Mid-late Season Pest Management for Day Neutral Strawberries Small Fruit Conference, 11-29-2018 Julie Pond, Peerbolt Crop Management
Pests of concern in Day Neutral production: Thrips Lygus Bug Spotted Wing Drosophila Twospotted Spider Mite
General comments Written recommendations for treatment thresholds typically low and if followed to the letter could lead to over-treatment and more problems with the disruptions caused by insecticides There will be a lot of variability in pest management practices from farm to farm due to grower markets, overall growing approach, field size, etc However actions for these pests needs to be done before damage is visible so either regular field scouting is needed for advanced warning & preventative measures or a calendar based system. If the natural controls on a potential pest species are disrupted by an insecticide for another pest secondary pest outbreak is likely. Rotate chemistry all season long!
Thrips Adults: Small (1-2mm), light yellow/tan narrow, winged insect. Overwinter as adults in leaf detritus Misshapen blossoms and bronzes fruit due to sucking of floral cells Full lifecycle can happen in two weeks = multiple generations in season 100s of host plant species allow population movement from one host to next
Thrips Management Biological/Cultural Beneficial Insects lack of research: Minute Pirate Bugs Lacewing Add alternate host flowering around field edges (but refrain from alternate hosts that will harvest before strawberry crop) Cool, wet weather patterns during bloom suppress populations Consider reflective mulch interferes with ability to locate plants/flowers
Thrips Management Minute Pirate Bug 2018 observation: Those flowers with Minute Pirate Bugs present had half the amount of thrips counted. Population susceptible to insecticide management of thrips/swd/lygus Bug. Populations reestablished multiple times over the season. Minute Pirate Bug, Orius spp.
Thrips Management Chemical Control Thresholds: Location dependent (Oregon = 10-15, California = 7-10) Difficult to manage so monitor this insect through season. Yellow sticky card Shaking flowers over a light colored surface Directly count population on flower with handlens Choose pesticides that are most insect specific/least toxic Contact Insecticides (Pyrethrins, spinosads, etc)
Lygus Bug Adults: Small (5-6mm), brown/pale green colored with yellow/black/tan triangle marking. Overwinter as adult in leaf detritus Adults and Nymphs feed on buds, bloom and small fruit Misshapen fruit or cat-faced fruit Typically three generations per year (June Sept) Nymphs are fast moving, green colored insects. Multiple host plant species and population moves into neighboring hosts quickly Lygus Bug Nymph
Lygus Management Biological/Cultural Beneficial Insects: Parasitoid wasps, damsel bugs, minute pirate bugs or spiders Refrain from alternate hosts around field: Clover, bean, vetch Vacuuming Lygus off plants
Lygus Bug Chemical Control Thresholds: Usually the first sight of adults or one nymph/adults per 20 plants. Difficult to manage so scout through the season. Monitor initial nymph population to gauge when adults appear Sweep netting Count nymphs/adults as soon as plant area is disturb Follow degree day models in very early season Pesticides most effective on young nymph stage Contact Insecticides (Bifenthrin, Malathion, etc) IGR like Rimon is helpful in early season to manage the initial nymph population.
Spotted Wing Drosophila Adults: Small (2-3mm) vinegar fly attracted to ripening fruit. Males have black spot on edge of wing Females lay several hundred eggs in ripening fruit by puncturing fruit with saw-like ovipositor over 3-4 week lifetime Larvae feed for 5-7 days before pupating. Several generations per year (April-November) Overwinter as adults Populations move to neighboring fruiting hosts Photos by Wendy Hoashi-Erhardt
SWD Cultural Factors Lower Risk Following hard winter freezes Before mid-july Temperatures above 80F Dry, low humidity Fruit exposed to daily sun Higher Risk After mild winter After mid-july Peak temperatures below 80F Wet, high humidity Fruit under shade/hoop houses
SWD Chemical Control Risk varies year to year Trap adults through the season (wine-vinegar) Use salt solution to sample fruit for larvae through entire harvest season Many generations so the later the season, the more generations = lower management threshold Bifenthrin, Malathion, spinosads/spinetoram, etc. Rely on routine fruit sampling to determine management effectiveness Male SWD
Twospotted Spider Mite Eight legged 2-3mm adults with characteristic spots Overwinter as adults Populations explode in ideal conditions (dusty, hot, dry) Found on underside of leaves within webbing.
Twospotted Spider Mite- Cultural/Biological Early season, young plantings = more susceptible Flare ups attributed to management of other insect pests Follow predator mite populations in addition to twospotted. Release of purchased predator mite or Lady beetle populations in early season. Predatory Mite, Amblysieus fallacis
Two-Spotted Spider Mite- Chemical Inspect oldest leaves for eggs, adults with handlens Threshold dependent on: Ratio of mites to predators Adult vs. egg counts Weather conditions, harvest completion dates, secondary pest outbreak Several miticides are labeled for use Determine the management (egg vs. adult)
Fresh Market Newsletter See Fresh Market Newsletter for quarterly updates on strawberry related projects. Sign up for the newsletter julie@peerbolt.com https://tinyurl.com/y7g6grpe Thanks to the WSDA Specialty Crop Block Grant