University of California

Effect of common knotweed (Polygonum aviculare) on abundance and efficiency of insect predators of crop pests


Robert L. Bugg
Lester E. Ehler
L. Theodore Wilson

Authors Affiliations

R. L. Bugg was a former graduate student in Entomology at Davis, and is Postdoctoral Fellow and Research Associate at the Department of Entomology, University of Georgia, Coastal Plain Experiment Station, P.O. Box 748, Tifton, GA 31793-0748; L. E. Ehler was Professor of Entomology and Entomologist in the Experiment Station, Department of Entomology, University of California, Davis; L. T. Wilson was Associate Professor of Entomology and Associate Entomologist in the Experiment Station, Department of Entomology, University of California.

Publication Information

Hilgardia 55(7):1-52. DOI:10.3733/hilg.v55n07p052. October 1987.

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Common knotweed, Polygonum aviculare L. (Polygonaceae), a summer annual occurring in agricultural and urban settings in the Sacramento Valley, was attended by numerous predatory and parasitic insects, many of which fed on the exposed floral nectar. Representatives of 36 insect taxa were observed feeding at the flowers; 29 of these groups contain entomophagous species. Other entomophagous insects were associated with a honeydew-producing, host-specific aphid, Aphis avicularis Hille Ris Lambers. Among predators frequently observed feeding at the flowers were bigeyed bugs, Geocoris spp.

Surveys indicated that common knotweed plants harbored higher densities of bigeyed bugs than did hay alfalfa (Medicago sativa L.), prostrate pigweed (Amaranthus graecizans L.), or field bindweed (Convolvulus arvensis L.). Geocoris punctipes (Say) and Collops vittatus (Say), two predators which are also nectarivorous, survived longer when caged on common knotweed as opposed to hay alfalfa, as did G. punctipes caged on common knotweed as opposed to prostrate pigweed. No difference in longevity was found when G. punctipes was caged on common knotweed with flowers and without flowers.

A further study featured replicated monocultural plots of common knotweed, common purslane (Portulaca oleracea L.), prostrate pigweed, and control plots of bare ground, arrayed in a completely randomized design. Common knotweed plots harbored the highest densities of bigeyed bugs, aphidophagous ladybeetles, and total numbers of predators. Tests of predation efficiency yielded mixed results. Predator discovery of simulated prey (dead vinegar flies glued to cards) was higher on common knotweed than on prostrate pigweed foliage. Similar studies employing egg masses of beet armyworm (Spodoptera exigua Hubner) yielded less definitive results, with rates of discovery by predators being higher on both common knotweed and prostrate pigweed than on common purslane, while the former two rates were not significantly different. Recruitment of predatory ants (Tetramorium caespitum L.) to tuna baits was not significantly different among plots containing the three weed species, despite high numbers of ants attending aphid colonies in the common knotweed plots.

In the next experiment, flats of radish (cv “Sparkler” and “Scarlet Globe,” Raphanus sativus L.), maintained amid wild stands of common knotweed harbored higher densities of bigeyed bugs than did flats in nearby stands of other low-growing weeds. No treatment effect on other predators was evident. Egg masses of an armyworm, Pseudaletia unipuncta (Hayworth) (Lepidoptera: Noctuidae), stapled to radish foliage, were damaged or occupied by predators in slightly greater proportions on radish grown amid common knotweed stands.

In another experiment, predator densities and efficiencies were assessed amid commercial organically-grown bell pepper (cv “Yolo Wonder,” Capsicum annuum [L.]) grown in plots with and without common knotweed. Although the weed harbored higher densities of bigeyed bugs than did bare ground afforded by control plots, visual inspection and shake sampling yielded no evidence for increased densities of predators at the immediate bases or on the foliage of pepper plants. On the other hand, studies employing armyworm egg masses showed enhanced predation by bigeyed bugs and other predators at the bases of pepper plants with adjoining common knotweed. Similar studies involving egg masses stapled to foliage of pepper plants failed to indicate a difference. Common knotweed apparently had no effect on crop vigor and yield.

The final experiment involved replicated plots of hay alfalfa (cv “Amador,” having borders of either common knotweed, prostrate pigweed, common purslane, or uncut alfalfa (control). Proportions of vegetational cover in plot borders differed among several weed regimes: knotweed and control plots featured denser cover than pigweed, and these three regimes exceeded purslane. Purslane borders were devastated by the combined action of herbivorous insects and a fungal pathogen, rendering that regime of little interest. Samples taken on the ground beneath border vegetational canopies yielded an effect due to weed regime for Geocoris densities, with pigweed exceeding knotweed, which in turn exceeded control. Data for total predators, including Geocoris, indicated that knotweed exceeded pigweed, which in turn exceeded control. Visual inspection of borders, which detected Geocoris running about on exposed ground, showed knotweed surpassing purslane and pigweed, which were indistinguishable, followed by control. Despite differences observed in borders, vacuum samples from alfalfa portions of plots indicated no effect by weed regime on densities of bigeyed bugs, Nabis spp., Lygus spp., or lycosid spiders. Similarly, counts of Geocoris taken at ground level amid alfalfa, both before and after mowing the crop, failed to show an effect. Based on shake samples, density of Geocoris was higher on pigweed than on knotweed, whereas the converse was true for Orius tristicolor (White). Nonetheless, based on sweepnetting, Orius densities in alfalfa were not different among the four weed regimes. Predation studies involving beet armyworm egg masses glued to apical foliage of alfalfa failed to show differences among weed regimes. Also, studies employing chunks of tuna placed on cards at ground level amid the alfalfa did not yield significant differences in rates of attendance by Geocoris or by pavement ant. Weed regime had no effect on yield of adjoining alfalfa.

Common knotweed, despite its attractiveness to numerous species of entomophagous insects, may have limited use in enhancing biological control on adjoining crops. The weed may provide alternate prey as well as floral resources, and thus represent such a hospitable habitat that some predators may have no tendency to forage on nearby crop plants. Thus, a weed originally selected to provide a complementary resource (nectar) may also inadvertently afford supplementary resources (alternate prey). Alternate prey could conceivably detract from biological control of pests on adjoining crops. Nonetheless, fieldside common knotweed appears to provide favorable habitat for various predators of agricultural importance. At this point, perhaps the weed should be tolerated in many settings, as it may provide breeding sites and reservoirs from which predators might colonize agricultural fields. Further research should involve multiyear studies on manipulation of common knotweed stands to influence microclimate, soil nutrient levels, and quality of the habitat. These could clarify whether this weed may yet be useful in the enhancement of biological control of insect pests.

Literature Cited

Ables J. R., Jones S. L., McCommas D. W. Jr. Response of selected predator species to different densities of Aphis gossypii and Heliothis virescens eggs. Environ. Entomol. 1978. 7:402-4.

Agnew C. W., Sterling W. L., Dean D. A. Influence of cotton nectar on red imported fire ants and other predators. Environ. Entomol. 1982. 11:629-34.

Allen W. W., Smith R. F. Some factors influencing the efficiency of Apanteles medicaginis Muesebeck. Hilgardia. 1958. 28:1-43. DOI: 10.3733/hilg.v28n02p043 [CrossRef]

Altieri M. A., Letourneau D. K. Vegetation management and biological control in agroecosystems. Crop Prot. 1982. 1:405-30. DOI: 10.1016/0261-2194(82)90023-0 [CrossRef]

Altieri M. A., Whitcomb W. H. The potential use of weeds in the manipulation of beneficial insects. HortScience. 1979. 14:12-18.

Atsatt P. R., O’Dowd D. J. Plant defense guilds. Science. 1976. 193:24-29. DOI: 10.1126/science.193.4247.24 [CrossRef]

Bach C. E. Effects of plant diversity and time of colonization on an herbivore-plant interaction. Oecologia. 1980a. 44:319-26. DOI: 10.1007/BF00545235 [CrossRef]

Bach C. E. Effects of plant density and diversity on the population dynamics of a specialist herbivore, the striped cucumber beetle, Acalymma vittata (Fab.). Ecology. 1980b. 61:1515-30. DOI: 10.2307/1939058 [CrossRef]

Benedict J. H. Jr., Cothran W. R. A faunistic survey of Hemiptera-Heteroptera found in northern California hay alfalfa. Ann. Entomol. Soc. Amer. 1975. 68:897-900.

Bisabri-Ershadi B., Ehler L. E. Natural biological control of western yellow-striped armyworm, Spodoptera praefica (Grote), in hay alfalfa in northern California. Hilgardia. 1981. 49:1-23. DOI: 10.3733/hilg.v49n01p029 [CrossRef]

Bugg R. L. Observations on insects associated with a nectar-bearing Chilean tree, Quillaja saponaria Molina (Rosaceae). Pan-Pac. Entomol. 1987. 63:60-64.

Clement S. L., Norris R. F. Two insects offer potential biological control of common purslane. Calif. Agric. 1982. 36(2,3):16-18.

Crepps W. F. Influence of specific non-crop vegetation on the insect fauna of small-scale agroecosystems 1980. p.102. M.S. thesis., Davis: Univ. Calif

Crocker R. L., Whitcomb W. H. Feeding niches of the big-eyed bugs Geocoris bullatus, G. punctipes, and G. uliginosus (Hemiptera: Lygaeidae: Geocorinae). Environ. Entomol. 1980. 9:508-13.

De Lima J. O. G. Biology of Geocoris pallens Stal on Selected Cotton Genotypes 1980. p.57. Ph.D. diss., Davis: Univ. Calif

De Lima J. O. G., Leigh T. F. Effect of cotton genotypes on the western bigeyed bug (Heteroptera: Miridae (sic)). J. Econ. Entomol. 1984. 77(4):898-902.

Dempster J. P. Some effects of weed control on the numbers of the small cabbage white (Pieris rapae L.) on brussels sprouts. J. Appl. Ecol. 1969. 6:339-45. DOI: 10.2307/2401547 [CrossRef]

Dunbar D. M. The biology and ecology of Geocoris atricolor Montandon, G. pallens Stal, and G. punctipes (Say) 1967. p.99. Ph.D. diss., Davis: Univ. Calif

Duncan D. B. Multiple range and multiple F-tests. Biometrics. 1955. 11:1-42. DOI: 10.2307/3001478 [CrossRef]

Ehler L. E. Natural enemies of cabbage looper on cotton in the San Joaquin Valley. Hilgardia. 1977. 45:73-106. DOI: 10.3733/hilg.v45n03p073 [CrossRef]

Ehler L. E., Miller J. C. Biological control in temporary agroecosystems. Entomophaga. 1978. 23:207-12. DOI: 10.1007/BF02373094 [CrossRef]

Ellington J., George A. P., Kempen H. M., Kerby T. A., Moore L., Taylor B. B., Wilson L. T. Integrated Pest Management for Cotton in the Western Region of the United States. 1985. 3305: Oakland: Univ. Calif. Div. Agric. Nat. Resour. Publ. 144p.

Epstein E. Mineral Nutrition of Plants: Principles and Perspectives. 1972. New York: John Wiley and Sons. 412p.

Eveleens K. G., van den Bosch R., Ehler L. E. Secondary outbreak induction of beet armyworm by experimental insecticide applications in cotton in California. Environ. Entomol. 1973. 2:497-503.

Fischer B. B., Lange A. H., McCaskill J., Crampton B., Tabraham B. Growers Weed Identification Handbook. 1978. Oakland: Univ. Calif. Div. Agric. Nat. Resour. Publ. 4030p.

Foster M. A., Ruesink W. G. Influence of flowering weeds associated with reduced tillage in corn on a black cutworm (Lepidoptera: Noctuidae) parasitoid, Meteorus rubens (Ness von Esenbeck). Environ. Entomol. 1984. 13:664-68.

Fye R. E. Cotton pest and predator reservoirs in Avra Valley. Prog. Agric. Ariz. 1972. 24(6):15-16.

Gonzalez D., Patterson B. R., Leigh T. F., Wilson L. T. Mites: A primary food source for two predators in San Joaquin Valley Cotton. Calif. Agric. 1982. 36(2,3):18-20.

Hagen K. S., Hale R., Maxwell F. G., Harris F. A. Increasing natural enemies through use of supplementary feeding and non-target prey. Proceedings of the Summer Institute on Biological Control of Plant Insects and Diseases. 1974. Jackson: Univ. Press of Mississippi. p. 170-81.

Horn D. J. Effect of weedy backgrounds on colonization of collards by green peach aphid, Myzus persicae, and its major predators. Environ. Entomol. 1981. 10:285-89.

Horn D. J. Vegetational complexity and parasitism of green peach aphids (Myzus persicae (Sulzer) (Homoptera: Aphidae)) on collards. J. New York Entomol. Soc. 1984. 92:19-26.

Kareiva P., Denno R. F., McClure M. S. Influence of vegetation texture on herbivore populations: Resource concentration and herbivore movement. Variable Plants and Herbivores in Natural and Managed Systems. 1983. New York: Academic Press. p. 259-89.

Kliesiewicz J. M., Clement S. L., Norris R. F. Black stem: A fungal disease of common purslane in California. Plant Dis. 1983. 67:1162 DOI: 10.1094/PD-67-1162 [CrossRef]

Knuth P. Handbook of Flower Pollination (Based Upon Hermann Muller’s Work, The Fertilisation of Flowers by Insects) 1908. p.703. Vol. II. Observations on Flower Pollination Made in Europe and the Arctic Regions, on Species Belonging to the Natural Orders Ranunculaceae to Stylidiae. (J. R. Ainsworth Davis, Transl.) Clarendon Press, Oxford, U.K

Leius K. Influence of food on fecundity and longevity of adults of Itoplectis conquisitor (Say) (Hymenoptera: Ichneumonidae). Can. Entomol. 1961a. 93:771-80.

Leius K. Influence of various foods on fecundity and longevity of adults of Scambus buolianae (Htg.) (Hymenoptera: Ichneumonidae). Can. Entomol. 1961b. 93:1079-84. DOI: 10.4039/Ent931079-12 [CrossRef]

Leius K. Effects of pollens on fecundity and longevity of adult Scambus buolianae (Htg.) (Hymenoptera: Ichneumonidae). Can. Entomol. 1963. 95:202-7. DOI: 10.4039/Ent95202-2 [CrossRef]

Leius K. Influence of wild flowers on parasitism of tent caterpillar and codling moth. Can. Entomol. 1967a. 99:444-46. DOI: 10.4039/Ent99444-4 [CrossRef]

Leius K. Food sources and preferences of adults of a parasite, Scambus buolianae (Hym.: Ichn.), and their consequences. Can. Entomol. 1967b. 99:865-71. DOI: 10.4039/Ent99865-8 [CrossRef]

Leon J. A., Tumpson D. B. Competition between two species for two complementary or substitutable resources. J. Theor. Biol. 1975. 50:185-201. DOI: 10.1016/0022-5193(75)90032-6 [CrossRef]

Murdoch W. W., Chesson J., Chesson P. L. Biological control in theory and practice. Am. Nat. 1985. 125:344-66. DOI: 10.1086/284347 [CrossRef]

Naranjo S. E., Stimac J. L. Development, survival, and reproduction of Geocoris punctipes (Hemiptera: Lygaeidae): Effects of plant feeding on soybean and associated weeds. Environ. Entomol. 1985. 14:523-30.

Naranjo S. E., Stimac J. L. Plant influences on predation and oviposition by Geocoris punctipes (Hemiptera: Lygaeidae) in soybeans. Environ. Entomol. 1987. 16:182-89.

Neter J., Wasserman W. Applied Linear Statistical Models: Regression, Analysis of Variance, and Experimental Designs. 1974. Homewood, Ill: Richard D. Irwin, Inc. 842p.

Norris R. F. Weeds and integrated pest management systems. HortScience. 1986. 21:402-10.

Pellett F. C. American Honey Plants. 1976. Hamilton, Ill: Dadant and Sons. 467p.

Pollard E. Hedges VI. Habitat diversity and crop pests: A study of Brevicoryne brassicae and its syrphid predators. J. Appl. Ecol. 1971. 5:109-23. DOI: 10.2307/2401277 [CrossRef]

Rakickas R. J., Watson T. F. Population trends of Lygus spp. and selected predators in strip-cut alfalfa. Environ. Entomol. 1974. 3:781-84.

Rapport D. J. Optimal foraging for complementary resources. Am. Nat. 1980. 116:324-46. DOI: 10.1086/283631 [CrossRef]

Readio J., Sweet M. H. A review of the Geocorinae of the United States east of the 100th meridian (Hemiptera: Lygaeidae). Misc. Publ. Entomol. Soc. Amer. 1982. 12(3):1-91.

Risch S. J. The population dynamics of several herbivorous beetles in a tropical agroecosystem: The effect of intercropping corn, beans, and squash in Costa Rica. J. Appl. Ecol. 1980. 17:593-612. DOI: 10.2307/2402639 [CrossRef]

Risch S. J. Insect herbivore abundance in tropical monocultures and polycultures: an experimental test of two hypotheses. Ecology. 1981. 62:1325-40. DOI: 10.2307/1937296 [CrossRef]

Risch S. J., Andow D., Altieri M. A. Agroecosystem diversity and pest control: Data, tentative conclusions, and new research directions. Environ. Entomol. 1983. 12:625-29.

Rogers C. E. Extrafloral nectar: Entomological implications. Bull. Entomol. Soc. Amer. 1985. 31(3):15-20.

Root R. B. Organization of a plant-arthropod association in simple and diverse habitats: The fauna of collards (Brassica oleracea). Ecol. Monogr. 1973. 43:94-124. DOI: 10.2307/1942161 [CrossRef]

Ryan J., Ryan M. F., McNaeidhe F. The effect of interrow plant cover on populations of the cabbage root fly, Delia brassicae (Wiedemann). J. Appl. Ecol. 1980. 17:31-40. DOI: 10.2307/2402961 [CrossRef]

Salas-Aguilar J. Studies on Orius tristicolor (White) in northern California 1976. p.31. M.S. thesis. Davis: Univ. Calif

Salas-Aguilar J., Ehler L. E. Feeding habits of Orius tristicolor. Ann. Entomol. Soc. Amer. 1977. 70:60-02.

Shahjahan M. Effect of diet on the longevity and fecundity of the adults of the tachinid parasite Trichopoda pennipes pilipes. J. Econ. Entomol. 1968. 61:1102-3.

Sheehan W. Response by specialist and generalist natural enemies to agroecosystem diversification: A selective review. Environ. Entomol. 1986. 15:456-61.

Sims W. L., Smith P. G. Growing peppers in California. 1976. Oakland: Univ. Calif. Div. Agric. Nat. Resour. 12p. Leaflet 2676

Smith J. G. Some effects of crop background on populations of aphids and their natural enemies on brussels sprouts. Ann. Appl. Biol. 1969. 63:326-30. DOI: 10.1111/j.1744-7348.1969.tb05497.x [CrossRef]

Summers C. G., Garrett R. E., Zalom F. G. A new suction device for sampling arthropod populations. J. Econ. Entomol. 1984. 77:817-23.

Summers C. G., Gilchrist D. G., Norris R. F. Integrated Pest Management for Alfalfa Hay. 1981. Oakland: Univ. Calif. Div. Agric. Nat. Resour. Publ. 3312p.

Sundby R. A. Influence of food on the fecundity of Chrysopa carnea Stephens (Neuroptera: Chrysopidae). Entomophaga. 1967. 12:475-79. DOI: 10.1007/BF02376933 [CrossRef]

Syme P. D. The effects of flowers on the longevity and fecundity of two native parasites of the European pine shoot moth in Ontario. Environ. Entomol. 1975. 4:337-46.

Syme P. D. Observations on the longevity and fecundity of Orgilus obscurator (Hymenoptera: Braconidae) and the effects of certain foods on longevity. Can. Entomol. 1977. 109:995-1000. DOI: 10.4039/Ent109995-7 [CrossRef]

Tamaki G., Lashomb J. H., Casagrande R. Biological control of potato pests. Advances In Potato Pest Management. 1981. Stroudsburg, Penn.: Hutchinson Ross. p. 178-92.

Tamaki G., Weeks R. E. Biology and ecology of two predators, Geocoris pallens Stal and G. bullatus (Say). USDA Tech. Bull. 1972. 1446:46

Tamaki G., Weiss M. A., Long G. E. Evaluation of plant density and temperature in predator-prey interactions in field cages. Environ. Entomol. 1981. 10:716-20.

Thead L. G., Pitre H. N., Kellogg T. F. Feeding behavior of adult Geocoris punctipes (Say) (Hemiptera: Lygaeidae) on nectaried and nectariless cotton. Environ. Entomol. 1985. 14:134-37.

Topham M., Beardsley J. W. Jr. Influence of nectar source plants on the New Guinea sugarcane weevil parasite, Lixophaga sphenophori (Villenueve). Proc. Haw. Entomol. Soc. 1975. 21:145-57.

Treacy M. F., Benedict J. H., Walmsley M. H., Lopez J. D., Morrison R. K. Parasitism of bollworm (Lepidoptera: Noctuidae) eggs on nectaried and nectariless cotton. Environ. Entomol. 1987. 16:420-23.

U.S. Department of Agriculture. Selected Weeds of the United States. Agricultural Research Service, U.S. Department of Agriculture, Agricultural Handbook No. 1970. 366:463

van Emden H. F. Observations on the effect of flowers on the activity of parasitic Hymenoptera. Entomologist’s Mon. Mag. 1962. 98:265-70.

van Emden H. F. The effect of uncultivated land on the distribution of cabbage aphid (Brevicoryne brassicae) on an adjacent crop. J. Appl. Ecol. 1965. 2:171-96. DOI: 10.2307/2401703 [CrossRef]

William R. D. Complementary interactions between weeds, weed control practices, and pests in horticultural cropping systems. HortScience. 1981. 16:10-15.

Wilson L. T., Gutierrez A. P. Within-plant distribution of predators on cotton: Comments on sampling and predator efficiencies. Hilgardia. 1980. 48:3-12. DOI: 10.3733/hilg.v48n03p018 [CrossRef]

Winer B. J. Statistical Principles in Experimental Design (second ed.). 1971. New York: McGraw-Hill. 907p.

Yokoyama V. Y. Relation of seasonal changes in extrafloral nectar and foliar protein and arthropod populations in cotton. Environ. Entomol. 1978. 7:799-802.

Bugg R, Ehler L, Wilson L. 1987. Effect of common knotweed (Polygonum aviculare) on abundance and efficiency of insect predators of crop pests. Hilgardia 55(7):1-52. DOI:10.3733/hilg.v55n07p052
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