Effects of selected pesticides and adjuvants on germination and vegetative growth of Phomopsis amaranthicola, a biocontrol agent for Amaranthus spp.

Abstract

Summary Phomopsis amaranthicola, a bioherbicide agent for Amaranthus spp., was tested in vitro for its compatibility with commercial formulations of 16 adjuvants, 24 herbicides, nine fungicides and four insecticides at 2X, 1X (highest labelled product dose rate), 0.75X, 0.5X and 0.25X concentrations. These chemicals were tested for their effects on spore germination. Selected herbicides and fungicides at 1X were also tested for their influence on colony growth and sporulation. All tested compounds were finally categorized in compatibility classes regarding germination, mycelial growth and sporulation such as low, medium and high compatibility. High compatibility in terms of germination and fungal colony growth was only observed with the herbicide bentazone. Many of the adjuvants tested were highly compatible in the germination studies. Most fungicides and insecticides had medium and low compatibility with P. amaranthicola. Effects of pesticides on spore germination did not fully correspond with their effects on colony growth. Thus, it is possible to integrate the use of P. amaranthicola with some herbicides, fungicides, insecticides and adjuvants but not others. A case‐by‐case selection of application methods, such as tank‐mix or sequential application, along with proper timing of applications of the fungus and the chemical agents will be necessary.

Sensitivity of four isolates of <i>Clonostachys rosea</i> to pesticides used in the strawberry crop in Brazil

“…22) As abamectin, fenpropathrin, and thiamethoxam had a moderate inhibitory e ect, their eld application may be combined with that of C. rosea. Malathion was the most toxic to C. rosea, as found with Phomopsis amaranthicola 14) and Paecilomyces fumosoroseus. 15) e active ingredient of malathion has no antifungal activity; its e ect may be more related to the inert compounds in the formulation.…”

“…8,12,13) Both growth and germination were reduced by the fungicides; growth was more a ected than germination. A pesticide may di erentially a ect spore germination and mycelial growth 14) and these e ects may vary according to the fungal species. 15,16) It is worth considering what process, conidial germination or mycelial growth, is more hindered.…”

“…ey can a ect di erentially antagonistic fungal species. 14,[17][18][19][20] For instance, the isolate C47 of C. rosea was highly sensitive to prochloraz, slightly sensitive to carboxin and thiram, and insensitive to guazatine and triticonazole. 21) Fungi di er in their sensitivity to pesticides of the same chemical class or same mode of action, 16) and we cannot generalize regarding the sensitivity of a species to a pesticide.…”

Unexpected Side Effects of Herbicides: Modulation of Plant-Pathogen Interactions

“…Reports of both enhanced and reduced disease severity have been published and glyphosate seem to have preventative and curative properties. Furthermore, the formulation and adjuvants used to enhance the efficiency of the active compound can dramatically affect germination, growth, and propagation of fungal plant pathogens (Smith & Hallett, 2006;Weaver et al, 2006;Weaver, et al, 2009;Wyss et al, 2004). Interestingly, glyphosate has also been reported to www.intechopen.com control mammalian pathogenic fungi (Nosanschuk et al, 2001) and was active against apicomplexan parasites that cause diseases such as malaria and toxoplasmosis (Roberts et al, 2002).…”

“…These results suggest that timing of glyphosate application in relation to combined treatment with a bioherbicide is important. Wyss et al (2004) reported that certain pesticides and their adjuvants affected spore germination and growth of Phomopsis amaranthicola, an effective bioherbicides against Amaranthus species. Several herbicides such as glyphosate had also negative effects on spore germination of P. setariae (Peng & Byer, 2005).…”