Application of chemical and biological agents for the management of frosty pod rot (Moniliophthora roreri) in Costa Rican cocoa (Theobroma cacao)

Abstract

This article describes two field trials carried out at La Lola, Costa Rica, to assess control measures against frosty pod rot of cocoa (Theobroma cacao) caused by Moniliophthora (Crinipellis) roreri. In the first, factorial, trial the control agents were applied using motorised mistblowers (MMs) and hydraulic sprayers fitted with a narrow angle cone nozzle. There was an interaction between agents and application methods; together with previous application data for the most active fungicide (copper hydroxide), these trials indicate that best yields are achieved with sprays that maximise deposits on pods. We describe the droplet size spectra produced by a Stihl SR400 MM under a range of conditions because this has become the standard method of fungicide application in this series of trials at La Lola. The factor that had the largest effect on droplet size spectrum was the presence or the absence of a detachable baffle plate in front of the air-shear nozzle. In both trials described here, MMs were fitted with baffle plates, a formulation pump and restrictor transmitting 550 mL min 21 to deliver an estimated equivalent of 190 L ha 21 . Copper hydroxide as prophylactic applications at 1500 g a.i. ha 21 have, to date, shown the most consistent (but incomplete) improvement in healthy pod yield. Use of copper fungicides may be cost effective when farm-gate cocoa prices exceed approximately $1.25 kg 21 . In these trials, isolates of the hyperparasitic fungi Clonostachys byssicola and Trichoderma asperellum and two offpatent triazole fungicides (bitertanol and triadimenol) made no significant improvement to healthy yields. The systemic oxathiin fungicide flutolanil, at a dosage of 300 g a.i. ha 21 , appears to protect pods substantially at early stages but gives proportionately less control of M. roreri than copper at later stages of pod development.

Plant extracts containing caffeic acid and rosmarinic acid inhibit zoospore germination of Phytophthora spp. pathogenic to Theobroma cacao

“…are being examined as a biocontrol agents against cacao diseases (Holmes et al, 2004;Bateman et al, 2005). This potential biocontrol agent mycoparasitizes hyphae of Phytophthora spp.…”

Especies de Trichoderma del agroecosistema cacao con potencial de biocontrol sobre Moniliophthora roreri

“…El uso de fungicidas ha sido una práctica poco empleada, debido a las estrategias erráticas de evaluación de fungicidas y al precio fluctuante del cacao (Bateman et al, 2005). También se han establecido programas para el desarrollo de material genético resistente (Phillips-Mora, ArciniegasLeal, Mata-Quiros, & Motomajor-Arias, 2012); sin embargo, no se han obtenido progresos notables en la utilización comercial de clones con resistencia a la enfermedad.…”

“…The use of fungicides has been a scarcely used practice, due to the erratic strategies of fungicide evaluations and to the fluctuating price of cacao (Bateman et al, 2005). Programs for the development of resistant genetic material have also been established (Phillips-Mora, Arciniegas-Leal, Mata-Quiros, & Motomajor-Arias, 2012); however, notable progress has not been obtained in the commercial use of clones with resistance to the disease.…”

Mycoparasitism by Clonostachys byssicola and Clonostachys rosea on Trichoderma spp. from cocoa (Theobroma cacao) and implication for the design of mixed biocontrol agents

“…In fact, the number of isolates in the mixture was negatively correlated with frosty pod rot and witche's broom Soberanis, 2001, 2002). However, the mixed inocula approach was less successful in Costa Rica (Bateman et al, 2005b;Krauss et al, 2003).…”