Biological Control and Its Integration in Weed Management Systems for Purple and Yellow Nutsedge (Cypems rotundus and C. esculentus)' SHARAD C. PHATAK, M. BRETT CALLAWAY, and CHARLES S. VAVRINA' amples of successful control and several examples Observations of the effects of living organisms on of failure. weeds dates from 1795 when an insect, Dactylopius A total of 132 insects have been associated with ceylonicus, was introduced for drooping pricklypear purple (Cypems rotundus L. #3 CYPRO) and/or (Opuntia vulgaris Miller) control over a vast area yellow nutsedge (Cypems esculentus L. # CYPES) (42, 60, 93, 112). Since that time, biological control (Table 1). Approximately half of these insects are of weeds employed mainly the classical strategy known to feed on crop plants. Four insects on of introducing natural enemies from areas of co- nutsedges have been studied in detail. Three moths, evolution. Self-perpetuation and dissemination of Bactra verutana Zeller in the United States, B. these introduced enemies was essential to suppress minima Meyrick and B. venosana Zeller in the successfully the weed below economic levels (6, Indian subcontinent, and one weevil, Athesapeuta 8). This classical tactic is suited particularly for cypen' Marshall in southeast Asia (34). All are ade- weeds that are distributed widely in less intensively quately host-plant specific, but none have proved cropped or noncropped areas (6, 41). Guidelines effective as classical biological control agents. For to introduce foreign organisms for biological control example, A. cyperi was introduced to control purple of weeds in the United States have been established nutsedge in Barbados in 1973, Cook Islands in (63). 1971 and 1973, and Fiji and Tonga in 1971 but The strategy of augmenting an indigenous natural has not been recovered. It did become established enemy to kill or to suppress the weed host by apply- in Hawaii following releases in 1925 but had ing high inoculum pressure at an appropriate time negligible effect on purple nutsedge. B. minima has been termed bioherbicide tactic (108, 109) was released in the Cook Islands in 1973 and Fiji or inundative biological control (119). This strategy and Tonga in 1971 but also was not recovered. also is referred to as a biological herbicide, a micro- B. venosana was released with similar results in bial pesticide, or a mycoherbicide; the latter term Barbados in 1973 and Cook Islands in 1971. It refers to fungal pathogens only. It is best suited was established in Fiji from releases in 1936 and for weed control in annual crops where rapid con- 1971 but was subject to high parasitism. Thus, trol or suppression of the weed is generally attempts to control purple nutsedge with classical desired. biological control have failed with the four insects tested at several locations. CLASSICAL BIOLOGICAL CONTROL WlTH INSECTS Julien (60) listed the introduction of 225 orga- INUNDATIVE BIOLOGICAL CONTROL WlTH INSECTS nisms against 111 weed species, including 178 insects and 6 mites. The catalogue has many ex- In Mississippi, as a result of having a continuous supply of B. verutana available (40), the effects of augmentation in a series of greenhouse (37, 38) and field tests under cages (35) were studied. In preliminary tests, the introduction of freshly ' Received for publication July 23, 1985. 2Prof. and Grad. Students, respectively, Dep. Hort., Coastal Plain emerged adult moths into cages did not produce Exp. Stn., Univ. Georgia, Tifton, GA 31793. Current address of consistent infestations. In the field, the percent- M. Brett Callaway, Dep. Veg. Crops, Cornell Univ., Ithaca, NY 14840, and Charles S. Vavrina, Ext. Serv., Univ. Georgia, Statesboro, ages of infestation were proportional to the num- GA 30458. bers of adults used, i.e., field cages (2 by 2 by 2 m 'Letters following this symbol are a WSSA-approved computer code from Composite List of Weeds, Weed Sci. 32, Suppl. 2. Avail- or 2 by 4 by 2 m) receiving 2, 10, and 60 pairs able from WSSA, 309 West Clark Street, Champaign, IL 61820. of adults had 0, 33, and 100% of the purple nut- 84 Weed Technology. 1987. Volume 144-91 WEED TECHNOLOGY Table 1. Insects of Cyperus rotundus and/or Cyperus esculentus. Organism Common name Species infected References Aleurocybotus sp., whitefly Cyperus rotundus A. occiduus sp.n. C. rotundus and C. esculentus Althaeus hibisci (Oliver) C. esculentus Amsacta moorei (Btlr.) C. rotundus Anacentrinus blanditus (Casey) C. rotundus Anthomyza sp. C. esculentus Antonina australis (Green) [syn. of Kuwanina hill;, (Laing)] C. rotundus Apis indica C. rotundus Athesapeuta cyperi (Mshl.) C. rotundus and C. esculentus Bactra bactrana (Kennel) C. rotundus B. furfurana (Haworth) C. rotundus and C. esculentus B. lanceolana (Hubner) C. rotundus and C. esculentus B. minima minima (Meyrick) C. rotundus B. pbaeopis (Meyr.) C. rotundus and C. esculentus B. truculenta [syn. of venosana (Meyr.)] C. rotundus and C. esculentus B. venosana (Zeller) C. rotundus B. verutana (Zeller) C. rotundus and C. esculentus Bagrada cruciferarum C. rotundus Barinus squamolineatus (Casey) C. esculentus B. curticollis (Casey) C. esculentus Barilepis grisea (Leconte) C. esculentus Calendra sp. C. esculentus Calligypona striatella (Fall.) C. rotundus Carolinaia cyperi (Ainslie) aphid C. esculentus Chaetocnema denticulata (Ill.) C. esculentus Cbaeocnema pulicaria (Melsheimer) C. rotundus Chaetopsis fulvifrons (Macquart) C. esculentus Chiloides copidotis (Meyrick) C. rotundus Cblorops sp. C. esculentus Cborizococcus rostellum (Hoke) mealybug C. rotundus and C. esculentus Cisseps fulvicollis (Hubner) C. rotundus Corimelaena pulicaria (German) C. esculentus Culex pipiens quinque sp. fasciatus C. rotundus Cydia perfricta (Meyr.) C. rotundus Delphacodes puella (Van Duzee) C. rotundus Delphacodes basivitta (Van Duzee) C. esculentus Deltocephalus sonorus (Ball) C. rotundus Diabrotica undecempuncta ta howardi (Barber) C. esculentus Dorcadotbrips coespitis (Priesner.) C. rotundus Draculacephala portola (Ball) C. rotundus Elachiptera nip'ceps (Loew.) C. esculentus Elasmopalpus lignosellus (Zeller) C. rotundus Elliponeura debilis (Loew.) C. esculentus Euscyrtus concinnus C. rotundus Evylaeus sp. C. rotundus Exitianus exitiosus (Uhler) C. rotundus Fervisia virgata (Cockrell) C. rotundus Frankliniella fusca (Hinds) C. rotundus Gastrimargus transversus (Thnb.) C. rotundus Glypbipterix impigritella (Clemens) C. rotundus and C. esculentus Glyphipteryx prob. impigritella C. esculentus Graminella nipyrons (Forbes) C. rotundus Halticus bracteatus (Say) C. esculentus Halictus lucidipennis C. rotundus Haplaxius crudus (Van D.) C. esculentus Heliothis virescens Tobacco budworm C. rotundus Laodelphax striatella (Fallen) C. rotundus Lasiglossum albescens C. rotundus Laspeyresia perfricta (Meyrick) C. rotundus Lerema accius (Smith) C. rotundus Liburniella ornata (Stal) C. esculentus Lissorboptrus brevirostris (Suffr.) C. esculentus Locusta migratoria capito (Sauss.) C. esculentus Macrosiphum avenue C. esculentus Macrosteles fascifrons (Stal) C. rotundus Marasmia trapezalis (Gn.) C. rotundus 12 (continued) Volume 1, Issue 1 (January), 1987 WEED TECHNOLOGY sedge infested, respectively. In the greenhouse, gens dates from 1893 and 1894 in New Jersey when two pairs of adults introduced into small cages experiment station bulletins reported a list of fungi in two series of tests produced infestations in 60 injurious to weed seedlings (44, 45). At the same and 66% of the cages. The erratic results probably time, a grower wrote in a letter to the New Jersey reflect a lack of food and moisture that killed or Experiment Station, "Two years ago about an acre weakened the females during their 2-day preovi- of a farm was over run by Canada thistle [Cirsium position period (40). arvense (L.) Scop. # CIRAR], but by the time The use of first-instar larvae generally gave con- they were in full bloom a rust struck and hardly sistent results. In the greenhouse, an infestation any of them matured. We plowed the land in the of shoots with a single application of 2 or 5 larvae fall and last year scarcely a thistle appeared. If per shoot (37) or with 3 larvae per shoot (38) caused this rust could be disseminated through the country, significant damage to purple nutsedge. Weekly the Canada thistle would receive a substantial check" introductions were more damaging than a single (121). In his review on using plant pathogens in one: single introductions averaged 5 5% reduction weed control, Wilson (121) said, "To write a con- in shoot dry weight; 2, 3, or 4 introductions re- clusion for this subject in its present state of growth sulted in average reduction of 77%; and eight intro- seems premature. So let us consider where we might ductions reduced top growth 98% (38). The number go from here." and weight of tubers were reduced 86 and 88%, Books edited by Charudattan and Walker (23) respectively, in the greenhouse (37) but were only and Kurstak (64) access the substantial progress 26 and 38%, respectively, in the field. Early re- made since the initial reports. Templeton (107) lease of larvae increased damage in the field but reported 42 active projects, while Scheepens and not as much as in the greenhouse. van Zon (100) listed 43 projects using plant patho- According to Frick (34), wherever purple nut- gens to control weeds. One project not cited involves sedge is a problem, biological control with insects use of the fungus, Puccinia canaliculata (Schw.) probably will involve manipulating the local or Lagerh., for yellow nutsedge