Population Density and Phenology ofTetranychus urticae(Acari: Tetranychidae) in Hop is Linked to the Timing of Sulfur Applications

Abstract

The twospotted spider mite, Tetranychus urticae Koch, is a worldwide pest of numerous agronomic and horticultural plants. Sulfur fungicides are known to induce outbreaks of this pest on several crops, although mechanisms associated with sulfur-induced mite outbreaks are largely unknown. Studies were conducted during 2007-2009 in Oregon and Washington hop yards to evaluate the effect of timing of sulfur applications on T. urticae and key predators. In both regions, applications of sulfur made relatively late in the growing season (mid-June to mid-July) were associated with the greatest exacerbation of spider mite outbreaks, particularly in the upper canopy of the crop. The severity of mite outbreaks was closely associated with sulfur applications made during a relatively narrow time period coincident with the early exponential phase of spider mite increase and rapid host growth. A nonlinear model relating mean cumulative mite days during the time of sulfur sprays to the percent increase in total cumulative mite days (standardized to a nontreated plot) explained 58% of the variability observed in increased spider mite severity related to sulfur spray timing. Spatial patterns of spider mites in the Oregon plots indicated similar dispersal of motile stages of spider mites among leaves treated with sulfur versus nontreated leaves; however, in two of three years, eggs were less aggregated on leaves of sulfur-treated plants, pointing to enhanced dispersal. Apart from one experiment in Washington, relatively few predatory mites were observed during the course of these studies, and sulfur-induced mite outbreaks generally occurred irrespective of predatory mite abundance. Collectively, these studies indicate sulfur induces mite outbreaks through direct or indirect effects on T. urticae, mostly independent of predatory mite abundance or toxicity to these predators. Avoidance of exacerbation of spider mite outbreaks by sulfur sprays was achieved by carefully timing applications to periods of low spider mite abundance and slower host development, which is generally early to mid-spring for hop.

Impact of sulfur dust application on the abundance of two important coccinellid predators in marrow fields

“…In contrast, our results were partially matched with that reported by Biddinger et al (2009), as they mentioned that the use of chemical control, even insect growth regulators or elemental sulfur, can be very harmful to Stethorini and other biological agents. Gesraha and Ebeid Bulletin of the National Research Centre (2019) 43:34 Woods et al (2012) mentioned that a significant differences in the abundance of Stethorous spp.-as predatory insect-in the levels of leaves that are treated with sulfur compared with untreated ones, presumably the positive effect of sulfur on predatory insects, were associated with greater prey abundance provoked by sulfur treatment effects, i.e., sulfur kill the predator, which gave the opportunity to the prey to propagate.…”

Organic Farming Sharpens Plant Defenses in the Field

“…Conventional farming methods often largely rely on chemical insecticides for the control of herbivorous insects (e.g., Soffe, 2002;Stockdale et al, 2002;Klonsky, 2012). This approach can inadvertently disrupt biological control and worsen pest outbreaks when broad-acting chemicals kill natural enemies (Penman and Chapman, 1988;Prischmann et al, 2005;Woods et al, 2012).…”

Phenology and abundance of date palm mite Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) in Riyadh, Saudi Arabia

“…Phenology is defined as “the timing of periodic life history events”, such as diapause, molting, and time of emergence or infestation ( Hodgson et al, 2010 , Visser, 2008 ). The factors influencing the phenology of mites include the photoperiod ( Visser, 2008 ), acaricide applications ( James, 2000 , Kim and Lee, 2003 , Woods et al, 2012 ), the presence of predators ( Walton et al, 2010 ), alternate hosts ( James, 2000 , Kim and Lee, 2003 ), and the phenology of the host plant ( Herms, 2004 , Palevsky et al, 2003 , Palevsky et al, 2004 , Samah and Chermiti, 2010 , Arnemann et al, 2015 , Dar et al, 2015 ).…”

“…The phenology of economically important insect and mite pests is studied to understand the effect of changing climate on their life history traits and to practice integrated management ( Nietschke et al, 2007 , Richardson et al, 2009 ). In this regard, numerous bio-ecological studies concerning seasonal changes have been conducted in insects ( Rock et al, 1993 , Menzel et al, 2006 , Doi et al, 2008 , Doi and Takahashi, 2008 , Hodgson et al, 2010 ) and mites ( Kim and Lee, 2003 , Walton et al, 2010 , Vangansbeke et al, 2015 , Palevsky et al, 2010 , Patankar et al, 2012 , Hardman et al, 2005 , James et al, 2001 , Woods et al, 2012 ). As all developmental stages of a species are not vulnerable to control and management practices, phenology data highlights the susceptible pest stages ( Ascerno, 1991 , Visser, 2008 ).…”