Insect Pests in Strawberries (2007)

Insect Pests in Strawberries

Celeste Welty Extension Entomologist Ohio State University September 2007 Part 1: Identiﬁcation of strawberry pests & their damage

Part 2: Monitoring & control of strawberry pests Strawberry Pest Identiﬁcation

• Primary objectives: – Identify common pests – Identify damage • Other objectives: – Know when to look – Know where to look 12 Common Strawberry Pests

• Key pests (every ﬁeld, every year) – None • Occasional pests (some ﬁelds, some years) – Fruit pests (4) – Bud pests (1) – Stem pests (1) – Leaf pests (4) – Root pests (2) Strawberry Pests

• Fruit pests – Tarnished plant bug – Eastern ﬂower thrips – Strawberry sap beetle – Slugs Tarnished plant bug

(Ontario) (Ontario) OMAFRA OMAFRA

• Causes fruit deformities: – Apical seediness (from early damage) – Hollow seeds – ‘Cat-facing’ (from later damage) Tarnished plant bug

Adult Nymph USDA , Scott Bauer

• Adults USDA – Can ﬂy – 1/4 inch long, brown with yellow marks • Immature forms are called nymphs – Cannot ﬂy – Green with some spots • Both feed by sucking plant juices Tarnished plant bug Nymphs Adult

. of Georgia Univ • Life history: – Overwinter as adults in weeds – Nymphs (5 instars) for 3 weeks – Several (2-3) generations per year • Adults most damaging in south • Nymphs most damaging in north Tarnished plant bug

• How damage occurs: – Adults feed on flower – Nymphs feed on flower & seeds of developing fruits • Kills these seeds nymph • Fleshy part of the fruit fails to enlarge • Results in “cat-faced” or “button-berry” fruit Eastern flower thrips • Damage: – Berries dull color – Berries small, seedy, fail to enlarge or ripen – Uneven maturity • Thrips feeding: – By rasping & sucking – During bloom & fruit set Feed on seeds & tissue . of Illinois – Univ between seeds – Prefer protected sites like under calyx (cap) Eastern flower thrips

. of Illinois . of Illinois Univ Univ • Small (1/16” long), yellow/brown • Active; run fast • Life history: – Do not overwinter well in North – Long-distance migration via wind from South in spring – Many generations per year Strawberry sap beetle

• Damage in ripening berries .

– Adult beetles chew holes, deep . Price, Univ

cavities, tunnels James F of Florida – Common where berries over-ripe – Common where berries touch the ground • The beetle:

. – 1/8 inch long, dark brown

– Drop to ground & run when disturbed Ohio State Univ – Hard to ﬁnd before harvest Slugs (Ontario) OMAFRA

• Damage: – Ragged holes & tunnels in berry surface – Usually in protected sites like under the calyx (cap) – Favored by moisture, thick mulch Slugs . Minn. Univ • The slugs: – Not insects! – Slimy – Feed mostly at night • Slug eggs: – Clear, round – In clusters of about 5 eggs – Laid in the fall – Easily seen under straw in spring Strawberry Pests

• Bud pests – Clipper weevil Clipper weevil

• Names of insect: (Ontario) – Strawberry clipper – Strawberry bud weevil OMAFRA • Damage: Blossom buds dry up and fall off • Damage caused by adult female weevil:

1) punctures bud with snout . 2) lays egg in bud 3) girdles ﬂower bud 4) clips stem North Carolina State Univ Clipper weevil

• Small:

– Adult 1/10 inch long Ag Canada – Larva 1/16 inch long N. Bostanian, • Overwinter as adults in fencerows, woodlots • Active in strawberry ﬁelds when ﬂower buds are emerging from the crown • Active once >60oF • One generation per year Strawberry Pests

• Stem pests

– Meadow spittlebug

. . of Wisc

Meadow spittlebug Univ

• Damage – Weaken plant by sucking sap – Nuisance pest • Problem in weedy ﬁelds • The insect – Nymphs covered with frothy spittle . of Illinois Univ

– Nymphs small, yellow-orange

– Adult brown, 1⁄4” long, like fat . of Ky leafhopper R. Bessin, Univ Strawberry Pests

• Leaf pests – Two-spotted spider mite – Cyclamen mite

– Strawberry rootworm (adult) – Potato leafhopper Two-spotted spider mite

• Symptoms (France)

– Leaves mottled, speckled, INRA bronzed – Webbing • Damage – Reduces plant vigor – Fruit yield & size decreased – Plants can die if infestation severe & uncontrolled

• Feeding

– Sap sucking . (France) . of Ky

– Adults & immatures INRA – On leaf undersides Ric Bessin, Univ Cyclamen mite

injured (Ontario)

normal OMAFRA . of Univ Florida • Damage – Leaves yellow, crinkled, stunted – Fruits stunted, distorted – Weak growth of plants – Infestations often localized Cyclamen mite

• The mite – Sap sucker (Ontario) – Tiny, microscopic OMAFRA • Oval • Shiny

• Pink or yellow/brown

– Where? . of Florida Univ • Mid-vein of unopened leaves • Under base of ﬂower buds – When? • Peak in late spring • Peak again in early fall Strawberry rootworm (adult) • Damage – Adults: Numerous small holes in the leaves due to feeding in

. May & again in August – Larvae: Plants stunted & weak due to feeding on roots North Carolina State Univ • Adult stage – Small (1/8"), shiny, brown to black beetle . of Maine Univ – Feed at night; hide during day Potato leafhopper . Ohio State Univ

• Damage: – Leaves turn yellow at edges & between veins – Leaves become curled, stunted, distorted – Weakens strawberry plants – Most noticeable in new strawberry plantings adult Potato leafhopper • Adult

– 1/8” long, green, bullet-shaped nymph

– Takes ﬂight quickly if disturbed . • Nymph – Small, light green, 1/16” long Ohio State Univ – Does not ﬂy – Moves sideways (crab-like) when disturbed • Feeding – Sap sucked by nymphs & adults – Feed mostly on underside of leaves Potato leafhopper

• When? – Variable – Pest does not over winter in Ohio, but ﬂies from South in spring – Feeding activity is most serious during late spring & early summer – Especially check new plantings – Sometimes appears on new growth after renovation Strawberry Pests

• Root pests – Root weevils – White grubs Root weevils

. Ohio State Univ • Damage by larvae – Feed on strawberry roots & crowns – Cause plants to weaken, stunt, wilt, die – Leaves turn red – Berries undersized – Infestations in patches – A pocket can expand & cause major losses the following year Root weevils

• Damage by adults – Leaf feeding:

notched edges

– Use as indicator (Ontario) OMAFRA Root weevils • Weevil larvae: – C-shaped, thick-bodied – White or pink body

. – Brown head – * No legs – * Maximum 1/4 inch Oregon State Univ • Adult

– Have snout . . – Black or brown – About 1/4 inch long Oregon State Univ Oregon State Univ Root weevils

• 3 species Strawberry Black vine – Similar in shape root weevil weevil larvae larvae – Different in size • Adult size: Black vine – Black vine weevil (1/3”) weevil – Rough strawberry weevil (1/4”)

– Strawberry root weevil (1/5”) Rough strawberry root weevil Strawberry root weevil

. Root weevils Oregon State Univ • Behavior of adult root weevils – Feed on leaves at night – Hide in crowns & under mulch during day – Flightless, but walk • Travel short distances if food available • Travel longer distances (several 100 ft) if food needed – Mass migration from infested ﬁelds Root weevils . Oregon State Univ White grubs

• Appearance: . . of Ky

– C-shaped larvae Univ – Whitish gray body with brown head – ** 3 pairs of legs – ** Large ( 0.5 to 1.5 inch long) • Larvae of several beetle species

– May beetle (= June bug)

– Japanese beetle . Minn. – Rose chafer Univ

. White grubs . of Ky Univ • Damage by larvae: – Feed on roots of strawberry plants – Weakens plants & exposes them to pathogens • Damage by adults: – Adults feed on leaves in late summer • Behavior: – Adult females lay eggs in soil in late spring in grassy areas Part 2: Monitoring & control of strawberry pests Strawberry Pest Monitoring & Control

• Primary objective: – How to monitor each pest • Other objectives: – Threshold for each pest – Practices that prevent pests – Practices that control pests Monitoring Tools & Techniques

• Scouting – Overview scouting – Close-up scouting • Shake sampling • Sweep net sampling Overview scouting: Pests all season

• Cyclamen mite • Root weevils • White grubs Cyclamen mite

(Ontario) OMAFRA • Monitor: – Look across ﬁeld for areas with stunted plants – Check newest unfolding leaves of any stunted plants • Control – Prevent: buy uninfested plants from nursery – Apply Endosulfan (Thiodan) • High rate 1-2 days before bloom & low rate 10-14 days later • Apply in lots of water to drench crowns

. Root weevils Oregon State Univ

• Monitoring – Examine plants in areas with poor vigor – Use a spade to lift a section of row – Examine roots & surrounding soil – If weevil grubs found, then control after harvest when the adults emerge

– Examine field for leaf notching damage on leaf edges to identify time of adult (Ontario) emergence OMAFRA . Root weevils Ohio State Univ • Mechanical control – Disc infested fields • Cultural control – Crop rotation • Isolate new fields • Several 100 feet away – Trap crop • Leave 1-2 rows at edge of infested planting

. – Adults intercepted in trap rows – Adults lay eggs where unimportant

• Turn under trap rows at end of season Oregon State Univ • Do not spray the trap rows (can repel weevils)

Root weevils .

• Chemical control: Oregon State Univ – Target adult weevils with Brigade 10WP (bifenthrin) – Apply at adult peak feeding (usually July) – Apply at night when weevils active – Use the highest rate – Beware, can ﬂare spider mites – Soil fumigation destroys overwintering larvae – Some States (like Ohio) have a Special Local Needs label (24c) for use of Furadan 4F for post-harvest control of root weevil larvae

White grubs . . of Ky Univ • Cultural control: – Do not plant strawberries into a field that was grass the year before, or near to a grassy field – Prepare the field by leaving it fallow or planting it with a non-grass cover crop or alternative crop for at least one season prior to strawberries

. White Grubs . of Ky Univ • Chemical control – Spraying for adult control not very effective – Lorsban 4E • Apply before planting, incorporate – Admire 2F or Admire Pro • Post-harvest • Apply in advance of the start of egg-laying • After eggs hatch in soil, young grubs killed as they start to feed on roots • Requires rain or irrigation soon after application • Apply by normal ground equipment, banded over row, or chemigate Clipper weevil .

• Monitoring

– Early detection is important North Carolina State Univ – Sample as soon as flower buds start coming out of the crown & temp. > 65oF – Examine 1 meter (3-ft) length of row at five locations in a field • Look for clipped primary buds • Look for clipped 2o and 3o buds – Sample more from edge near woods Clipper weevil

• Many varieties can compensate for injury – if it occurs early – if only secondary or tertiary ﬂower buds are affected Strawberry Flower Order

tertiary secondary Number of Berries: • One primary • Two secondary tertiary • Four tertiary

Ag. Experiment Station primary tertiary ork State Y tertiary New secondary Clipper weevil

• Threshold: Treat if the number of clipped buds per meter of row is

• 3 or more primary buds or Ag. Experiment Station

30 or more secondary or secondary ork State

• Y

primary tertiary buds tertiary New

Clipper weevil N. Bostanian, Ag Canada

• Chemical control – Infestations begin at ﬁeld edge, so border spray is often sufﬁcient – Options: Lorsban 4EC, Brigade, Danitol USDA ,

S. Bauer Tarnished plant bug

• Monitoring 1. Sweep net for adult bugs . • Early, when buds forming

• Individual sweeps: N. Carolina State Univ – ﬁrm pendulum-like motions (handle up, net down) – through upper middle canopy – while walking down row

• Treat if >2 adult bugs per 10 sweeps . of Kentucky Univ

USDA Tarnished plant bug

• Monitoring (Ontario)

2. Shake sampling for nymphs OMAFRA • Begin just prior to bloom • Sample once per week • Shake 30 ﬂower clusters (6 clusters in 5 different locations) over shallow pan • Threshold: – Treat if 4 or more of the clusters out of the 30 sampled have any nymphs – OR Treat if > 0.25 nymph per cluster, if before 10% bloom – & Treat if > 0.5 nymph per cluster, if during mid- to late bloom

KSU

Tarnished plant bug

• Cultural control dandelion – Control weeds • Weeds are also host plants • Especially weeds that ﬂower before strawberries bloom • Do not to disturb (pull, mow) the chickweed weeds while strawberries are in

susceptible stage

– Avoid planting within 500 meters . of Missouri of alfalfa or weedy ditch or Univ fencerow pigweed

USDA Tarnished plant bug • Cultural control – Variety selection • ‘Honeoye’ typically has less damage than ‘Earliglow’ • Varieties that produce more flowers and fruit per area suffer less fruit damage than less productive plants • Varieties that flower earlier have less severe damage than later-flowering varieties

USDA Tarnished plant bug • Mechanical control – Row covers • Chemical control – Difficult • Adults tolerant of insecticides • Very mobile, recolonize quickly – Timing • If above threshold • After blossom buds first visible • Again just before bloom – Products: • Endosulfan (= Thiodan) is the standard • Other options: Brigade, Danitol, Malathion, PyGanic Eastern flower thrips . of Illinois Univ • Monitoring – Tap 5 to 10 blossoms onto white pan or cup OR Place 5 to 10 blossoms in zip-top bag, shake – Sample 5 to 10 areas within a planting – In each area, pick 5 to 10 blossoms – Count the thrips in pan or bag – Calculate average number of thrips / blossom – Begin when first blossoms open – Repeat weekly until all berries reach diameter of a dime Eastern flower thrips

• Threshold – Counts in many plantings will be less than 1 thrips per ﬂower, and control will not be needed – Treat if > 2 to 10 thrips per ﬂower

. of Illinois Univ Eastern flower thrips . of Illinois Univ • Chemical control – Conventional growers • Lorsban applied very early (21-day PHI) • Brigade • Danitol – Organic growers • Entrust (spinosad) • neem (Neemix & others) Meadow spittlebug . of Wisc. Univ • Monitoring – Start to scout when plants ~10% bloom – Randomly choose 5 one-square-foot areas per field every week – Spread leaves and inspect crowns, leaf bases, leaf stems, flower stems looking for white, frothy spittle masses • Threshold: Treat if average number of spittle masses is > two per square foot • Insecticides: Endosulfan (Thiodan), Brigade, Danitol Two-spotted spider mite

. • Monitoring Early detection is critical

– Ric Bessin, Univ of Ky – Collect 60 leaves – Use hand lens to examine undersides for presence of mites • Threshold (from New England): – More than 15 of 60 leaves have mites (>25%) – Double the threshold if predators present (>50%) Two-spotted spider mite

. • Cultural control – Renovation Ric Bessin, Univ of Ky • Biological control – Conserve natural enemies – Buy & release predatory mites • Chemical control – Need good coverage – Agri-Mek, Savey, Zeal, Oberon, Acramite, Kanemite Potato leafhopper

• Monitor by scouting – Brush leaves with hand and adult look for small adults ﬂying off

– Examine underside of nymph

injured leaves to see if . nymphs present Ohio State Univ

Potato leafhopper . Ohio State Univ • Control – Insecticides should be applied only when large populations of nymphs are found – Sevin (carbaryl) registered for use – (or Brigade or Danitol work, but this pest not on label) Strawberry rootworm (adult)

• Monitoring . . of Maine – Look for small holes in leaf Univ – Scout after dark by ﬂashlight N. Carolina State Univ – 10-20 beetles per square foot is high • Control – Should be considered if feeding injury increasing, & beetles present – No product registered for this pest – Sevin, Brigade, Endosulfan (Thiodan) used for other pests will also control rootworm adults

Strawberry sap beetle .

. Price, Univ

• Cultural controls: James F of Florida – ** Sanitation & timely harvest **

. – Remove damaged or over-ripe berries – Picking plants thoroughly & regularly Ohio State Univ • Mechanical – Trap buckets of over-ripe fruit at ﬁeld edge • Chemical – Difﬁcult because beetles protected inside berry – Insecticide with short restrictions: Brigade – Beware: spraying during harvest can be unsettling for customers

Slug Control . Minn. Univ

• Cultural – Lower plant density – Delay fall mulching – Remove debris around ﬁeld • Mechanical – Board traps • Chemical baits Slug Control (Ontario) OMAFRA • Chemical baits – Best if applied to moist soil – If dry, can irrigate just before applying bait, to stimulate slug activity – Avoid watering for 3-4 days after application – Ideal to apply in late afternoon or evening Slug Control • Chemical baits – Metaldehyde (Deadline MPs) • Blue mini-pellets • Kill slugs by over-stimulating mucous • Prevents damage • Toxic to dogs • Works best when temperature warm – Iron phosphate (Sluggo) • Light brown; less visible to pickers • Safe to humans, animals, natural enemies • Less rapid toxic effect • Stop the slugs from feeding

• Eventually leads to their death . Minn. Univ Summary of Strawberry Pest Management Monitoring & Control Tactics Monitoring June-bearing strawberry crops

Time Method Target Pest All season Overview field Cyclamen mite (March to scouting, every 2 Root weevil August) weeks White grubs When buds are Early-season bud Clipper weevil forming (April) scouting, weekly When buds are Sweep net sampling, Tarnished plant bug adults forming (April) weekly Starting at first Shake sampling, Tarnished plant bug nymphs bloom (May) weekly Thrips May Close-up plant Spittlebug, Spider mites, scouting, weekly Rootworm beetles, Leafhoppers May, June Close-up scouting Slugs near harvest, weekly Sap beetles July Scout for leaf notching Root weevils Strawberry Pest Management Tactics 1. Cultural controls – For new plantings • Site selection – Not after grass (white grubs) – Not near root weevil infested field • Trap crop (root weevil) • Variety selection (plant bug) • Clean nursery stock (cyclamen mite) – In established plantings • Weed control (plant bug & spittlebug) • Prompt harvest (sap beetles) • Delay mulching (slugs) Strawberry Pest Management Tactics

2. Mechanical controls – Disc under root weevil infestation – Bait buckets (sap beetles) – Row covers (tarnished plant bug) 3. Biological controls – Conserve natural enemies by avoiding insecticide use – Parasitoid of sap beetles – Predatory mites for spider mite Strawberry Pest Management Tactics

4. Chemical control options – Spray insecticide on plant foliage • Mostly for tarnished plant bug • Spot treatment for clipper weevil • Occasional for spittlebug, sap beetle, leafhopper, rootworm beetle – Spray miticide on plant foliage – Apply insecticide to soil • White grubs – Apply slug bait around plants The End