Diseases and Insect Pests associated with Cashew (Anacardium occidentale L.) Orchards in Ghana

Abstract

Cashew (Anacardium occidentale L.), a recently recognized cash crop in Ghana, is an economically export oriented crop that plays a helping role in the Ghanaian economy in diverse ways. Owing to its importance, surveys were conducted in some major cashew producing communities in Dormaa and Berekum West District of the Bono region to assess the problems of insect pests and diseases associated with this economic tree across the study area. Diseased samples showing varying degrees of symptoms were taken for isolation and identification using morphological method. Insect pests were also assessed and identified. The results showed Colletotrichum gloeosporioides species complex to be associated with anthracnose, leaf lesions or spots, gummosis of twigs and stems and regressive die-back; Lasiodiplodia theobromae was found to cause stem and twig gummosis, blight, die-back of twigs and inflorescence; Pestalotia sp. was associated with Pestalotia leaf spot. Others, such as Penicillium sp., powdery mildew, Curvularia lunata, Cephaleuros sp. (red rust- algal leaf spot), mushroom and lichens were also found to be associated with the cashew orchards in the study area. Anthracnose, gummosis, algal leaf, and stem spots (red rust) and cashew kernel infection by Curvularia lunata constituted the major diseases of cashew in ascending order in the study area. The insect pests identified included Oecophylla smaragdina, Anoplocne miscurvipeson, Pseudotheraptus devastans, Pachnoda cordata, Pachnoda marginata, Helopeltis bug, Helopeltis schoutedeni, Planococcus sp., Lamida moncusalis, Odontotermes sp., Aphis sp., Analeptes trifasciata. Some unidentified pathogens, pests and other abnormalities were also observed.

Preliminary experiments on potential use of blue monochromatic light for identification of cashew diseases

“…The isolates were further confirmed by reproductive structures observation under the microscope at 10x; 40x e 100x magnifications as necessary and visually compared previously published pictorial keys (Menge & Shomari, 2016;Udayanga et al, 2011;CABI, 1983;Nakapalo et al, 2017;Wonni et al, 2017). For the O. anacardii, being obligate parasite (Muntala et al, 2021) no cultures were made. Disease signs and symptoms (Majune et al, 2018, Nene et al, 2020Freire et al, 2002) were satisfactory for identification purpose.…”

“…The biotrophic fungus (O. anacardii) (Muntala et al, 2021) plant/pathosystem was found to induce significantly higher absorption of blue light than the necrotrophic fungi (Dominic et al, 2014;Martins et al, 2018) Septoria spp. and Cryptosporiopsis spp, in all three experiments.…”

Disease-Causing Agents in Cashew: A Review in a Tropical Cash Crop

“…Cashew anthracnose may fall into this challenging issue because pathogen molecular identifications performed up to now were mostly based on ITS [e.g., 51,53]. Data from our study highlighted C. gloesporioides as the only causal agent of anthracnose in cashew described in India [59], West Africa [60,61], and Mozambique (East Africa [51]); while in Brazil, seven Colletotrichum species, namely C. chrysophilum, C. fragariae, C. fructicola, C. gloeosporioides, C. queenslandicum, C. siamense, and C. tropicale [14,62], were associated with cashew anthracnose. A major difference between studies in Brazil and the remaining countries/regions was the use of a multilocus phylogeny with resolving power to identify other Colletotrichum species beyond C. gloesporioides.…”