Washington State University

Entomology (subpage)

Twospotted Spider Mite in Hop

Twospotted spider mite, Tetranychus urticae, causes damage to hops through its feeding action. It is a serious and perennial threat in virtually all Pacific Northwest hop yards. Infestations of T. urticae can lead to yield and quality losses in hops and may contribute to detrimental flavor characteristics. 

2013 Miticide Resistance Studies

WSU Masters degree candidate Tara Piraneo details a series of experiments investigating the response of T. urticae to varying levels of abamectin, bifenazate, and bifenthrin in her thesis, Acaricide Resistance of the Two-Spotted Spider Mite in Pacific Northwest Hops. 

2011 Compounds Evaluated: Early Season

In our 2010 trials (details below), we noticed treatment effects in mite populations following the early-season treatments we made for hop aphids. In 2011, we deliberatedly evaluated mite impacts from the following aphid treatments.

Early season compounds 2011

2011 Early Season Results: Mites

Bar Chart Early Season Treatment Mites 2011


2011 Early Season Results: Mite Eggs

Bar Chart Mite Eggs Early Season 2011

2011 Candidate Compounds: Late Season

The following treatments were slated for 4 August 2011 application.

2011 Candidate Mite Compounds

2011 Mite Counts

Due to extremely low mite populations in 2011, as documented below, single-compounds and rotational program efficacy tests were impractical this season.

2011 Mite Counts

2010 Compounds Evaluated: Early Season

The following compounds were applied for hop aphid control in 2010, but impacts were also evaluated on mites and are presented in the two charts following.

2010 Aphid Compounds

2010 Early Season Results

We were not surprised to see imidacloprid (Provado) flare mites post-application, but flaring also occurred in several other treatments. Spirotetramat (Ultor) did not flare mites, and was very effective on aphid control. It was therefore slated for further study in 2011.


2010 Compounds Evaluated: Late Season

These products were evaluated specifically for their impacts on mites in 2010.

2010 Mite Compounds

2010 Late Season Results: Mites

2010 Mite Results

2010 Late Season Results: Mite Eggs

2010 Mite Egg Results

2010 Rotational Program Compounds

To evaluate controls applied in a rotational program, we tracked plots in which the compound in the first column (applied 8-2-10) was followed by application of a different compound, shown in the third column, on 8-31-10.

2010 Rotational Program

2010 Rotational Program Results

2010 Rotational Trial Results

2010 Idaho Efficacy Trials

Six miticides and one aphicide were evaluated for efficacy at the Southwest Idaho Research and Extension Center in Parma, Idaho. Except for BeLeaf, which targets hop aphid, all products target twospotted spider mites. Neither spider mite nor aphid populations developed damaging levels in 2010. Mean spider mite and spider mite egg numbers did not exceed 2 per leaf on treated or control plots. Mean hop aphid numbers did not exceed 4 per leaf on treated or control plots. These numbers were not high enough to detected significant differences in numbers of these pests between treatments.


Rate (Oz. /

Spider mites

Spider mite eggs

Hop aphids

Acramite 4 SC


0.4 ± 0.23

1.3 ± 0.51

1.8 ± 0.43

Agri-Mek 0.15 EC


0.5 ± 0.30

1.7 ± 0.85

2.2 ± 0.49

BeLeaf 50 SG


0.3 ± 0.07

0.7 ± 0.26

1.4 ± 0.54

Envidor 2 SC


0.7 ± 0.31

1.4 ± 0.74

2.2 ± 0.45

Onager 1E


0.3 ± 0.14

1.0 ±  .55

1.2 ± 0.0.27

Ultiflora (Mesa)


1.2 ± 0.71

1.6 ± 0.95

1.7 ± 0.37



0.7 ± 0.34

1.3 ± 0.49

2.0 ± 0.41



0.92 ± 0.21

1.7 ± 0.44

3.9 ± 0.97


Entomology subpage

This page is designed to provide additional information pursuant to the Entomology component of the overall project discussed on the Washington State University website http://hopmintstress.wsu.edu .

It is not designed to be viewed or utilized independently of that website.

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TSSM Images

Spider mite

Twospotted spider mite, Tetranychus urticae

TSSM adult female

Adult female (note prominent black spots on each side of abdomen); adults are approximately 1/50-inch long

TSSM adult male

Adult male; males are approximately 3/4 the size of females and have a more pointed abdomen

TSSM adult, nymphs, and eggs

Adult, nymphs, and eggs; eggs are clear to pearly-white spheres approximately 1/200-inch in diameter

TSSM Damage

TSSM-damaged brown hop bines

Brown bines resulting from TSSM damage

TSSM-damaged hop cones

Browned and stunted hop cones caused by TSSM feeding

Dried out hop bines from TSSM damage

Desiccated bines resulting from TSSM feeding

TSSM-damaged hop leaf stippling

Stippled appearance of hop leaves indicates TSSM damage

Webbing from TSSM

Webbing on hop leaf indicates presense of TSSM

Washington State IPM Coordinator, WSU Irrigated Agriculture Research & Extension Center, Prosser WA 99350, 509-786-9287