Intercropping Cabbage and Indian Mustard for Potential Control of Lepidopterous and Other Insects
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HORTSCIENCE 34(2):275–279. 1999. with no insecticide, and the third required only two applications. Later studies indicated that paired mustard rows at either end of 25 cab- Intercropping Cabbage and Indian bage rows was the most effective planting pattern for successful DBM management Mustard for Potential Control of (Srinivasan and Krishna Moorthy, 1992). Insects can attack cabbage soon after emer- Lepidopterous and Other Insects gence, making it necessary to seed the mustard 15 d before seeding the cabbage to ensure David A. Bender adequate trap crop foliage. Indian mustard also completes vegetative growth and flowers Texas A&M Agricultural Research and Extension Center, Rt. 3, Box 219, ≈40 d after seeding, after which it becomes Lubbock, TX 79401-9757 less attractive to DBM. Succession plantings of Indian mustard in paired rows were neces- William P. Morrison and Raymond E. Frisbie sary to maintain an effective trap crop Department of Entomology, Texas A&M University, College Station, (Srinivasan and Krishna Moorthy, 1991). TX 77843-2475 Luther et al. (1996) evaluated a similar intercropping system in Hawaii. In their stud- Additional index words. Brassica oleracea, Brassica juncea, diamondback moth, cabbage ies, numbers of DBM larvae in cabbage inter- looper, harlequin bug, integrated pest management cropped with Indian mustard were equal to or greater than those in cabbage planted alone. Abstract. A system of intercropping cabbage (Brassica oleracea var. capitata L.) with Other lepidopterous pests were preferentially Indian mustard [Brassica juncea (L.) Czern.] to reduce pesticide applications was evalu- attracted to Indian mustard or a highly suscep- ated over three cropping seasons. Insects were monitored in nonintercropped cabbage, tible cabbage cultivar used as trap crops. The cabbage plots surrounded by Indian mustard, and the Indian mustard intercrop. Insecti- potential for using a similar intercropping sys- cide applications were made to individual plots based on specific treatment thresholds for tem for controlling lepidopterous crucifer pests lepidopterous insects and accepted pest management practices for other insects. Inter- in other areas has not been determined. In cropping had no significant effect on the number of lepidopterous larvae in cabbage. 1992 a study was initiated to evaluate a cab- Indian mustard did not appear to preferentially attract lepidopterous insects, but was bage–Indian mustard intercrop system under highly attractive to hemipterans, especially harlequin bugs [Murgantia histrionica (Hahn)]. Texas High Plains growing conditions. In one season with heavy harlequin bug pressure, intercropping with Indian mustard eliminated two insecticide applications to cabbage. Intercropping cabbage with Indian mustard does not appear to be an economical pest management practice under normal pest Methods and Materials pressures in West Texas. Culture. Trap crop research plots were established in late Spring and Fall 1992 and Diamondback moth [Plutella xylostella of success (Buranday and Raros, 1975; Latheef late Spring 1993 on an Acuff loam (fine- (L.)] (DBM) is a major insect pest of cabbage and Irwin, 1979; Latheef and Ortiz, 1983). loamy, mixed-thermic, Aridic Paleustoll) at and other crucifers worldwide. Resistance of Buranday and Raros (1975) reported that in- the Texas A&M Agricultural Research and DBM to all major classes of insecticides terplanting cabbage and tomatoes (Lycopersi- Extension Center, Lubbock, Texas (Table 1). (Cheng, 1986; Myata et al., 1986; Shelton and con esculentum Mill.) reduced DBM damage Irrigation based on tensiometer readings of Wyman, 1992; Sun et al., 1986) and to some to cabbage. Talekar et al. (1986) intercropped >25 kPa was applied through a drip system. biologicals (Tabashnik et al., 1990) has been cabbage in Taiwan with 54 different crops for Preplant fertilization with N (90 kg·ha–1) and P reported, making DBMs an increasingly sig- control of DBM. Tomato, dill (Anethium (112 kg·ha–1) was supplemented by two nificant component of the crucifer pest com- graveolens L.), safflower (Carthamus sidedress applications of N (20 kg·ha–1) through plex. Since the mid-1980s DBM has emerged tinctorius L.), garlic (Allium sativum L.), oat the irrigation system. as a major threat to cabbage production in the (Avena sativa L.), and barley (Hordeum vulgare Oilseed-type Indian mustard seed was ob- southwestern United States (Magaro and L.) reduced DBM damage to cabbage. Mus- tained from Dr. K. Srinivasan, Indian Institute Edelson, 1990), at times causing loss of entire tard was included in the study, but was not one of Horticultural Research, Bangalore, India, fields. An integrated program combining ag- of the species reported to be effective for and increased in 1991 by Dr. Robert Cartwright, gressive sanitation practices, alternation of intercropping. Oklahoma State Univ. Mustard was seeded at classes of insecticides, and inclusion of Bacil- Srinivasan and Krishna Moorthy (1991) 3–5 cm spacing in one of two border rows of lus thuringiensis (Bt) materials in every insec- reported that Indian mustard was favored over each protected plot and the end border area of ticide application has provided economically cabbage as an oviposition host for DBM. Cab- two of the three cabbage rows (Fig. 1) 15–25 acceptable control (Talekar and Shelton, 1993). bage grown alone in field tests at Bangalore, d before seeding of cabbage in the spring and However, the long-term success of this ap- India, had significantly higher larval popula- 8 d before seeding in midsummer (Table 1). proach is uncertain, and alternative control tions than did cabbage intercropped with In- When Indian mustard from the first seeding strategies that reduce pesticide use are needed. dian mustard. Mustard rows were seeded be- bolted, the second seeding was made in the Interplanting cruciferous crops with vari- tween each 15 rows of cabbage and sprayed at remaining border areas. Plants from the first ous companion species to reduce lepidopter- 10-d intervals to control insects. In three tests, seeding were removed before seed pods dried ous pest pressure has met with varying levels two cabbage crops were successfully grown sufficiently to begin shattering. A third seed- Received for publication 3 Feb. 1998. Accepted for Table 1. Planting and harvest dates for interplanting studies with cabbage and mustard. publication 13 July 1998. This research was par- tially funded by ES-USDA Grant 91-EPMP-1-0005. Seeding dates We thank Ed Riley, Dept. of Entomology, Texas Mustard A&M Univ., for the identification of insects in this Crop First Second Third Cabbage Harvest dates study, and Don Douglas and John Baker for techni- Spring 1992 22 Apr. 8 June 8 May 11 Aug. cal assistance. The cost of publishing this paper was 25 Aug. defrayed in part by the payment of page charges. Fall 1992 28 July 4 Sept. 5 Aug. 28 Nov. Under postal regulations, this paper therefore must Spring 1993 27 Apr. 2 June 17 June 20 May 3 Sept. be hereby marked advertisement solely to indicate 16 Sept. this fact. HORTSCIENCE, VOL. 34(2), APRIL 1999 275 PEST MANAGEMENT ing was made in 1993, when mustard plants with higher toxicity or longer residual were curred in mid-July, coinciding with the ap- from the first seeding were removed to ensure used only when the aforementioned treatments pearance of second-generation harlequin bugs. that protected plots were surrounded by non- failed to maintain insect numbers below ac- These insects were also highly attracted to flowering Indian mustard throughout the cab- ceptable levels. In several cases, protection of Indian mustard, and were so numerous as to bage growing season. the Indian mustard with insecticide applica- threaten survival of the intercrop. The last Experimental design. Plots were arranged tions was necessary even when the cabbage carbaryl application for control of harlequin in a randomized complete-block design with was not infested. bugs also controlled the false chinch bugs, and four replications. Intercropped cabbage plots no further economic infestations of these two (IN) 9.2 m × 3.1 m in size, comprised of three Results pests occurred. single rows of ‘Bravo’ cabbage spaced 0.3 m The lepidopterous insect complex was com- within rows and 1.0 m between rows, were Spring 1992. Three early-season carbaryl posed primarily of DBM and cabbage loopers bordered by two rows of Indian mustard on the [1-napthalenyl methylcarbamate] applications [Trichoplusia ni (Hubner)], although a few sides and by 1.8 m at the end of plots. were required to control western black flea southern cabbageworms [Pontia protodice Nonintercropped cabbage plots (NIN) were beetles (Phyllotreta pusilla Horn) on emerg- (Boisduval and LeConte)] and imported cab- planted in the same configuration but physi- ing Indian mustard seedlings, with cabbage bageworms [Pieris rapae (L.)] were present cally isolated from Indian mustard by a mini- transplants requiring two applications (Table (Fig. 3). Larvae of DBM appeared in both IN mum of 10 m. 2). In early June, a few harlequin bugs were and NIN cabbage in early June and numbers Insect monitoring. Counts of all insects observed on the Indian mustard (Fig. 2). Over increased rapidly in mid-June. Cabbage loop- found on five center-row cabbage and five one weekend (5–8 June), immigration in- ers appeared about the same time, but did not Indian mustard plants in each plot were made creased adult harlequin bug numbers to 24 per reach economic levels until early July. An at 3- to 7-d intervals depending on insect plant in the Indian mustard. Three carbaryl initial Bt (Javelin, Sandoz Crop Protection pressure. Lepidopterous larvae were classi- applications were needed to control the adults Corp., Des Plaines, Ill.) application on 23 June fied as small, medium, or large, and eggs, and the nymphs that emerged from egg masses reduced lepidopterous larvae numbers below pupae, and adults were counted where practi- deposited on the plants. A subsequent genera- the treatment threshold, but populations quickly cal. Numbers of beneficial insects were also tion in mid-July necessitated two additional recovered as cabbage looper numbers in- recorded.