In-Furrow Applications of Metalaxyl and Phosphite for Control of Pink Rot (Phytophthora erythroseptica) of Potato in New Brunswick, Canada

Abstract

The efficacy of metalaxyl-m (Ridomil Gold 480EC) and phosphite (Phostrol) applied at planting in-furrow against pink rot (Phytophthora erythroseptica) of potato (Solanum tuberosum) ‘Shepody’ and ‘Russet Burbank’ was evaluated in field trials conducted in 2005 and 2006 in Florenceville, New Brunswick, Canada. Inoculum made from a metalaxyl-m-sensitive isolate of P. erythroseptica from New Brunswick was applied either in-furrow as a vermiculite slurry at planting or as a zoospore drench in soils adjacent to potato plants in late August. After harvest, the number and weight of tubers showing pink rot symptoms were assessed and expressed as percentages of the total tuber number and total weight of tubers. Metalaxyl-m applied in-furrow was significantly more effective against pink rot than phosphite. The mean percentage of diseased tubers as a percentage of total tuber weight was 1.5% (2005) and 1.2% (2006) for metalaxyl-m-treated plots and 9.6% (2005) and 2.8% (2006) for phosphite-treated plots, a percentage similar to that obtained in inoculated control plots with no fungicide treatment. The mean percentage of diseased tubers expressed as a percentage of the total number of tubers was 1.7% (2005) and 1.3% (2006) for metalaxyl-m-treated plots and 10.1% (2005) and 3.1% (2006) for phosphite-treated plots. Disease incidence was significantly higher using the late-season inoculation technique (respective means in 2005 and 2006 were 9.9 and 3.8% diseased tubers, by weight, and 10.6 and 3.9%, by number) than with the in-furrow inoculation method (respective means in 2005 and 2006 were 3.3 and 0.7% by weight, and 3.7 and 1.3%, by number). The potato cv. Shepody was significantly more susceptible to pink rot (9.9 and 3.3% diseased tubers, by weight, in 2005 and 2006, respectively, and 10.6 and 3.9%, by number) than Russet Burbank (respective means in 2005 and 2006 were 3.4,% and 1.2%, by weight, and 3.7,% and 1.2%, by number). Our findings indicate that metalaxyl applied in-furrow at planting is a viable option for control of pink rot caused by metalaxyl-sensitive strains of P. erythroseptica, whereas phosphite was ineffective.

Phosphite uptake and distribution in potato tubers following foliar and postharvest applications of phosphite-based fungicides for late blight control

“…Late blight, caused by the oomycete Phytophthora infestans (Mont.) de Bary is considered the most devastating and difficult disease to control in potatoes (Miller et al , ; Al‐Mughrabi et al , ; Haverkort et al , ; Taylor et al , ; Gachango et al , ; Nowicki et al , ). P .…”

Coffee‐leaf extract and phosphites on the curative control of powdery mildew in eucalyptus mini‐stumps

“…Other studies have demonstrated the inefficacy of potassium phosphite in the control of plant pathogens, such as Colletotrichum gloeosporioides in apple trees (Ara ujo et al 2010), Verticillium dahlia in cacao trees (Ribeiro et al 2006) and even oomycetes, such as Phytophthora erythroseptica in potatoes (Al-Mughrabi et al 2007) and P. infestans in tomatoes (Nascimento et al 2008). Other studies have demonstrated the inefficacy of potassium phosphite in the control of plant pathogens, such as Colletotrichum gloeosporioides in apple trees (Ara ujo et al 2010), Verticillium dahlia in cacao trees (Ribeiro et al 2006) and even oomycetes, such as Phytophthora erythroseptica in potatoes (Al-Mughrabi et al 2007) and P. infestans in tomatoes (Nascimento et al 2008).…”

“…Phosphites of Cu, Zn and K/Mn were also more effective than the fungicide in the control of powdery mildew in the eucalyptus seedlings, while the potassium phosphite was not efficient. Other studies have demonstrated the inefficacy of potassium phosphite in the control of plant pathogens, such as Colletotrichum gloeosporioides in apple trees (Ara ujo et al 2010), Verticillium dahlia in cacao trees (Ribeiro et al 2006) and even oomycetes, such as Phytophthora erythroseptica in potatoes (Al-Mughrabi et al 2007) and P. infestans in tomatoes (Nascimento et al 2008). However, Bizi et al (2008) observed that potassium phosphite at 0.6 ml/l and copper phosphite at 0.2 ml/l did not control powdery mildew in eucalyptus.…”

Factors influencing the performance of phosphites on the control of coffee leaf rust

“…The dependence of the accompanying cation in the efficiency of phosphite in disease control has been recorded in previous studies. While Cu and Zn phosphites were effective in controlling white mold in common bean plants (Fagundes-Nacarath et al 2018) and powdery mildew in eucalyptus seedlings (Silva et al 2013), K phosphite was ineffective in the control of anthracnose in apple trees (Araujo et al 2010), Verticillium wilt of cacao trees (Ribeiro Júnior et al 2006), pink rot in potatoes (Al-Mughrabi et al 2007) and late blight in tomatoes (Nascimento et al 2008). In the present study, Cu phosphite provided the most consistent results in terms of CLR control since this phosphite was the most efficient in decreasing both TNP per leaf and CLR, regardless of the dose and washing treatments.…”