brassica insects & diseases; gardening guidebook for hampshire county, massachusetts
TRANSCRIPT
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
0
0.1
0.2
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0.6
no entrust entrustAve
rage
Fle
a B
eetle
Car
d C
ount
per
Pl
ant
0
0.1
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0.5
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no pyganic pyganic
Ave
rage
Fle
a B
eetle
Car
d C
ount
per
Pl
ant
0
0.1
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no kaolin kaolin
Ave
rage
Fle
a B
eetle
Car
d C
ount
per
Pl
ant
Entrust, kaolin & pyganic all significantly reduced numbers
Flea beetle defoliation on eggplant 2009 UMass Trial on Eggplant
0
0.05
0.1
0.15
0.2
0.25
no entrust entrust
Ave
rage
Fle
a B
eetle
Her
bivo
ry p
er
Plan
t
0
0.05
0.1
0.15
0.2
0.25
no pyganic pyganic
Ave
rage
Fle
a B
eetle
Her
bivo
ry p
er
Plan
t
0
0.05
0.1
0.15
0.2
0.25
0.3
no kaolin kaolin
Ave
rage
Fle
a B
eetle
Her
bivo
ry p
er
Plan
t
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