Cultural and Chemical Management of Pumpkin Viruses

Preliminary Report, 12/11/95




Principal Investigator: Celeste Welty, O.S.U. Department of Entomology







Bob Precheur, O.S.U. Dept. of Horticulture & Crop Science
Mac Riedel, O.S.U. Department of Plant Pathology

Other Key Personnel:
Brad Bergefurd, Ag.-Enterprise Center, Hillsboro
Mark Schmittgen, Lane Avenue Horticulture Farm


Background and Objectives of Research:

Mosaic virus diseases vectored by aphids have caused up to 50% yield reduction in some Ohio pumpkin fields during the past few years. Use of reflective mulch, insecticides, stylet oil, and adjusted planting date may prevent or minimize the effects of virus diseases, but these strategies needs to be evaluated before they can be recommended. Our objective was to determine which viruses are infecting Ohio pumpkins, and to evaluate the efficacy of cultural and chemical practices for suppressing virus diseases.

Part 1, Virus Survey:

Pumpkin leaves from 27 farms across Ohio were collected in August to September 1995 and frozen. Virus symptoms were much more common in 1995 than in 1994. Incidence of virus in pumpkin leaves from 27 Ohio farms, August-September 1995, as detected by Elisa tests, is presented in the table below:

Results of Pumpkin Virus Survey, 1995
Number of Positive Samples
per 15 samples tested
DateCountyWMVCMVSMVPRSVZYMVPOTY
South West Ohio
8/11 Warren 15 0 0 1 0 15
8/11 Warren 15 9 0 0 0 14
8/17 Highland 0 0 0 0 0 0
8/17 Pickaway 14 0 2 0 0 14
8/31 Clark 15 2 0 0 0 15
8/31 Greene 15 0 0 1 0 15
8/31 Greene 3 3 0 0 0 3
8/31 Champaign 15 0 0 0 0 15
East and Central Ohio
8/22 Delaware 0 2 0 0 0 0
8/22 Union 15 0 0 0 1 15
8/25 Franklin 15 0 0 0 0 15
8/25 Lickling 15 2 1 0 0 15
9/8 Coshocton 4 0 0 0 0 4
9/8 Coshocton 15 0 1 1 0 15
9/8 Muskingum 15 0 0 0 0 15
9/19 Delaware 1 0 0 0 0 1
North Central Ohio
8/9 Ottawa 0 3 0 0 0 0
8/9 Sandusky 0 0 0 0 0 0
8/9 Sandusky 0 0 0 0 0 0
8/24 Erie 13 0 1 0 0 13
9/14 Huron 15 3 0 0 0 15
North East Ohio
8/15 Geauga 0 0 0 0 0 0
8/15 Geauga 0 0 6 0 0 0
9/6 Portage 0 0 0 0 0 0
9/6 Portage 0 0 0 0 0 0
9/6 Portage 15 2 0 0 0 15
9/6 Summit 12 0 0 9 0 15
Number of farms with positive samples
for each virus		 18 8 5 4 1 18
  • WMV = Watermelon mosac virus (formerly called WMV-2)
  • CMV = Cucumber mosaic virus
  • SMV = Squash mosaic virus
  • PRSV = Papaya ringspot virus (formerly called WMV-1)
  • ZYMV = Zucchini yellow mosaic virus
  • POTY = Potyvirus Group

    • Part 2, Field Experiments:
    In each of the three experiments described below, plants were inspected weekly for aphids; and leaves were collected periodically and frozen until tested by ELISA methods for presence of 5 specific viruses and for generic pot-y virus; and winged aphids were trapped in water pan traps.

    Experiment 1: Reflective Mulch.

    Methods: Reflective mulch is supposed to prevent flying aphids from landing on plants. Two treatments evaluated were: 1) reflective plastic mulch; 2) bare ground with no mulch. There were 5 or 6 replicates at each of 3 sites: Columbus, Hillsboro, Circleville. Plot size was large: 5 rows by 50 ft. All plots were treated with Furadan 4F insecticide at planting for cucumber beetle control.

    Results:At all 3 sites, aphid infestations during the first few weeks after emergence were significantly lower on plants on reflective mulch than in plants on bare ground (Table 1). The effect on aphids was lost once rows filled in and covered the mulch. Harvest data have not yet been analyzed, but there did not appear to be a difference between treatments in the yield of marketable or virus-symptomatic plants.

    Table 1. Aphid Density on Young Pumpkins Grown in Reflective Mulch
    Mean Number per Plant
    SiteDateTreatmentWinged aphidsWingless aphids
    Columbus 6/23/95 bare ground 0.07 a 0.00 a
    reflective 0.00 a 0.00 a
    Columbus 6/29/95 bare ground 0.63 a 0.00 a
    reflective 0.03 b 0.00 a
    Columbus 7/5/95 bare ground 2.03 a 7.2 a
    reflective 0.40 b 1.1 b
    Circleville 6/30/95 bare ground 0.56 a 2.24 a
    reflective 0.04 b 0.00 a
    Circleville 7/6/95 bare ground 13.6 a 63.6 a
    reflective 0.6 b 4.0 b
    Hillsboro 6/23/95 bare ground 2.40 a 11.6 a
    reflective 0.03 b 0.4 b

    Experiment 2, Systemic Insecticides and Planting Date.

    Methods: Four insecticide treatments were evaluated in each of two plantings at one site in Columbus. The early planting was seeded on 6 June and the late planting was seeded on 6 July. Treatments applied at-planting were: 1) carbofuran (Furadan 4F), 2) imidacloprid (Admire 2F), 3) acephate (Payload 15G), and 4) untreated control. Note that neither Admire or Payload are yet registered for use on pumpkins. There were four replicates with small plot size (1 row by 40 ft).

    Results: Aphids successfully colonized plants in all of the treatments; systemic insecticides applied to soil at planting did not provide adequate control. Heavy rainfall in late June may have contributed to lack of efficacy.

    Table 2. Aphid density on young pumpkin plants in systemic insecticide trial, 1995.
    Mean Number per Plant
    PlantingDateTreatmentWinged aphidsWingless aphids
    Early 6/22/95 untreated 0.15 a 0 a
    Furadan 0.05 a 0 a
    Admire 0.35 a 0 a
    Payload 0.20 a 0 a
    Early 6/28/95 untreated 0.20 b 0.05 a
    Furadan 0.45 b 0 a
    Admire 0.85 a 0 a
    Payload 0.25 b 0 a
    Early 7/7/95 untreated 20 a 102 a
    Furadan 12 a 62 a
    Admire 21 a 62 a
    Payload 17 a 101 a
    Late 7/25/95 untreated 0.15 a 1.70 a
    Furadan 0.15 a 3.15 a
    Admire 0.30 a 0.10 a
    Payload 0.10 a 0.80 a
    Late 8/4/95 untreated 5.15 a 47 a
    Furadan 3.45 a 37 a
    Admire 3.20 a 21 a
    Payload 4.20 a 51 a

    Experiment 3, Stylet Oil:

    Two treatments were evaluated at Columbus: 1) stylet oil twice per week from emergence until fruit set then once per week until harvest, plus methomyl weekly from emergence until harvest; 2) methomyl without stylet oil. There were 3 replicates of large plots (8 rows by 80 ft). Data have not yet been analyzed, but we did not observe any reduction in yield of virus symptomatic fruit at harvest.