CARIBBEAN FOOD CORPS SOCIETY

SERVING THE CARIBBEAN SINCE 1963 CARIBBEAN FOOD CROPS SOCIETY 39 Thirty Ninth Annual Meeting 2003

Grenada Vol. XXXIX Number 1 Proceedings of the Caribbean Food Crops Society. 39(2):200-146. 2003

DRAMATIC IMPACT OF THE RECENTLY INTRODUCED ASIAN PIGEON PEA POD FLY, MELANAGROMYZA Ο Ml SA (MALLOCH) (DIPTERA: AGROMYZIDAE), IN THE

Colmar A. Serra_, Socorro Garcla_, Yony Segura_, and Juan AriasInstituto Dominicano de Investigaciones Agropecuarias y Forestales (IDIAF), JPrograma Nacional de Protecciôn Vegetal, Santo Domingo, Dominican Republic.

ABSTRACT: The pigeon pea (Cajanus cajan (L.) Millsp.) is the second most important leguminous crop for the Dominicans. Fresh or canned seeds are also exported, i.e., to Puerto Rico and the U.S.A. The crop with very low input requirements is produced in marginal areas and serves as an important source of protein for the peasant farmers. The pigeon pea pod fly (.Melanagromyza ob tus a Malloch) has been a pest in Asian countries for decades and was first reported in the western hemisphere in Puerto Rico and the Dominican Republic in the year 2000 (NPAG 2000; Kauffman 2001; Abud et al., 2002). Alerted by local farmers, between 2002 and 2003 two separate research teams, based at and San Francisco de Macoris, carried out a survey. The study consisted in the determination of the dispersal of the recently introduced pest, the damage levels and the presence and effectiveness of antagonists of the pest. Pods were collected from plants in more than 20 localities belonging to 5 provinces of the major pigeon pea producing regions in the southwest and south, as well as of more than 20 localities of 8 provinces in the central and north-eastern regions, being present at >95% of the surveyed sites. The infested pods showing small "windows" ranged between 30 to 80% and the damaged seeds between 10 and 80%. From the pods held in paper bags conected to glass tubes, no single parasitoid emerged. The mass release of introduced parasitoids is discussed, trying to reduce the damage by at least 50% and backing biocontrol applying 1PM measures.

INTRODUCTION

The pigeon pea pod fly (PPF), Melanagromyza obtus a (Malloch) (Diptera: Agromyzidae), originates from Asia, where it has been reported for decades as an important pest of C. cajan, in India, Sri Lanka, the Philippines, Thailand, Indonesia, Japan, and Vietnam (Spencer, 1973). The host-plant range includes leguminous genera as Cajanus, Flemingia, Rhynchosia, and others. One interception of M. obtusa on soybean has alerted the authorities of the U.S.A., but has to be confirmed as a host as well as okra (Abelmoschus esculentus, Malvaceae), Sesamum indica L. (Pedaliaceae), and Vigna spp. (Leguminosae-Papilionoideae). The first interceptions in the Western Hemisphere were reported in 2000 from Puerto Rico and the Dominican Republic (NPAG, 2000; Abreu et al., 2000; Abud and Cuevas, 2002) and in 2003 identified in Cuba by Serra (unpubl. data).

BIOLOGY

The life cycle takes between 4 to 5 weeks (Table 1). The PPF female stings into developing pigeon pea pods and lays up to 80 eggs individually. Normally, more than one egg and up to 7 eggs are found in a single pod, 4 being the average (Spencer 1973). After hatching

143 inside the pod the larvae start feeding on the surface of the seeds before boring into the seed. The larvae complete their development, consisting of 3 instars, well protected and practically undetectable until they leave the seed before pupation to feed on the wall of the pod leaving a characteristic oval or round "window" (φ 1-2.5 mm) with an epidermal layer, which is perforated by the emerged adult to leave the pod. The adult is a medium sized dark to green metallic fly.

Table 1. Developmental data of the pigeon pea pod fly (Shanover et al., 1999; NPAG, 2000)

Stages Duration (development eggs>adults: 18-39 days) Eggs 3-5 days Larvae, 3 instars 6-11 d LI-1.5 d; L2 -~~2 d; L3 2.5 d Pupae (l.~3 mm) 9-23 d (inside the pod) Adults (length~2-2.5mm) ~12 days (longevity)

MATERIALS AND METHODS

The main objective of this study was to confirm the presence of the PPF, their associated natural enemies and the damage levels in the different regions where Cajanus cajan is grown commercially or extensively planted along the roads. The studies were carried out between January 2002 and May 2003 by two teams of the Plant Protection Program of the IDIAF, based at the Estaciôn Experimental Arroyo Loro (EEAL), province San Juan de la Maguana in the southwest, and the Estaciôn Experimental Mata Larga (EEML), San Francisco de Macoris in the northeastern province Duarte. The team of the EEAL evaluated fields in 19 localities in the southern and southwestern provinces of Elias Piria (3), San Juan de la Maguana (12), Barahona (1), Ocoa (2), and San Cristobal (2). The team of the EEML evaluated pigeon pea pods sampled in 24 localities belonging to 8 provinces between the southwest and northeast of the country. Ripe pods were collected at random and put in paper bags (20 cm χ 10 cm) and brought to the laboratories, where the aperture was connected with a glass tube (12-15 cm long) held up side down by rubber tie to permit the detection of emerging flies and parasitoids flying towards the light. In the studies carried out by the EEML team, the pupae, emerging flies, percentage attacked pods, and seeds were recorded.

RESULTS

The PPF was found in every locality where samples of pigeon pea pods were taken, with one exception. In the Dominican Republic, a narrow alternative host plant range has been confirmed up to date: Rhynchosia minima, Rhynchosia reticulata, and Flemingia macrophylla (all Leguminosae-Papilionoideae) (Table 2). Only in one pigeon pea sample out of more than 3,000 checked, a parasitizised pupal case was detected, but the parasitoid was not found. Only at 2 dates and in a few of the tiny pods of Rhynchosia minima collected in fields of the EEAL, still no confirmed parasitoids (Euderusl sp., Hymenoptera: Eulophidae) emerged. No specific predators nor fungal or other diseases of the PPF as biocontrol agents have been found up to date.

201 Table 2. Host plants of Melanagromyza obtusa confirmed in the Dominican Republic.

Host plant Date Localities Collectors Parasitoids Cajanus cajan (L.) Millsp. See Tables 3 and 4 0 Flemingia macrophylla 29/9/03 , C.A. Serra 0 (Willd.) Kuntze ex Merr. Samanâ Rhynchosia minima (L.) 14/7/02, EEAL, San Juan Y. Segura, J. Arias 8,1 DC. 3/4/03 de la Maguana & C.A. Serra Rhynchosia reticulata 15/6/03 Oviedo M. Reyes (pers. not evaluated (Sw.) DC. comm.)

The results of the samples achieved by the EEAL team concerning the damage caused by the PPF can be seen in Table 3. The percentages of damaged pods varied between 10 and 65%. The lowest infestation levels were recorded in samples coming from altitudes above 400 m.a.s.l. and in localities with a relatively high use of pesticides (San Cristobal).

Table 3. Infestation levels of pigeon pea (Cajanus cajan) pods by Melanagromyza obtusa in 19 localities of the south and southwest region of the Dominican Republic. Province Locality Infested pods (%) Elias Pina Guanito, El Llano 62 El Reboso, El Llano 65 La Fuente, 45 San Juan de la Maguana Buena Vista 30 Ginova 32 La Culata 61 Aromar 65 Km7, Road San Juan M.-Las Matas 35 Hato del Padre 60 Chalona 41 El Corbano 25 Las Matas de Farfân 35 , Aguas Frescas 10 Los Arroyos 24 Barahona La Sabana Polo 10 San José de Ocoa Ojo de Agua 25 Arroyo Hondo 20 San Cristobal Palenque 15 Dona Ana 12

The results obtained by the EEML team are presented in Table 3. The infestation levels of the PPF varied between 3 and 100% of the pods, while between 20 and 85% of the seeds of infested pods were found damaged. The percentage of damaged seeds referred to the total amount of sampled pods ranges between 2 and over 80%. The lowest levels were obtained in mountain valleys as in or near Constanza at higher altitudes (800-1,200 m.a.s.l.) and beginning

202 the harvesting season (Table 4). In some places, the levels at the end of the harvesting season reached levels above 50% of the total seeds. Figures 1 and 2 show the damaged caused by the PPF on green and dry pods of pigeon pea. Figure 3 shows the pupal cases and emerged adults of the pigeon pea pod fly, recovered from the pods. There was no presence of parasitoids.

Larva L3

Figure 1. Non-infested (left) and attacked (right) green pods of pigeon pea showing seeds damaged by the pigeon pea pod fly (PPF), Melanagroniyza öbtusa (Malloch) (Diptera: Agromyzidae).

203 '

micelia

Figure 2. Infested dry pods of pigeon pea showing seeds damaged by the pigeon pea pod fly (PPF) and covered with micelia of fungi after secondary infection.

204 Table 4. Infestation levels of green pigeon pea pods and damaged seeds by Melanagromyza obtusa in 24 localities between the National District, the center and northeast of the Dominican Republic.

Province Locality Month % infested % damaged seeds of pods infest, pods total pods National District Santo Domingo Jul.'02 52 72 37 Santo Domingo Feb.'02 23 36 8 Monsenor Nouel Juma, Nov.'02 63 47 30 Juma, Bonao Dec.'02 65 49 32 Sanchez Ramirez Angelina, Cotui Oct.O2 32 64 21 La Vega Bacumi, May'03 53 47 25 Arroyo Frio Jul.'02 100 82 82 Constanza Jul.'02 9 42 4 Constanza Jul.'02 34 52 18 Constanza Aug.'02 44 64 28 Constanza Oct.'02 47 65 31 Constanza Dec.'02 33 38 13 Constanza Jan.'03 19 28 5 La Cienaga Dec.'02 10 20 2 El Rio Dec.'02 15 33 5 El Rio Dec.O2 27 33 9 Jima Apr.'02 79 39 30 Jima May'02 59 33 20 Ranchito Apr.'02 28 23 7 Ranchito Apr.'02 53 81 43 Ranchito Dec.'02 75 69 51 Ranchito Jan.'03 19 32 6 Ranchito Feb.'03 70 54 38 Duarte La Penda, S FM. Nov.'02 95 64 61 El Jamo, SFM. Feb.'02 78 55 43 Salcedo Salcedo Nov.'02 59 52 31 Jayabo Jan.'03 50 46 23 Monte llano Jan.'03 63 42 27 Maria Trinidad , Jan.'03 87 58 50 Sanchez El Pozo, Nagua Mar.'03 64 37 24 Canela, El Pozo Apr.'03 81 37 30 Samanâ Juana Vicente Jul.'02 70 72 50 Las Terr en as Apr.'02 100 81 81 Las Terrenas Aug.'02 30 85 26 Las Terrenas Jan.'03 40 23 9 Las Terrenas (d) Feb.'03 43 35 15 EI Naranjito, LT. Mar.'03 44 43 19 J ul.'02 70 66 46 Sanchez Jan.'03 27 25 7

205 Figure 3. Pupal cases and emerged adults of the pigeon pea pod fly (PPF), recovered from the pods, without presence of parasitoids.

CONCLUSIONS AND RECOMMENDATIONS

The studies carried out in 13 provinces located in the south, southwest, and northeast regions of the Dominican Republic showed that the pigeon pea pod fly is a serious threat to pigeon pea, an economically important crop in the Dominican agriculture, for national markets, export and as a source of protein and income, specially for the poor rural segments of the population. The latter, usually do not use any phytosanitary measures in this crop with low input requirements. It was also found that the immature stages complete their cycle well protected inside the pods. As alternative host plants were confirmed Rhynchosia minima, Rhynchosia reticulata, and Flemingia macrophylla (all Leguminosae-Papilionoideae). Only from Rhynchosia minima pods emerged a few parasitoids of the PPF. Also in Puerto Rico, PPF parasitoids were recovered from Rhynchosia spp., but not from pigeon peas (Abreu, pers. comm.). The absence of effective biocontrol agents in pigeon pea itself, makes necessary the implementation of a classical biological control program based on the most promissing parasitoids screened and selected after a foreign exploration in Asia, where the pest originated. An environmental assessment has been achieved in order to permit the introduction of exotic parasitoids of the PPF to Puerto Rico, after a selection of the most promising species and the exclusion of hyperparasitoids. The existence of effective parasitoids has been reported from different Asian countries (Meyerdirk, 2003, not publ.). An IPM approach should include the search for tolerant cultivars as well as selective insecticides and measures in order to support biocontrol.

206 REFERENCIAS

Abreu, Ε., Α. Armstrong, Α. Bosques, Ε. Acevedo y V. Gonzalez. 2000. La Mosca Asiâtica de la Vaina del Gandul (Melanagromyza obtusa, Malloch), Una Nueva Plaga del Gandul en el Neotrôpico. Univ. of Puerto Rico, Recinto de Mayagüez. Abud, A. y R. Cuevas. 2002. Nueva plaga minadora en el guandul. Agroempresa (Dominican Republic)14(2):20. Meyerdirk, D.E. (2003, unpubl.). Control of pigeon pea pod fly, Melanagromyza obtusa (Diptera: Agromyzidae). Environmental assessment. Draft, April 14, 2003, 32 pp. Godoy, G., E. Arnaud y J. Arias. 1997. La Cancerosis del Tallo del Guandul. Proyecto Cooperativo Titulo XII, Hoja Divulgativa, 4-97, San Juan de la Maguana, D.R. Kauffman, B. 2001. Potential new Project with the Dominican Republic offshore initiative: Melanagromyza obtusa, the pigeon pea pod Fly. USDA, APHIS, PPQ, Western Regional Office. Ft. Collins, Colorado: 1 pp. NPAG, 2000. NPAG DATA: Melanagromyza obtusa, Pigeon pea Pod Fly, potential threat to pigeon pea in Puerto Rico, March 15, 2000. USDA, APHIS, NPAG Reports: 1-11. Schmutterer, H. 1990. Crop pests in the Caribbean- Plagas de las plantas cultivadas en el Caribe. Deutsche Gesellschaft fuer technische Zusammenarbeit (GTZ) GmbH, Eschborn, Germany. Shanover, T.G., J. Romeis, and E.M. Minja. 1999. Insect pests of pigeon pea (Cajanus cajan) and their management. Annual Review of Entomology. 44:77-96. Segura, Y., G. Godoy de Lutz y J. Arias. 2003. Diagnôsticos de plagas y enfermedades en el cultivo del guandul (Cajanus cajan (L.) Millsp.) en parcelas de productores en zonas bajas y montanosas de la Region Suroeste. Instituto Dominicano de Investigaciones Agropecuarias y Forestales (IDIAF), CENIAF, San Juan de la Maguana, Dominican Republic. Spencer, K.A. 1973. Agromyzidae (Diptera) of economic importance. Series entomolôgica. Dr. W. Junk, The Hague, Netherlands, 45: 1-444.

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