White yarrow and feverfew were tested as companion plants with summer squash for control of squash bug. Companion planting with white yarrow had few effects. Companion planting with feverfew tended to reduce squash bug populations, but plot-to-plot variation was high and results often were not statistically significant. Early-season row covers (without herbs) neither reduced squash bug populations nor increased squash yields. Herbs reduced marketable squash yields compared to the control only once out of seven experiments. The tested companion planting strategies inconsistently affected squash bug populations on summer squash. Therefore, these strategies are not recommended to commercial producers.
The economic value of the various cucurbit crops produced in the southern United States is very high. Government statistics of the value of these crops, however, are no longer available on a regional basis. In Oklahoma, the 2007 Census of Agriculture showed a total of over 5,000 acres of cucurbit production. Using estimated average crop values per acre (Smith and Ancisco, 2005), this production was worth over $11.7 million.
Vegetable producers in Oklahoma have identified pest control issues as a major concern during Cooperative-Extension-facilitated listening sessions. For cucurbits, the single most important insect pest is the squash bug, Anasa tristis DeGeer. Squash bug management typically involves multiple applications of chemical insecticides (Bolin and Brandenberger, 2001; Kemble, 2012). There is considerable qualitative information regarding this insect (e.g., the review of Beard, 1940), but more quantitative data are needed. In particular, the scientific literature contains very little information about non-insecticidal approaches to squash bug management.
The concept of companion planting as a potential pest management tool has received some attention recently as interest in sustainable and organic vegetable production has grown. Example studies include: Issa et al., 2012; Moreau et al., 2006; Finch et al., 2003; Morris and Li, 2000; and Latheef and Ortiz, 1984. Results have been mixed, and none of these studies has addressed squash bug management. This project was designed to provide information on the potential of companion plants as tools for pest management of squash bug in commercial production of summer squash.
There are many possibilities for companion plants, both as resource plants for beneficial insects and as pest insect repellents. To narrow the choices, we began with information in Yepsen Jr. (1976) suggesting that tansy and nasturtium would repel squash bugs. Next, we examined the one journal article we found on companion planting for insect control in cucurbits (Cline et al., 2008). They reported that the combined use of three companion plants reduced populations of cucumber beetles in muskmelons in one year. The plants were radish (Raphanus sativus L.), tansy (Tanacetum vulgare L.), and nasturtium (Tropaeolum majus L.). However, Cline et al. (2008) did not subsequently study nasturtium due to low rates of survival and vegetative growth. Radish was deemed unsuitable for our study because it would not thrive during the Oklahoma summer when squash was growing. Tansy also was removed from consideration, as it can become a large plant and it is considered a noxious weed in four western states (APHIS, 2012). We then looked for information on alternative species related to tansy. Yepsen Jr. (1976) had recommended yarrow (Achillea millefolium L.) as being “more manageable than tansy” and as having a generally repellent effect on pest insects. Yarrow also was reported to help attract and retain predacious and parasitoid arthropods in an apple orchard (Bostanian et al., 2004). Finally, we found a study where feverfew [Tanacetum parthenium (L.) Sch. Bip.] was found to be a “banker” plant that could attract and maintain high populations of predatory insects (Lopez and Shepard, 2007). Therefore, we chose yarrow and feverfew as the test species for our study.
APHIS. 2012. Federal Noxious Weed List. Online @ http://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/weedlist.pdf. Accessed 18 Oct. 2012.
Beard, R.L. 1940. The biology of Anasa tristis DeGeer with particular reference to the tachinid parasite, Trichopoda pennipes Fabr. Conn. Agr. Exp. Sta. Bul. 440.
Bolin, P. and L. Brandenberger. 2001. Cucurbit integrated crop management. Coop. Ext. Serv., Okla. State Univ., Stillwater. E-853.
Bostanian, N.J., H. Goulet, J. O’Hara, L. Masner, and G. Racette. 2004. Towards insecticide free apple orchards: Flowering plants to attract beneficial arthropods. Biocontrol Science and Technology 14:25-37.
Cline, G.R., J.D. Sedlacek, S.L. Hillman, S.K. Parker, and A.F. Silvernail. 2008. Organic management of cucumber beetles in watermelon and muskmelon production. HortTechnology 18:436-444.
Finch, S., H. Billiald, and R.H. Collier. 2003. Companion planting – do aromatic plants disrupt host-plant finding by the cabbage root fly and the onion fly more effectively than non-aromatic plants? Entomol. Exper. Appl. 109:183-195.
Issa, R.B., L. Gomez, M.H. Sauge, and H. Gautier. 2012. Effects of companion plants on the behavior of the green peach aphid reared on pepper plants. IOBC/WPRS Bulletin 75:29-33.
Kemble, J.M. (ed.). 2012. Southeastern U.S. 2012 Vegetable Crop Handbook. Online @ http://www.thegrower.com/south-east-vegetable-guide. Accessed 5 Nov. 2012.
Latheef, M.A. and J.H. Ortiz. 1984. Influence of companion herbs on Phyllotreta cruciferae (Coleoptera: Chrysomelidae) on collard plants. J. Econ. Entomol. 77:80-82.
Lopez, R. and B.M. Shepard. 2007. Arthropods associated with medicinal plants in coastal South Carolina. Insect Sci. 14:519-524.
Moreau, T.L., P.R. Warman, and J. Hoyle. 2006. An evaluation of companion planting and botanical extracts as alternative pest controls for the Colorado potato beetle. Biol. Agr. Hort. 23:351-370.
Morris, M.C. and F.Y. Li. 2000. Coriander (Coriandrum sativum) “companion plants” can attract hoverflies, and may reduce pest infestation in cabbages. New Zealand J. Crop Hort. Sci. 28:213-217.
Smith, D.T. and J. L. Ancisco. 2005. The Crops of Texas. Dept. Tech. Report SCS-2005-01. Dept. of Soil and Crop Sciences, Texas A&M Univ.
Yepsen Jr., R.B. (ed.). 1976. Organic plant protection. Rodale Press, Emmaus, PA.
- Provide on-farm-research-based information on the potential of companion plants as tools for pest management of squash bug in commercial production of summer squash.
- Demonstrate sustainable squash production systems to producers and provide education in the newly-developed pest management systems.
Trials were conducted at the Cimarron Valley Research Station in Perkins, Payne County, OK and in two producers’ fields (J. Motes and W. Whitmore) about 25 miles apart in Payne County, OK. ‘Lioness’ yellow straightneck summer squash was seeded in peat-lite mix in individual peat pots in an on-campus greenhouse about 10 days before scheduled field planting. We began with three to four seedlings per pot and thinned to the two strongest plants per pot after field establishment was confirmed. Herb transplants were obtained from a commercial supplier. The basic field production protocol consisted of companion plants transplanted in double rows. The double rows were about 20” apart and spaced on 6’ centers, with surface drip irrigation. This allowed one peat pot containing two squash plants to be transplanted in the middle of each pair of companion plants. Spacing between plants within the rows was 18”. Plots were watered and fertilized according to normal grower practice. Weeds in the rows were controlled manually, except at the Motes location where black plastic mulch was used. One experimental unit consisted of ten squash plants and ten companion plants (see Figure 1). There were 10’ between experimental units to keep treatments isolated from each other. The design was a randomized complete block with 3 (2013) or 4 (2014 and 2015) replications. Given two test species of companion plants without row covers, a treatment with no companion plants but with an early-season row cover, and a control with no companion plants and no row cover, there were 16 experimental units in each field after 2013, meaning 160 squash plants were available for monitoring and data collection per location.
Field planting dates and harvest periods:
Perkins 2013: Planted 13 May. Harvested 24 June – 9 Aug.
Motes 2014: Planted 13 May. Harvested 9 June – 16 July
Whitmore 2014: Planted 15 May. Harvested 13 June – 9 July
Perkins 2014: Planted 16 May. Harvested 20 June – 19 July
Motes 2015: Planted 18 May. Harvested 21 June – 6 July
Whitmore 2015: Planted 19 May. Harvested 15 June – 16 July
A capstone study was conducted in 2015 at the Cimarron Valley Research Station. This was the only study that deviated from the plot design shown in Figure 1. This study included a squash-only control identical to the plot design used in the other studies. Treatments were a 2 x 2 factorial arrangement of herb planting time (either 26 Apr. = “early” or 12 May = the same day as the squash planting) and squash/herb row arrangement (either one row of squash and two rows of herbs as shown in Fig. 1, or a reversal with one row of herbs in the middle of the plot and two rows of squash on the outside). All companion planting treatments had a total of 10 squash plants and 10 herb plants per experimental unit, regardless of planting time or row arrangement. The design was a randomized complete block with 4 replications, resulting in 20 experimental units in the field.
Squash fruit were harvested at least three times a week. Harvested fruits were visually graded, counted, and weighed and data recorded. Squash bug populations were sampled weekly during the growing season, beginning within one week of field planting. Each experimental unit (plot) was sampled by examining all ten squash plants per plot for adult squash bugs and nymphs. The number of adult squash bugs and nymphs per plot was recorded and treatment means were statistically compared across the study.
A pilot study was performed at the Cimarron Valley Research Station in Perkins, OK in 2013, before this grant was funded. None of the treatments gave a statistically significant reduction in squash bugs at Perkins in 2013 (Fig. 2)Figures_edited. The feverfew came close, reducing total (adult plus juvenile) squash bugs by 48% compared to the control.
Companion planting with feverfew reduced total squash bugs compared to the control across the monitoring period at two of three sites in 2014 (Fig. 3). Companion planting with white yarrow reduced total squash bugs compared to the control across the monitoring period at one site in 2014 (Fig. 3). Counts of adult bugs often were low, especially at Perkins, so differences were primarily due to juveniles. The row cover treatment failed at Perkins in 2014; excessive humidity developed under the covers and many squash plants died from the fungus Pythium. Squash grown with yarrow companion plants gave lower marketable fruit weights per acre than control squash at Perkins in 2014 (Table 2).
At Perkins in 2015, the four treatments involving companion planting with feverfew reduced total squash bugs by an average of 48% compared to the control, but statistical significance could not be shown (Table 1)Table 1 Perkins 2015 bugs. The three on-farm treatments also did not affect squash bug populations at either site in 2015 (Fig. 4).
Herbs reduced marketable squash yields compared to the control only once out of seven experiments (yarrow at Perkins in 2014) (Tables 2 and 3)Tables 2 and 3 squash yields. Squash plants eventually overwhelmed herb plants in most cases, although herbs often survived. Planting herbs two weeks ahead of the squash (Perkins, 2015) led to more robust herb plants, but required an extra day in the field and did not affect squash bug populations.
Companion planting with white yarrow had few effects. This herb also proved difficult to kill at the Whitmore farm after the squash crop was finished. Companion planting with feverfew showed a tendency to reduce squash bug populations, but results often were not statistically significant. Plot-to-plot variation was high for squash bug data, making it difficult to detect statistically significant differences. The early-season row covers neither reduced squash bug populations nor increased squash yields.
Educational & Outreach Activities
A demonstration/field day was held at the Motes farm on 7 July 2014, with about 30 clientele attendees. A field day was not held in 2015 due to record rainfall. Plots at the Cimarron Valley Research Station were available for daily viewing by the public each year during regular business hours. The research was featured in one episode in 2013 and again in another episode in 2015 on the Cooperative-Extension-produced television show Oklahoma Gardening. Results were discussed as part of the Vegetable Trial Report in 2014 and 2015. The Vegetable Trial Report (MP-164), edited by one of the collaborators (Dr. Brandenberger), is an outreach publication produced annually in January, and available both in hard copies and in electronic format (see the master link below). Results also were shared with clientele at the Oklahoma-Arkansas Horticulture Industries Show (HIS), an outreach event held in Tulsa on 8 Jan. 2016. There were 319 people registered for HIS. There will be a report in the published proceedings of the HIS later this year. Results were shared regionally and nationally through a poster presentation at the annual meeting of the Southern Region – American Society for Horticultural Science (SR-ASHS), held in San Antonio, TX on 5-7 Feb. 2016. The abstract of this poster presentation is expected to be published in HortScience in September 2016. Ultimately, it is anticipated that the results will be published in a refereed journal article.
Links to outreach products:
Oklahoma Gardening website: http://oklahomagardening.okstate.edu
The Oklahoma Gardening television show has over 170,000 viewers on Saturday and Sunday. The show also has content on Facebook, YouTube, and Twitter.
Oklahoma Gardening 2013 episode: https://www.youtube.com/watch?v=I2mPz9HFly4
Oklahoma Gardening 2015 episode: https://www.youtube.com/watch?v=faNydrWH5-o
Vegetable Trial Reports for 2014 and 2015:
The concept of companion planting as a potential pest management tool has received some attention recently as interest in sustainable and organic vegetable production has grown. Results have been mixed, and we found no studies that addressed squash bug management using companion planting. This project provided scientific information on the potential of companion plants (white yarrow and feverfew) as tools for pest management of squash bug in commercial production of summer squash. There were several positive outcomes. The planting configuration of herb borders on each side of a central squash row (see Fig. 1) was not difficult to implement and did not interfere with subsequent care or harvest of the squash plants. The herb companions required no additional inputs beyond those given to the squash. Herbs reduced marketable squash yields compared to the control only once out of seven experiments. Therefore, this companion planting configuration was promising for future studies. However, companion planting with white yarrow had few effects overall. Companion planting with feverfew showed a tendency to reduce squash bug populations, but results often were not statistically significant. The early-season row covers neither reduced squash bug populations nor increased squash yields. Overall, the project results did not support recommending the tested strategies for squash bug management in commercial production of summer squash.
See the Publications/Outreach section for details of outreach activities.
A demonstration/field day was held at the Motes farm on 7 July 2014, with about 30 clientele attendees.
The Oklahoma Gardening television show has over 170,000 viewers on Saturday and Sunday. The show also has content on Facebook, YouTube, and Twitter. On Facebook, the show generates 1.2 million impressions on more than 565,000 users. Combined annual views per year on YouTube exceed 2.4 million.
Impact of the Vegetable Trial Report cannot be measured directly. At least 50 paper copies were distributed at the Oklahoma-Arkansas Horticulture Industries Show (HIS) in Tulsa on 8 Jan. 2016. There were 319 people registered for HIS and the audience for the project-specific presentation was estimated at 40.
The abstract of the poster presentation is expected to be published in HortScience in September 2016. HortScience is one of three refereed journals published by the American Society for Horticultural Science and it has an international circulation.
Since the tested companion planting strategies inconsistently affected squash bug populations on summer squash, these strategies are not recommended to commercial producers. The project provided scientific information on a topic where little or no such information previously existed. If producers wish to test companion planting on their own, our project demonstrated that the configuration of herb borders on each side of a central squash row was feasible. The early-season row covers neither reduced squash bug populations nor increased squash yields. Row covers still may be useful in summer squash production, but would not be recommended under the specific times of the year and field conditions tested under our project.
Areas needing additional study
There are limited scientific studies on companion planting as a tool for insect pest management in commercial vegetable production. Successful outcomes would increase sustainability. Consideration should be given to methods for screening of potential crop-companion-pest combinations. It should be possible to screen for possible protective or repellent effects of specific herbs or other companion plants to specific pests under controlled conditions. However, laboratory results may not translate to the field. One producer commented that he would have adopted our feverfew companion planting technique if we had been able to show enough consistent impact to save him one or two pesticide applications. If there was a desire to build upon the potentially positive effects of feverfew shown in this project, more funding would be needed to allow for a large-scale study with at least two sites and multiple replications per site. Plot-to-plot variation limited the potential to obtain statistically significant results in our project. Counting squash bugs in the field is labor-intensive, as is management of a large-scale squash planting that requires frequent, repetitive hand harvests.