Witches' broom disease on cocoa in Rondonia, Brazil: basidiocarp production on detached brooms in the field

Abstract

Fruiting of Crinipellis perniciosa was assessed in relation to various climatic factors using dead witches' brooms detached from cocoa, either suspended in the canopy or laid on leaf litter under cocoa. Induction of basidiocarp production occurred over approximately 60 days with rain. Basidiocarps were finally observed on about 85% of brooms in all samples examined and induction of fruiting required at least 17 rainy days, although brooms with a minimum age of 2 years produced basidiocarps about 25 days before brooms with a minimum age of 1 year. Groups of brooms showed distinct cycles of basidiocarp production, and up to 50% of fruiting occurred on dead, attached leaves, Fruiting was reduced on brooms on leaf litter and basidiocarps survived for less time than when brooms were suspended in canopy. Brooms were most productive with moderate amounts of wetness per day, and less than 4 h or more than 20h was inhibitory. No fruiting occurred at mean air temperatures higher than 30°C or lower than 20°C. The microclimate of the litter layer is discussed in relation to reduction of fruiting caused by pruning of brooms.

Witches' broom disease on cocoa in Rondonia, Brazil: pod infection in relation to pod susceptibility, wetness, inoculum, and phytosanitation

“…Numbers of open, turgid basidiocarps were recorded daily on samples of 50 dead brooms with leaves attached and suspended in the cocoa canopy (Rudgard, 1986b). Brooms were cut at random from trees within the experimental site in September 1983 and tied with 10 brooms on each of five strings between wooden supports.…”

“…Inoculum of C. perniciosa is produced from basidiocarps formed on dead diseased parts of cocoa trees, normally the groups of infected shoots (brooms) from which the disease derives its name. The main sources of basidiocarps are vegetative and flower cushion brooms within the canopy and lower branches, and fructification is related to broom wetness derived from rain (Rudgard, 1986b). Pods that become diseased cannot initiate disease in other pods within the same production cycle because of the long latent period (Baker & HoUiday, 1957).…”

“…Temperature and plant surface wetness are known to aflect infection by C. perniciosct in artificial environments (Baker & Holliday, 1957). Temperatures in Rondonia have been shown to be within the required limits throvighout the infection season (Rudgard, 1986b). Surface wetness is derived from rain, or from condensation on pods between 06.30 and about 10.00 h caused by thermal lag (Butler,I9H0).…”

Plant pathology in a developing world

“…Alternate wetting and drying ofthe brooms proved to be a key feature (Rocha & Wheeler, 1982) though within a suitable regime productivity was influenced by the type of tissue, cocoa clone, temperature and light (Rocha & Wheeler, 1985). These results led to the development of a simple but effective system for inducing basidiocarps in the laboratory and, in part, also renewed interest in fruiting of C. perniciosa under field conditions (Rudgard, 1986b).…”

Effects of the fungus Crinipellis perniciosa, causal agent of witches' broom disease, on cell and tissue cultures of cocoa (Theobroma cacao L.)

“…Witches' broom disease of cocoa (Theobroma cacao), caused by the Basidiomycete fungus Crinipellis perniciosa, currently causes severe damage to many cocoa plantations in South America (Rudgard, 1986). There is considerable information concerning the effects of the disease on the host plant (Wheeler, 1985) but much less is known about the effect of the fungus on the cocoa cells and tissue.…”