CONTROL OF COCOA POD BORER AND PHYTOPHTHORA POD ROT USING DEGRADABLE PLASTIC POD SLEEVES AND A NEMATODE, Steinernema carpocapsae

41 Control of cocoa Indonesian Journal pod of borer Agricultural and Phytophthora Science pod 11(2), rot ... 2010: 41-47 CONTROL OF COCOA POD BORER AND PHYTOPHTHORA POD ROT USING DEGRADABLE PLASTIC POD SLEEVES AND A NEMATODE, Steinernema carpocapsae Ade Rosmana a, Merle Shepard b, Prakash Hebbar c, and Anita Mustari a a Cocoa Research Group, Faculty of Agriculture, Hasanuddin University Jalan Perintis Kemerdekaan km 10, Makassar 90245, South Sulawesi, Indonesia Phone (+62) 411 586477, Facs. (+62) 411 587100, E-mail: ; b Clemson University, Coastal Research and Education Center, 2700 Savannah Hwy Charleston, SC 29414 USA c USDA/APHIS/PPQ/EDP, 4700 River Road, Riverdale, MD 20737 USA Submitted 19 October 2009; Accepted 03 June 2010 ABSTRACT INTRODUCTION Cocoa pod borer (CPB; Conopomorpha cramerella) and Phytophthora pod rot (PPR; Phytophthora palmivora) are serious pest and disease on cocoa plantations in Indonesia. Both pest and disease have been controlled with limited success using cultural practices such as pruning, frequent harvesting, sanitation, plastic sleeving, and chemical pesticides. An experiment was conducted on cocoa plantings in Pinrang Regency, South Sulawesi during the wet season of 2008/09 to test the effect of pod sleeving (with transparent degradable and non-degradable plastic bags) and nematode application on CPB and PPR infestation. The nematode, Steinernema carpocapsae (10,000 active juveniles per pod) was sprayed three times at intervals of 10 and 20 days. Pod damage by CPB was observed at harvest time, while PPR disease incidence was evaluated every week until harvest time. Results showed that all pods in the field were infested by CPB as indicated in control samples. Pod sleeving using both non-degradable and degradable plastics significantly reduced pod damage by CPB, from 62.3% in the control treatment compared to 8.4% in the CPB treatment. A combination of pod sleeving and nematode application had a synergistic reduction of pod damage by CPB resulting in totally healthy pods. Pod sleeving with degradable and non-degradable plastics also reduced pod damage by PPR significantly. Pod sleeving with non-degradable plastic suppressed the disease incidence almost zero until 6 weeks after sleeving and the rate of disease incidence was 3.6% per week. However, with degradable plastic, the disease suppression was even longer (7 weeks after sleeving), indicating that the degradable plastic is more effective. Combination of sleeving and nematode application slightly increased PPR infection. Sleeved pods in general had lower rates of PPR infection compared to pods treated with nematode or untreated pods (control). In these two applications, the rate of disease incidence was 7.8% and 8.3% per week respectively. The study implies that biological control using entomopathogenic S. carpocapsae and degradable plastic sleeves are effective and environmentally-friendly to control C. cramerella and P. palmivora on cocoa. Conopomorha cramerella Snellen (Lepidoptera: Gracillariidae) known as cocoa pod borer (CPB) is one of the most important limiting factors to cocoa production in Indonesia and Malaysia (Lim 1992; Wardojo 1996; van Grinsven 2003; Sulistyowaty and Wiryadiputra 2007; Shapiro et al. 2008). The newlyhatched larva tunnels through the floor of the eggshell and bores perpendicular to the pod surface. Larvae live and feed on the pulp and placenta until they reach maturity, then they emerge and pupate (Alba et al. 1985; Rauf 2008). Larval feeding results in pods that may ripen prematurely, with flat, small beans, that are often stuck together in a mass of dried mucilage (Mumford and Ho 1988). Cultural practices such as pruning, frequent and complete harvesting, sanitation, and fertilization are aimed at reducing CPB infestations (Wood 1987; Mumford and Ho1988; Kamaruddin 2000). Chemical control has largely been ineffective, but there is evidence that encouraging ants can provide some biological control (Wood 1987; Teh and Yeow 1995; See and Khoo 1996; Gassa et al. 2003; La Daha et al. 2003; Shapiro et al. 2008). Farmers have resorted to placing plastic sleeves over the young developing pods to prevent CPB from laying eggs on the pods (Moersamdono and Wardojo 1984; Mustafa 2006). This approach offers the best protection from CPB when there may still be 5-15% CPB infestation (Purung, personal comm.). However, the plastic sleeves often pollute the environment by entering streams and other areas. So far, no much information concerning the use of degradable plastic in pod sleeving for controlling pest both in fruits and in cocoa. [Keywords: Theobroma cacao, Conopomorpha cramerella, Steinernema carpocapsae, Phytophthora palmivora, pest control, disease control] 42 Ade Rosmana et al. Biological control of CPB by using entomopathogenic nematodes is promising because nematodes are capable of seeking and killing their host rapidly (Gaugler et al. 1997; Adams and Nguyen 2002; ShapiroIlan et al. 2002). One potential entomopathogenic nematode species is Steinernema carpocapsae which can persist on the pod surface in both the dry and wet seasons and can penetrate the cocoa pods (Rosmana et al. 2009). Plastic sleeves would provide high humidity on pod surface and thus enable nematodes to persist for a longer period of time. However, higher humidity on the pod surface could increase the risk of the incidence of Phytophthora pod rot (PPR) caused by Phytophthora palmivora. The disease plays an important role in the reduction of cocoa production in Indonesia, not only in the wet season but also in the dry season when vectors such as ants exist in the field (McMahon and Purwantara 2004; Rosmana et al. 2006). Purung (personal comm.) found that in the wet season, the development of pod rot was relatively high in sleeved pods. On the other hand, Mustafa (2006) reported that pod sleeving can protect the pods from PPR infection. Nevertheless, the development of pod rot might occur in sleeved pods, because P. palmivora can infect pods before sleeving (Moersamdono and Wardojo 1984). Because of environmental issues associated with the use of non-degradable plastic, in this present work we evaluated the use of degradable plastic sleeves combined with the application of the nematode, S. carpocapsae, for controlling cocoa pod borer and observe its effect on the development of pods and PPR of cocoa. MATERIALS AND METHODS Design of Field Experiment The research was carried out in Pinrang Regency, South Sulawesi, an endemic area of CPB and PPR, from November 2008 until February 2009 during the wet season. This season was correlated with a high infestation of CPB since it was the low season of cocoa pod production with relatively few pods on trees, and with a high intensity of PPR due to high humidity. The experiment used two kinds of plastic sleeves (non-degradable and biodegradable) combined with nematode application. Non-degradable plastic is a transparent polythene sleeve wi (...truncated)