Brassica insects and diseases

Ruth Hazzard New England Vegetable and Fruit

Conference 2013

Brassicas – a diverse crop group Brassica oleraceae Brassica rapa

Brassica napa Brassica juncea

Bok Choy.

Turnip

Kale,

“head

& stem”

Mustard

Red Russian

Kale, Rutabaga

Raphanus sativus, radish Eruca sativa, arugula

Chronological order, more or less Focus on farm-wide strategies, troublesome pests or

‘something new’ Insects • Flea beetle • Cabbage root maggot • Imported cabbageworm • Diamondback moth • Cross-striped cabbageworm • Swede midge • Cabbage looper • Onion thrips • Cabbage aphid

Diseases Black rot of Brassicas Alternaria leaf spot Downy mildew of Brassicas Club root

Crop rotation goals: avoid building up pest & disease

1. 3 years out of Brassicas • Is the proportion of cropped

acreage in Brassicas too high?

• Are fields separated? • Is crop residue tilled?

2. Separate fall and spring crops What moves in-season? flea beetle cabbage root maggot thrips Alternaria black rot caterpillars Swede midge ADD OVERVIEW OF FARM FIELDS

Crop rotation goals: reduce, escape insects & diseases

Overwintering locations for disease: crop residue in or on soil, weeds

Crop rotation goals: reduce, escape insects & diseases

Overwintering locations for insects: field edges, crop residue, alternate hosts

Overwintering locations for disease: crop residue in or on soil, weeds

Crop rotation goals: reduce, escape insects & diseases

Overwintering locations for insects: field edges, crop residue, alternate hosts

Overwintering locations for disease: crop residue in or on soil, weeds

Spring? Fall? Next Spring?

General Cultural Practices

Crop rotation Incorporate crop residue Adequate crop spacing Drip Irrigation Adequate nutrition Scout under leaves

Pre-plant Prevention: Clean Seed

Healthy Seed • Seedborne diseases:

– Alternaria (fungal) – Black Rot (bacteria) – Downy mildew

• Possible sources: – saved seed – purchased seed

Hot Water Seed Treatment • 15-30 minutes • 122 F Needed: screen/coffee filters accurate thermometer hot water bath http://vegetablemdonline.ppath.cornell.edu/NewsArticles/HotWaterSeedTreatment.html

Cruciferous Weeds Are Everywhere!

• Four-petaled flower (white or yellow) • Narrow seed pot, round seeds • Rosette vegetative • Tall upright stem reproductive

alyssum hoary Berteroa incana bittercress Cardamine hirsuta bittercress cuckoo Cardamine pratensis cress mouse-ear Arabidopsis thaliana damesrocket Hesperis matronalis fieldcress prostrate Rorippa x prostrata mustard garlic Alliaria petiolata mustard hedge Sisymbrium officinale mustard tower Arabis glabra mustard wallflower Erysimum cheiranthoides mustard wild Brassica kaber pennycress field Thlaspi arvense pepperweed field Lepidium campestre pepperweed Virginia Lepidium virginicum radish wild Raphanus raphanistrum rocket yellow Barbarea vulgaris shepherd's-purse Capsella bursa-pastoris whitlow grass spring Draba verna yellowcress marsh

For ID see: UMass Extension Weed Herbarium – mustard family

Regular scouting -- You and the Crew! • Scout weekly, alone or with the crew • Notice things! early feeding damage,

tiny disease lesions • Respond when its not too late!

Flea beetles

• Overwinter in field edges • Find spring crops quickly and

early • Preference for B rapa, B juncea,

arugula

ADULT

Underground, near plant roots

EGGS

LARVA

PUPA

Above ground, on foliage

Flea beetle life cycle

•Overwinter as adult •Lay eggs - May •New adults emerge midsummer 2nd generation in fall

Peak adult numbers: 1. May-June 2. Late July – early August

Flea beetle Management Strategies 1. Escape them: crop rotation between and

during the season 2. Starve them: no spring Brassicas 3. Kill them: till immediately after harvest, use

insecticides 4. Exclude them: row cover 5. Use trap crops, spray those more often

Insecticides for flea beetle Synthetic

Pyrethroids: 3A • beta-cyfluthrin (Baythroid* XL) • bifenthrin (Brigade* 2EC) • cypermethrin (Ammo* 2.5EC) • lambda-cyhalothrin (Warrior* II) • permethrin (Pounce* 25WP) • esfenvalerate (Asana* XL) • gamma-cyhalothrin (Proaxis*) • zeta-cypermethrin (Mustang*) Carbamates (1A) • carbaryl (Sevin XLR Plus) Neonicotinoids: (4A) Foliar applied: • dinotefuran (Venom) • imidacloprid (Provado 1.6F) 7 dh • thiamethoxam (Actara): 0 to 7 dh Soil applied: thiamethoxam (Platinum): 30 dh/ in-furrow, banded, drench, or drip; Also seed trt. Diamide: Coragen

Organic (OMRI listed) • kaolin (Surround WPOG): use

on transplants, seedlings and young plants.

• pyrethrin (PyGanic EC5.0OG) • spinosad (EntrustOG) • azadiractin (Neemix 4.5)

Flea beetle numbers on sticky card traps 2009 UMass Trial on Eggplant

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Entrust, kaolin & pyganic all significantly reduced numbers

Flea beetle defoliation on eggplant 2009 UMass Trial on Eggplant

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Only kaolin had significantly less feeding damage

Mixtures seem to have an additive effect

We have seen growers use with success in eggplant:

--Surround alone --Surround mixed with

Entrust

Row cover also works great for early season control!

Trap cropping for flea beetle • Keep it simple • B rapa, B juncea/mix

– Komatsuna, mustard – cheap seed

• Borders OR In-field strips • Main crop: less preferred

– B oleracea, B. napa. • Scout weekly • Spray --‘Concentrate &

kill’

Full Bloom Farm trap crop study, 2013

bok choykale 2lacinato 2red russian 2border mixkalelacinatored russianborder mixroad

last year's brassicas

+ successions of bok choy

Full Bloom Farm trap crop study, 2013

• Trap crops: • Brassica rapa, B. juncea border mix DS • ‘Sink’ crop (bok choy, napa) (2-4 A) • Main crop: kale, collard, lacinato, red

Russian (8 A) • Thresholds: 1 to 2/plant, 10-25%

damage – call for sprays • Products: Pyganic 16 oz, Entrust 2 oz

– Nufilm • Results (FB sprays) : 7 sprays on bok

choy, 1 spray on kales (June1 to Aug1) • Product strategy: Pyganic for knockdown

(rain coming), Entrust for residual, mix if pressure is high

bok choykale 2lacinato 2red russian 2border mixkalelacinatored russianborder mixroad

last year's brassicas

+ successions of bok choy

Imported cabbageworm and diamondback moth

• Multiple generations • Scout under leaves, use threshold

(35-50% early, 15-20% at heading, for leafy greens)

• Use selective insecticides to protect natural enemies

active and wiggly !

Fuzzy & sluggish!

DAY

NIGHT

Cotesia rubecula, Braconid wasp parasite of imported cabbageworm

• Released 1988 by Roy Van Driesche in MA • 2011 survey: spread throughout Northeast

and Central US, high levels of parasitism • Attacks second instars • Kills caterpillars before feeding damage • Look for cocoons

White larva inside ICW caterpillar

Range is moving northward

Established in Connecticut & MA

Eggs laid in cluster

Caterpillars feed in a group and destroy single plants

Controlled by same products as other caterpillars

Moth and group larvae photos by Dr L. T. Kok Virginia Tech, Blacksburg, VA

Cross-striped cabbageworm

(Evergestis rimosalis

Black Rot of Brassicas, Xanthomonas campestris pv. campestris

• Species is specific to Brassicas

• Bacterial • Plugs waterconducting

tissue with xantham, mucilagenous sugar

Sources: • Seed (0.3% of one seed lot can infect the

field) • infected crops & weeds • Crop residue (overwinter) esp. tough stems • Survives in soil 40-60 days • Spread in the field by rain, wind,

equipment, people, insects • Enters through wounds and hydathodes

Conditions: warm moist (80-86 F optimum)

https://www.apsnet.org/edcenter/illglossary/ Photo credit: Holly Lange, Cornell U

Black Rot of Brassicas, Xanthomonas campestris pv. campestris Bacterial Plugs watercnduting tissue with xantham, mucilagenous sugar

Symptoms • V-shaped yellow lesion from leaf

marging toward center of leaf NOTE black veins

• Mid-leaf dark patches between veins • Petiole, stem • Roots – affects turnip & rutagabag • Followed by soft rot (smelly)

Black Rot of Brassicas, Xanthomonas campestris pv. campestris

• Spray at 7-10 day intervals

• Preventatively • At first detection • When conditions

are favorable

Chemical control Copper products • Kocide (not OG)

• Organic: eg Badge X2 OG

Synthetic • Copper + mancozeb: eg Mankocide

• Tanos

Plant defense activators • Actigard 50 WG (Acibenzolar-S-methyl)

• Regalia BiofungicideOG (Reynoutria sachaliensis Extract)

Alternaria leaf spot (A. brassicae, A. brassicicola

Species specific to Brassicas Sources: • Infected seed • Crop residue (overwinter) esp

tough stems • Infected crops & weeds • Sporulates on infected residue • Moved around by rain splash,

wind, equipment, people, insects

Conditions: cool, moist (60-78 F optimum) • advances in late summer & fall • Develops in the canopy – long

leaf wetness periods

Alternaria leaf spot

Symptoms

Alternaria starts on lower leaves & inside canopy, where leaf wetness is greatest

Chemical control Synthetic • Quadris (11), Quadris Top (11),

Endura (7), Bravo Weather Stik(M5) • Switch (9&12), Inspire (3), Inspire

Super (3 & 9), Aproach (11), Rovral (2), Cabrio

Organic/biofungicide • Double Nickel Bacillus

amyloliquefaciens • Has shown efficacy in two trials

Alternaria leaf spot

Alternaria and Black Rot on Collard 2013 UMass Trial, Sue Scheufele

Treatment and Rate (/A)x

ALS Severityy

(%)BR Severityz

(%)Untreated Control………………… 1.4 ab 3.1 bQuadris, 15 fl oz…………………… 0.1 a 1.8 abActigard 50WG, 1 oz……………… 2.0 ab 1.5 abSerenade Optimum, 20 oz………… 1.0 ab 2.3 abSonata, 4 qt………………………… 1.0 ab 1.6 abDouble Nickel 55, 6 qt…………… 0.5 a 0.6 aActinovate AG, 12 oz……………… 2.3 ab 1.5 abBadge X2 DF, 0.75 lb……………… 2.5 ab 0.6 aBasic Copper 53, 3 lb……………… 4.8 b 1.6 abTaegro, 5.2 oz……………………… 1.0 ab 1.4 abp-value 0.0233 0.0472

• Reduces vigor, growth, & marketability; opens wounds

• Moves from mature onions into late Brassicas

• Varietal resistance: http://veg-guidelines.cce.cornell.edu/15frameset.html; www.nevegetable.org

Onion thrips (Thrips tabaci)

• Other hosts: Aliums, alfalfa, wheat, clover

• Rasping of epidermis becomes rough, brown scar tissue. Cabbage: scars inside head

Thrips, up close

• Organic:

• Spinosad (Entrust) controls thrips, flea beetle, and caterpillars

• Conventional:

• pyrethroids,

• nicotinoids,

• spinosyns (Radiant)

Onion thrips (Thrips tabaci)

Downy Mildew of Brassicas (Peronospora parasitica)

Species is specific to Brassicas Sources: • seed • infected living crops & weeds • resting spores (long-lived, survive winter)

Conditions: cool, moist • Rain, dew, fog, GH humidity • Spores released, germinate & infect

Symptoms • Irregular angular yellow-brown spots on

upper leaf • Greyish white fluffy growth on underside

Downy Mildew of Brassicas

Cultural Controls Resistant varieties: Broccoli (Marathon, Arcadia) Field: 2-3 yr rotation Wider crop spacing, use drip GH: clean seed, clean growing media, manage humidity and T Sanitation: Remove or destroy infected plants Control brassica weeds

More Symptoms Seedling: cotyledons speckled, yellowing Brocc., caul., cabbage: infection of head

Dark brown areas on surface Internal dark or purple streaks

Downy Mildew of Brassicas Spray preventatively or at first detection Confirm ID with diagnostic lab

Synthetic fungicides • oomycete specific

– Revus (40) – Forum (40) – Presidio – Reason SC (11) – Zampro (40 & 5)

Broad-spectrum – chlorothalonil (Bravo Weather Stik) – Ridomil (4) – Ridomil Gold (4 & M5)

Organic – Copper products

Swede Midge • Scout, learn symptoms, contact Extension if you see it.

http://web.entomology.cornell.edu/shelton/swede-midge/index.html

Source: Christy Heopting, Cornell U

Swede midge: larvae

0.3 to 3-4 mm

Source: Christy Heopting, Cornell U

Many types of damage

Source: Christy Heopting, Cornell U

Cabbage Looper

Migratory – late summer Scout as for other caterpillars Larger, ragged feeding holes If you see it in Brassicas, also scout spinach, chard, lettuce