Efficacy and Induction Resistance of Neem Extract and Mancozeb 80 Wp on Physoderma Brown Spot and Physoderma Stalk Rot Diseases of Corn (Zea mays) caused by Physoderma Maydis in Far North Cameroon

Ngoh D J Patrice,Ambang Zachee,Tenyang Noel,Djongnang Gabriel,Ntatsinda C Durel,Mbou T P Rony,Deurnaye Placide,Yamagui Rita,Djile Bouba,Tene T P Martial

doi:10.33687/phytopath.010.02.3553

Abstract

Corn (Zea mays) is one of the most widely spread cereals in the world. However, in the Far North Region of Cameroon, the incidence of some maize diseases progress because of farming practices and climate change (rainfall). This work aims to evaluate effect and resistance stimulation of neem extract and Mancozeb fungicide on Brown Spot (PBS) and Stalk Rot (PSR) diseases of corn due to Physoderma maydis in field condition. The experimental design was a two-factor split-plot. The treatments were a combination of Control (T), Mancozeb (Mz) at the concentration of 6g/L and aqueous extract of neem seeds (AENS) at the concentration of 50g/L with CMS 9015 and CMS 8704 varieties. Incidence, severity, rainfall, Area Under Disease Progress Curve (AUIPC, AUSiPC) were recorded. Phenol and protein rates, enzymatic activity of Polyphenol oxidase (PPO), peroxidase (POX) and glucanase were carried out. Stalk length and yield were evaluated. Incidence and severity of Physoderma Brown Spot (PBS) and Physoderma Stalk Rot (PSR) increased with time and environmental conditions (rainfall). The highest disease incidence was observed in the control treatments with both diseases, 52.39 and 37.67 % respectively for Brown Spot and Stalk Rot in CMS8704 variety and lower with AENS, 13.5 and 36.01%. AENS reduced PBS incidence and severity by 23.1 and 19.9 %, respectively and Mz by 9.3 and 18.1 %. The AUIPC and AUSiPC of PBS and PSR remained lower with AENS treatment during the growing season and higher with the other treatments. The highest phenol and proteins rates (8.81 and 25.1 mg/g/FM) were recorded for the AENS treatment in CMS9015 and CMS8704 variety, respectively. Enzymatic activity was more enhanced in CMS8704 variety with AENS. 4.22 A470/min/g, 1.55 A470/min/g and 1.15 µmole/min /g were recorded respectively for PPO, POX, and Glucane activities. Stalk length was higher in AENS and Mancozeb treatments with variety CMS8704 (125.13 and 123 cm respectively). A yield increase of 7.44% was obtained in the AENS treatment. The combination or not of aqueous neem extract and CMS8704 could be used in the integrated control of PBS and PSR of maize

Highlights

Maize is the most cultivated plant and the first cereal produced after wheat and rice in the world (Li et al, 2018)
The Area Under Disease Incidence Progress Curve (AUIPC) and Area Under Disease Severity Progress Curve (AUSiPC) of Physoderma Brown Spot (PBS) and Physoderma Stalk Rot (PSR) remained lower with aqueous extract of neem seeds (AENS) treatment during the growing season and higher with the other treatments
Enzymatic activity was more enhanced in CMS8704 variety with AENS. 4.22 A470/min/g, 1.55 A470/min/g and 1.15 μmole/min /g were recorded respectively for Polyphenol oxidase (PPO), POX, and Glucane activities

Summary

Introduction

Maize is the most cultivated plant and the first cereal produced after wheat and rice in the world (Li et al, 2018). Cameroon is the thirty-fifth corn-producing country globally, with 2.100 thousand tons in 2020 (FAO, 2020) This production could not satisfy national demand, which stood at a little over 2.8 million tonnes. In the Far North Region of Cameroon, this deficit is due to poor farming practices by farmers, inability to buy fertilizers, lack of land, biotic constraints (diseases and pests, choice of seed varieties) and abiotic constraints (climate change, scarcity of rainfall, soil poverty) (MINADER, 2019) To solve this problem, corn growers are looking for a sustainable alternative by using green and organic fertilizers involving animal dung (chicken droppings and cow dung) to promote microbial activity and soil fertility in the soil (Reid et al, 2001; Veresoglou et al, 2012). Research reports indicate diseases due to fungi or bacteria or have been reported in Cameroon on maize, affecting its quantity and quality (William Norbert et al, 2018; Mboussi et al, 2016; Ngoh dooh et al, 2019)

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