculative releases of 75,000 parasitized eggs/ha
were made in New York and Virginia in five to ten cornfields per state. Incidence
of egg mass parasitism, number of stalk tunnels, incidence of ear damage, and
whole-plant yield were evaluated. Parasitism of European corn borer egg masses
ranged from 0 to 75 percent in release plots and was greater in release plots
than in control plots. In 2001, the number of tunnels/100 plants was affected
by the interaction of location (state) and presence of the parasitoid. Comparison
of tunnel number between paired release and control plots showed that of 15
individual comparisons, five fields benefited from T. ostriniae releases. Comparisons
of ear damage between individual paired plots within years showed that in only
one instance was ear damage reduced by T. ostriniae. Although these studies
suggest that T. ostriniae may be a poor candidate for biological control of
European corn borer in field corn, we remain optimistic about their potential.
Higher release rates and better timing of the release may improve performance.
Because of demonstrated success in sweet corn, further studies should be conducted
to evaluate whether adjustments in frequency, timing, and rate of release in
field corn under varying European corn borer pressure will result in economic
control in field corn.
IMPACT: 2001/06 TO 2004/05
Contrary to results from sweet corn, the results of this study suggest that
a single inoculative release of 75,000 T. ostriniae/ha is an unsuitable method
for controlling European corn borer in field corn. Although egg parasitism was
observed in 2001 in both New York and Virginia, plant damage and yield were
unaffected by the presence of T. ostriniae. The conclusions from this research
corroborate the findings of earlier research in which T. ostriniae did not reduce
stalk and ear damage in field corn despite relatively high levels of parasitism
(Wright et al., 2002). However, increased rates of release and improved timing,
especially in areas where European corn borer populations are high, might result
in yield improvement.
PUBLICATIONS: 2001/06 TO 2004/05
Hoffmann, M.P., S.A. Pitcher, J. Gardner, J.E. Losey, T.P. Kuhar, C.A. Laub
and R.R. Youngman. 2004. Efficacy of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)
against European corn borer (Lepidoptera: Crambidae) in field corn. SUBMITTED.
PROJECT CONTACT:
Name: Decker, D. J.
Phone: 607-255-2224
Fax: 607-255-9499
Email: cuaes@cornell.edu