Chemical control of two Phytophthora species infecting the canopy of Monterey pine (Pinus radiata)

Abstract

Twelve active ingredients were screened for their ability to control foliage disease caused by Phytophthora kernoviae and Phytophthora pluvialis. Inhibition of mycelial growth and sporangial production of both pathogens were assessed in in vitro assays after exposure to three concentrations of each active ingredient. While most of these active ingredients inhibited mycelial growth in vitro, due to their widespread use, phosphite, copper oxychloride and metalaxyl-M were selected for further study. Four rates of each active ingredient were applied to two Pinus radiata genotypes, and detached needle assays at 6 and 90 days post-treatment were used to determine treatment efficacy and persistence. Untreated needles showed significantly larger lesions than all fungicide-treated needles after exposure to P. pluvialis or P. kernoviae on both sampling dates. Efficacy and persistence of the three active ingredients did not increase with increase in concentration. Larger lesions were formed on more susceptible genotype after inoculation with both Phytophthora species, even when higher rates of active ingredients were applied. Phosphite, copper oxychloride and metalaxyl-M have potential to protect commercially planted P. radiata from these two Phytophthora species.|

Impact of weather variables and season on sporulation of Phytophthora pluvialis and Phytophthora kernoviae

“…15 years old. Based on the results reported here, copper fungicides, shown to be effective against Phytophthora pluvialis and P. kernoviae in laboratory assays (Rolando et al, 2017, 2019), may be most effective if applied between March and May (Autumn). Copper persists on pine needles for ca.…”

“…Copper persists on pine needles for ca. 3 months (Rolando et al, 2017), and a spray towards the end of April should protect foliage until at least July, limiting the opportunity for disease to develop. Though further field‐based research is needed before precise operational spray recommendations can be made.…”

“…Little else is known about the drivers of epidemics of needle diseases caused by Phytophthora pluvialis and P. kernoviae on Pinus radiata , limiting the development of a system of disease management. However, several compounds, including copper oxychloride, have been shown to be effective against both pathogens in controlled inoculation experiments (Rolando, Dick, Gardner, Bader, & Williams, 2017; Rolando, Somchit, Bader, Fraser, & Williams, 2019). Copper fungicides have been used to control dothistroma needle blight in New Zealand pine plantations since the mid‐1960s (Bulman et al, 2016).…”

High-Throughput Chemical Screening Identifies Compounds that Inhibit Different Stages of the Phytophthora agathidicida and Phytophthora cinnamomi Life Cycles

“…actinidiae (Cameron and Sarojini, 2014; Gould et al, 2015). Similarly, copper fungicides are widely used by the New Zealand forestry industry for control of dothistroma needle blight (Bulman et al, 2013) and they have recently been shown to be effective against Phytophthora pluvialis (Rolando et al, 2016). However, concerns around soil accumulation and toxicity limit the use of copper sprays in natural environments (Wightwick et al, 2008; Komarek et al, 2010; Kiaune and Singhasemanon, 2011).…”

“…Exacerbating the effects of Phytophthora infection is the fact that these species are notoriously difficult to control. While Phytophthora share many traits with the true fungi, they are phylogenetically distinct enough to lack many of the canonical molecular targets of labeled fungicides ( Rolando et al, 2016 ). For example, Phytophthora species lack the biosynthetic pathways for ergosterol and a chitin-based cell wall.…”