Production of avocado trees infected with Phytophthora cinnamomi under different management regimes

Abstract

Avocado root rot is the most important disease of this fruit crop worldwide. This pathology may be caused by several biotic and abiotic agents, with the oomycete Phytophthora cinnamomi being the pathogen more frequently associated with poor phytosanitary conditions. There are disease control methods available that can reduce disease severity and allow plants to recover; however, they are not consistently and promptly applied. In addition, only chemical products are used by farmers as the preferred management method. This research aimed to evaluate different root rot management strategies in a commercial orchard. Data suggest that individual control methods are not as effective as when they are applied in combination, as in the T8 treatment (metalaxyl + mancozeb applied in drench; injection of potassium phosphite to each plant stem; potassium silicate applied in drench; addition of a layer of organic mulch and incorporation of 10 kg of composted substrate, both applied to the ground around the base of each tree). Using this strategy, the area under the disease progress curve for the avocado root rot was reduced by up to 68.6%, and the extra-quality avocado fruit class increased by as much as 44% compared to the diseased control plants (T0) (P < 0.01). With the combined treatment T8, farm income showed a 9.5-fold increase, probably due to an increase in the percentage of viable roots by up to 9.4-fold, which would have improved nutrient and water uptake.

Phytophthora cinnamomi

“…The scale of P. cinnamomi distribution, its ability to survive for years in soil or symptomless plants, and the extent of plant susceptibility make the management of P. cinnamomi diseases challenging and difficult. The benefits of implementing integrated strategies have been demonstrated for the management of avocado root rot, the most important disease of avocado worldwide (Ram ırez-Gil et al, 2017). A combination of drenching in metalaxyl, mancozeb and silicate, with phosphite injection, addition of compost to the soil and mulching with organic material reduce disease occurrence and increase the production of first class fruit by almost 70% and 44%, respectively, relative to untreated controls.…”

Avocado wilt complex disease, implications and management in Colombia

“…Another active ingredient that is commonly used is metalaxyl, which is applied as a drench to the soil ( Figure 6K) or in powder form to lesions created or to cankers in the base of the stem of affected trees ( Figure 6E and 6M). The use of phosphite and metalaxyl have presented good results in greenhouse and field conditions in the management of P. cinnamomi Leal et al, 2014;Ramírez-Gil et al, 2014b;Tamayo, 2007).…”

“…In Colombia, various studies have been performed with the objective of evaluating the effects of distinct microorganisms on reducing P. cinnamomi, identifying important metabolites with potential use in commercial products (Ramírez et al, 2015;Granada et al, 2018), but application in yields has been reduced. In this regard, Ramírez-Gil et al (2014b) evaluated, under greenhouse conditions, the interaction of Glomus fasciculatum, Trichoderma harzianum, Pseudomona sp. and P. cinnamomi.…”

Harmonising the fields of invasion science and forest pathology

“…Another classic example is the impact of the 'biological bulldozer' P. cinnamomi in Australia. Management of this pathogen presents greater challenges in natural ecosystems (Dunstan et al 2010) than in avocado and other crop plants (Drenth and Guest 2004;Ramírez-Gil et al 2017).…”