Research Program on Pumpkin Diseases in Illinois

 

M. Babadoost, S.Z. Islam, D. Tian, C. Pavon and M. Hurt, Department of Crop Sciences, University of Illinois, Urbana-Champaign; J.M. Swiader and H.M. Fouly, Department of NRES, University of Illinois, Urbana-Champaign; M.O. Ogutu, Extension Service, University of Illinois, 6438 Joliet Rd., Countryside, IL; S.A. Walters; Department of Plant, Soil, and General Agriculture, Southern Illinois University, Carbondale, and Y. Honda, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan.

 

Introduction

 

Illinois ranks first in pumpkin production in the nation. Approximately, 12,000 acres of jack-o-lantern and 9,000 to 10,000 acres of processing pumpkins are produced in Illinois. About 90% of processing pumpkins produced in the United States are grown in Illinois. Several diseases, including powdery mildew (Sphaerotheca fuliginea), Phytophthora blight (Phytophthora capsici), downy mildew (Pseudoperonospora cubensis), gummy stem blight and black rot (Didymella bryoniae), Plectosporium blight (Microdochium blight) (Plectosporium tabacinum), Fusarium wilt and fruit rot (Fusarium spp.), Sclerotinia rot (Sclerotinia sclerotiorum), bacterial spot (Xanthomonas campestris pv. cucurbitae), bacterial wilt (Erwinia tracheiphila), and virus diseases including cucumber mosaic virus (CMV), squash mosaic virus (SqMV), watermelon mosaic virus (WMV), zucchini yellow mosaic virus (ZYMV), and papaya rings spot virus (PRSV) occur in pumpkin fields in Illinois, causing up to 100% yield losses. A research program was initiated in 2000 to develop effective methods for management of diseases of jack-o-lantern and processing pumpkins in Illinois. The objectives of this research program are: (i) to evaluate effectiveness of fungicide seed-treatment on controlling seedling death of pumpkins caused by P. capsici in pumpkin fields; (ii) to evaluate effectiveness of fungicide spray application on controlling foliar blight and fruit rot of pumpkins; (iii) to determine the effectiveness of induced plant resistance by red-light treatment on controlling foliar blight and fruit rot caused P. capsici and other diseases of pumpkins; (iv) to assess the effectiveness of calcium application on suppressing P. capsici in the field; and (v) to evaluate the effectiveness of integrated approaches of seed treatment, fungicide spray, red-light treatment and calcium application on controlling pumpkin diseases.

 

The research on management of pumpkin diseases is funded by: Department of Crop Sciences-University of Illinois, Illinois Department of Agriculture, North Central-IPM Program, North Central Region-SARE, Nestle Food Company, BASF Corp., Bayer Corp., Cerexagri Inc., DuPont Corp., Syngenta, and Uniroyal Chemical Co.

 

This research program has already offered effective control of several pumpkin diseases, especially control of the devastating disease caused by P. capsici. This research also has resulted in publishing several papers in peer-reviewed journals, Extension Newsletters, and Websites. The following are some of these publications.

 

1. Babadoost, M. 2000. Outbreak of Phytophthora foliar blight and fruit rot in processing pumpkin fields in Illinois. Plant Dis. 84:1345.

 

2.                  Islam, S.Z., Babadoost, M., and Honda, T. 2002. Effect of red-light treatment of seedlings of pepper, pumpkin, and tomato on the occurrence of Phytophthora damping-off. HortScience 37: 678-681.

3.                  Islam, S.Z., Honda, Y., Babadoost, M. 2002. Antifungal glycoprotein in red-light irradiated broadbean leaflets. Mycoscience 43:471-473.

 

4.                  Babadoost, M., and Islam, S. Z. 2002. Phytophthora blight on pumpkin. Plant Health Progress doi:10.1094/PHP-2002-1216-01-DG.

 

5.                  Babadoost, M., and Islam, S.Z. 2003. Fungicide seed treatment effects on seedling damping-off of pumpkin caused by Phytophthora capsici. Plant Dis. 87:63-68.

 

6.                  Islam, S.Z., and Babadoost, M. 2003. Genetic and pathogenic variation among Phytophthora capsici isolates infecting processing pumpkin. Plant Dis. 87 (submitted).

 

7.                  Tian, D., and Babadoost, M. 2003. Host range of Phytophthora capsici from pumpkin and pathogenicity of the isolates. Plant Dis. 87 (submitted).

 

8.                  Babadoost, M. 2000. Incidence and impact of Phytophthora diseases. Illinois State Hort. Soc. Summer Orchard Day 2000: 22-25.

 

9.                  Babadoost, M., and Islam, S.Z. 2001. Studies on chemical control of Phytophthora blight of processing pumpkins. 2001 Processing Crops Manual and Proc. Midwest Food Processors Assoc. 2001: 69-177.

 

10.              Babadoost, M. 2002. Evaluation of selected fungicides to control jack-o-lantern pumpkin diseases. 2002 Processing Crops Manual and Proc. Midwest Food Processors Assoc. 2002:145-251.

 

11.              Babadoost, M. 2002. Cucurbit and cucurbit diseases in Illinois. The 46th Ann. Agronomy Day, UI 2002: 39.

 

12.              Babadoost, M. 2002. Management of Phytophthora blight of cucurbit crops in Illinois. Cucurbitaceae 2002, Phytophthora capsici Symposium:31-32. Naples, FL.

 

13.              Babadoost, M., and Islam, S.Z. 2001. Evaluation of fungicides for control of Phytophthora blight of processing pumpkin, 2000. Fung. & Nemat. Tests 56:V65.

 

14.              Babadoost, M. 2001. Phytophthora Blight of Cucurbits (Fact Sheet, RPD), 3 pp. http://www.aces.uiuc.edu/vista/abstracts/a945.html.

 

15.              Babadoost, M. 2002. Website: http://veg-fruit.cropsci.uiuc.edu.

 

 

 

 

Research Projects on Management of Pumpkin Diseases

 

I. Control of Phytophthora Blight of Pumpkins by Fungicide Spray

 

M. Babadoost and S. Z. Islam, Department of Crop Sciences, University of Illinois, Urbana-Champaign.

 

Prior to 2001, there was no method available to provide adequate control of P. capsici in pumpkin fields in Illinois. The common practice for reducing the incidence of this disease in vegetable fields has been an integrated approach combining long-term crop rotation, sanitation, and management of field moisture. This approach does not provide adequate protection to crops against P. capsici because: (i) the pathogen survives in the soil indefinitely, and (ii) in the areas with high relative humidity and/or rainfall, management of field moisture is not feasible. No resistant pumpkin variety is available. Other practices including amending soil, using cover crops, straw mulching, soil solarization, and using antagonistic fungi for protecting crops in the fields have been investigated, but none of them have provided adequate protection in cucurbits against P. capsici. In some areas, fungicides have been used to reduce the incidence of Phytophthora diseases of vegetables.

 

During 2000-2001, we tested more than 30 fungicides with potential effect on Phytophthora species to evaluate their effectiveness on controlling P. capsici on pumpkins. Extensive tests were carried out in the laboratory, greenhouse, and fields. As a result, we recommended using dimethomorph (Acrobat) for controlling foliar blight and fruit rot of pumpkins caused by P. capsici. We obtained permission from USEPA under section 18 permission of FIFRA for the use of dimethomorph (Acrobat) for foliar spray to control foliage blight and fruit rot caused by P. capsici in cucurbit fields in 2001 and 2002. In the fall of 2002, this compound was registered for the use on cucurbit crops. However, only five spray applications of Acrobat are permitted during a growing season. Thus, this approach was a short-term solution for saving pumpkin industry from the devastating Phytophthora disease. There is definitely an urgent need for development of long-term strategies for management of Phytophthora diseases in pumpkins, as well as other vegetables, in Illinois.

 

Five applications of dimethomorph (6.4 oz Acrobat 50WP/acre) plus copper sulfate (2.5 lb Cuprofix Disperss/acre), at a weekly schedule, provide effective protection against foliar blight and fruit rot, caused by P. capsici, in pumpkin fields. Application of the fungicides begins at the first sign of the disease. In 2002, fungicide spray reduced yield losses from 100% to less than 10% in the commercial fields.

 

 

II. Fungicide Seed Treatment Effects on Seedling Damping-Off of Pumpkin Caused by Phytophthora capsici.

 

M. Babadoost and S.Z. Islam, Depart. of Crop Sciences, Univ. of Illinois, Urbana-Champaign.

 

Phytophthora blight, caused by the Oomycete plant pathogen Phytophthora capsici, is an important disease of cucurbits, eggplants, peppers, and tomatoes. The incidence of this disease has increased in recent years in the United States and worldwide. P. capsici survives as oospores in soil and as mycelium in plant residue. The pathogen can infect all parts of the plant at any growth stage, causing pre- and post-emergence seeding damping-off, leaf spot, stem lesion, foliar blight, and fruit rot. No cucurbit cultivar with measurable resistance against Phytophthora blight is available. The objective of this study was to develop a fungicide seed-treatment for control of seedling death of pumpkins caused by P. capsici.

 

Seed treatment with mefenoxam (0.65 fl oz Apron XL LS/100 lb seed) and metalaxyl (1.5 fl oz Allegiance FL/100 lb seed) significantly reduced pre- and post-emergence damping-off of seedlings caused by P. capsici in three pumpkin cultivars, Dickinson, Hybrid-401, and Hybrid-698, tested. Thirty-one days after seeding, at inoculum levels of 0, 90, 600, 1400, and 4000 cfu/g soil, the average seedling stands for Apron treatment were 98.4, 93.8, 88.3, 77.8, and 64.8%; for Allegiance, were 99.1, 85.3, 85.8, 73.5, and 59.3; and for the untreated control were 97.5, 55.2, 45.7, 37.0, and 22.9%, respectively. In field trials, the average seedling stands 35 days after seeding were 76.7, 74.7, and 44.9% for Apron, Allegiance, and untreated control, respectively. Seed treatment with Apron or Allegiance did not have any significant effect on either seed germination or seedling vigor. The integration of seed treatment with Apron or Allegiance with foliar spray of plants with Acrobat provides satisfactory protection of pumpkin plants against P. capsici during the 4-month growing season.

 

 

III. Effect of Red-Light Treatment of Seedlings of Pumpkin, Pepper, and Tomato on the Occurrence of Phytophthora Damping-off

 

S. Z. Islam and M. Babadoost, Department of Crop Sciences, University of Illinois, Urbana-Champaign; and Y. Honda, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan.

 

A study was conducted in the greenhouse to investigate the effects of red light (600-700 nm) on the subsequent occurrence of seedling infection of bell pepper, pumpkin, and tomato caused by Phytophthora capsici. Three- or four-week-old seedlings were inoculated with zoospores or transplanted into pots filled with artificially infested soil mix. Red-light treatment of seedlings reduced Phytophthora damping-off by up to 79%. Only 21 to 36% of red light treated seedlings became infected, whereas 78 to100% of the control seedlings, grown either in natural daylight (NDL) or under white light (WL), became infected and died. The height, fresh and dry weight of seedlings treated with red light were significantly higher than those grown under NDL or WL.

 

 

IV. Determining Host Range of Phytophthora capsici from Pumpkin and Pathogenicity of Isolates

 

D. Tian, and M. Babadoost; Depart. of Crop Sciences, Univ. of Illinois, Urbana-Champaign

 

This study was conducted to determine host range of Phytophthora capsici isolates from pumpkin and virulence of the isolates on pumpkin cultivars. The pathogenicity of P. capsici isolates from pumpkin was evaluated on 45 species of herbaceous plants, including 36 species of crops grown in rotation sequences with pumpkin and nine species of weeds that commonly grow in pumpkin fields in Illinois. Plants were grown in the greenhouse and 4-wk-old seedlings were inoculated by adding 5 ml of a zoospore suspension (2 x 105 spores/ml of water) onto soil surface around stem of each plant in the pot. Twenty-two crop species and two weed species became infected with P. capsici and developed symptoms. Phytophthora capsici was re-isolated from all of the symptomatic plants by culturing tissues on a semi-selective medium (PARP). Also, P. capsici was detected in 87.5% of infected plants by a PCR method using PCAP and ITS5 primers. Cucurbits and peppers were the most susceptible hosts of P. capsici. Five crop species/variety, beet (Beta vulgaris), Swiss chard (Beta vulgaris var. cicla), lima beans (Phaseolus lunatus), turnip (Brassica rapa), and spinach (Spinacia olerace), and one weed species, velvet leaf (Abutilon theophrasti), were found hosts of P. capsici for the first time. Six isolates of P. capsici were inoculated onto six pumpkin cultivars (three processing and three jack-o-lantern pumpkins) in the greenhouse and found significantly isolate cultivar interactions. Phytophthora capsici isolates were more virulent on jack-o-lantern pumpkins than processing pumpkins.

 

 

V. Pathogenic Variation in Phytophthora capsici Isolates from Processing Pumpkin in Illinois

 

S.Z. Islam, M. Babadoost, and K. Lambert, Department of Crop Sciences, University of Illinois, Urbana-Champaign; H.M. Fouly, Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana-Champaign.

 

This study investigated genetic, pathogenic, and morphological variation among Phytophthora capsici isolates from processing pumpkin in Illinois. Random amplified polymorphic DNA (RAPD) markers were employed to assess genetic variation among 15 isolates of P. capsici from 15 individual fields at five locations. Unweighted mean pair group analysis clustered isolates into five groups. The genetic distances ranged from 0.17 to 0.36. Inoculation of pumpkin seedlings in the greenhouse revealed that isolates belonging to distinct genetic groups differed significantly (P = 0.05) in aggressiveness. Isolates of P. capsici tested exhibited four growth patterns: cottony, rosaceous, petaloid, and stellate. Isolates of P. capsici, including an ATCC isolate (ATCC-15427), having cottony growth pattern could not grow at 36C. The mean oospore diameter in A1 mating type isolates was greater than that of A2 mating types. Five of 20 isolates tested produced chlamydospores in V8-CaCO3 liquid medium. This is the first report of chlamydospore formation of cucurbit isolates of P. capsici.

 

 

VI. Pathogenic and Genetic Variation of Phytophthora capsici isolates from Illinois

D. Tian, and M. Babadoost; Depart.of Crop Sciences, Univ. of Illinois, Urbana-Champaign.

The objective of this study was to investigate genetic and pathogenic variation among P. capsici isolates from Illinois. Phytophthora capsici isolates were collected from various hosts and locations in Illinois. The rate of colony growth, morphology of sporangia, and pathogenicity of the isolates were investigated. There were significant differences in the rate of colony growth among the isolates. Also, length, breath, length/breath ratio, and length of pedicels of sporangia of the isolates differed significantly. Pathogenicity test in the greenhouse showed that P. capsici isolates from pumpkin were significantly less aggressive on eggplant than they were on cucurbits, pepper, and tomato. Three pathogenicity groups were determined among the isolates from different locations. No significant relationship between pathogenicity of the isolates and original hosts was found. Genetic variation among the isolates was studied using internal transcribed spacer (ITS) regions of rDNA, inter simple sequence repeat (ISSR), and amplified fragment length polymorphism (AFLP) methods. No significant difference was detected in ITS regions of the isolates. ISSR and AFLP tests showed genetic variation among the isolates. Cluster analysis separated the isolates into three distinct groups, based on the locations that they had been collected. It was concluded that isolates of P. capsici from different regions of the state differ in genetic combination and virulence.

 

 

VII. Integrated Management of Pumpkin Diseases

 

M. Babadoost, S.Z. Islam, and M. Hurt Department of Crop Sciences, University of Illinois, Urbana-Champaign; J.M. Swiader, Department of NRES, University of Illinois, Urbana-Champaign; M.O. Ogutu, Extension Service, University of Illinois, 6438 Joliet Rd., Countryside, IL; and S.A. Walters, Department of Plant, Soil, and General Agriculture, Southern Illinois University, Carbondale.

 

A research study is underway in a commercial pumpkin field at Pekin, IL, to determine the most effective integrated management of pumpkin diseases. Integrated approaches of seed treatment, fungicide spray (11 fungicides), calcium application (soil and plant), and using induced plant resistance (red light and chemical) on controlling pumpkin diseases (with emphasis on Phytophthora blight) are being investigated. The trial includes 30 treatments arranged in a completely randomized block design with 3 replications. Weekly data on the incidence and severity of diseases are collected and the results will be available at the end of the season.

 

 

VIII. Evaluating Efficacy of Selected Fungicides on Controlling Jack-O-Lantern Pumpkin Diseases, Champaign, IL

 

M. Babadoost and M. Hurt Depart. of Crop Sciences, Univ. of Illinois, Urbana-Champaign

 

In 2003, a field trial is being conducted at the University of Illinois Vegetable Research Farm at Champaign, IL, to evaluate the efficacy of selected fungicides on controlling diseases of jack-o-lantern pumpkin.