This sampling method uses the presence-absence method. Rather than counting the number of mites, scouts simply need to determine whether mites occur or do not occur on the collected leaves

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Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory June 2010ENT-60SF-06Utah Pests Sampling Form: Spider and Predatory MitesPresence-Absence Sampling MethodOrchard Block:_________________________________________  Variety: _________________________Date: _______________________________  Stage of Bud Development: _________________________This sampling method uses the presence-absence method.  Rather than counting the number of mites, scouts simply need to determine whether mites occur or do not occur on the collected leaves.Spider Mites Predatory MitesTreeNumber of Leaves out of 10 with at least one MiteEstimated Number of Mites/Leaf (from look-up table)Number of Leaves out of 10 with at least one MiteEstimated Number of Mites/Leaf (from look-up table)12345678910Total Number of Mites/LeafTotal Number of Mites/LeafAverage Number of Mites per leaf (divide above sums by 10)Average Number of Mites per leaf (divide above sums by 10)When and How Often to SampleBeginning in mid-June, monitor for spider mites every 1 – 2 weeks through mid-September.  During the hottest months, monitor weekly.Materials1.  Plastic ziploc bags in which to collect leaves2.  16 – 20x hand lensInstructions1.  Choose representative orchard blocks of each fruit type for sampling. For orchard-specific pest control, all orchards should be sampled.2.  Randomly select 10 trees scattered throughout a 2- to 5-acre block.  Include trees where known problems ex-ist, or where mite infestations may occur sooner, such as drought-prone areas or stressed trees.3.  On each sampling date collect 10 leaves from each of 10 trees (100 leaves total).  Select leaves from repre-sentative areas of the entire tree canopy.4.  Keep leaves from each tree in separate bags in order to identify “hot spots.”5.  Check both sides of each leaf with a hand lens, look-ing for spider mites and predatory mites.6.  Record the number of leaves from each tree infested with each type of mite (spider and predatory).  Note: It is not necessary to count the number of mites.7.  Use the look-up tables to estimate the number of spi-der and predatory mites per leaf. 8.  Obtain the average mite density by adding all 10 esti-mated mite densities and dividing by 10.  Take notice of trees with higher than average densities as these may be “hot spots.”9.  NOTE:  The same leaf collections can be used to moni-tor for western tentiform leafminer in apple and cherry.Identification of Spider and Predatory MitesSpider Mites:  1/60-inch, oval-shaped; yellow-green in color, turning brown with age; twospotted has two black spots on back, McDaniel has multiple spots; only moves forwardPredatory Mites:  similar size but shinier and teardrop-shaped; longer legs than spider mites; clear to yel-low in color; moves forward and backward quickly through spider mite colonies, looking for preyTreatment ThresholdsApple: Treat if average number of mites per leaf is >10 and there is <1 predator per leaf.Pear: Treat if average number of mites per leaf is >5 and there is <1 predator per leaf.Mite Look-up TablesTwospotted and McDaniel Spider MitesTetranychus urticae and T. mcdanieliNumber of Leaves out of 10 with at Least One Mite PresentEstimated Number of Mites Per Leaf1 0.12 0.43 0.74 1.15 1.76 2.47 3.58 5.29 8.810 ---Predatory MiteGalendromus (Typhlodromus) occidentalisNumber of Leaves out of 10 with at Least One Mite PresentEstimated Number of Mites Per Leaf1 0.12 0.33 0.54 0.85 1.16 1.57 2.18 3.09 4.610 ---For more information, see the Web-spinning Spider Mites.Spider and Predatory Mites Sampling InstructionsUtah State University is committed to providing an environment free from harassment and other forms of illegal discrimination based on race, color, religion, sex, national origin, age (40 and older), dis-ability, and veteran’s status. USU’s policy also prohibits discrimination on the basis of sexual orientation in employment and academic related practices and decisions.  Utah State University employees and students cannot, because of race, color, religion, sex, national origin, age, disability, or veteran’s status, refuse to hire; discharge; promote; demote; terminate; discriminate in compensation; or discriminate regarding terms, privileges, or conditions of employment, against any person otherwise qualified. Employees and students also cannot discriminate in the classroom, residence halls, or in on/off campus, USU-sponsored events and activities.  This publication is issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Dept. of Ag., Noelle E. Cockett, Vice President for Extension and Agriculture, Utah State University.Page 2UPPDL, 5305 Old Main Hill, Logan UT 84322, utahpests.usu.edu T: 435.797.2435  F: 435.797.8197Fact Sheet Series:  Insects - Tree Fruit Sampling FormsPrecautionary Statement:  Utah State University Extension and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document.  All pesticides are labeled with ingredients, instructions, risks, and registered crops or other hosts.  The pesticide applicator is legally respon-sible for proper use.  USU makes no endorsement of the products listed herein.

Spider and Predatory Mites Sampling Form

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Spider and Predatory Mites Sampling Form

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