Management of downy mildew, onion neck rot and maggot damage on onions 2014

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1 Management of downy mildew, onion neck rot and maggot damage on onions 2014 Mary Ruth McDonald Laura Riches, Kevin Vander Kooi, Alan Taylor Dept. of Plant Agriculture, Univ. of Guelph Cornel University

2 Holland Marsh, Ontario, Canada 44 o 15 N, 79 o 35 W Tulare, California 36.2 o N o W

3 Onion downy mildew

4 Onion downy mildew (Peronospora destructor) Caused by a water mold, not a true fungus Attacks only onion and related crops, such as chives Starts in hot spots Grows systemically in the plant, no symptoms until it sporulates 3 or 4 cycles can destroy a crop

night Humidity above 95% at night, No rain after 1:00 am Infection occurs in

5 NO symptoms until sporulation occurs Onion downy mildew Sporulates when temperatures below 75 o F, (24 o C) previous day Temp o F (4 24 o C) at night Humidity above 95% at night, No rain after 1:00 am Infection occurs in 3-6 hours, temp o F (4-26 C) Takes 10 to 12 days from infection until sporulation

6 Fungicides registered for downy mildew on onions- UC Davis web site Reason (fenamidone) Ridomil Gold (mefanoxam/mancozeb) Ridomil Gold/ Bravo (mefanoxam/chlorothalonil) Chlorothalonil (Bravo etc.) Mancozeb (Pencozeb, Dithane and other products) Maneb Copper (NuCop and other coppers)

7 Fungicides for downy mildew of onion Treatment Rate/ha Lesions per leaf 14 August RIDOMIL mefanoxam 2.5 kg 0.0 a 2 PRESIDIO + DITHANE fluopicolide 292 ml+3.25 kg 0.2 a DITHANE maneb 3.25 kg 0.1 a RANMAN cyzofamid 200 ml 0.8 abc REVUS + non-ionic adjuvant mandipropamid 600 ml % v/v 0.4 ab RIDOMIL alternated mefanoxam + with ALIETTE fosetyl-al 2.5 kg or 2.8 kg 0.6 abc Check de REASON fenamidone 400 ml 1.2 bcd CABRIO azoxystrobin 840 g 1.5 cd PRESIDIO fluopicolide 292 ml 1.7 d PRESIDIO fluopicolide 146 ml 0.7 abc ALIETTE fosetly-al 2.8 kg 2.6 e

8 Fungicide treatments for downy mildew control Treatment ZAMPRO (ametoctradin+dimethomorph) OXTP (oxathiapipronil formerly QGU42) DITHANE (macozeb 75%) Rate (per ha) 1.0 L % v/v Sylgard 350 ml 32.5 kg QUADRIS TOP (azoxystrobin+difenoconazole) 1.0 L RIDOMIL/ALIETTE 2 (mefanoxam/ fosetyl-al OMEGA (Allegro, fluazinam 50%) CABRIO (pyraclostrbin 20%) 2.5/2.8 kg 1.16 L 840 g Check

9 Fungicides for control of onion downy mildew: 2014 Lesions per leaf 3 No significant differences

10 Onion downy mildew Downy mildew develops first in small hot spots- not evenly distributed Fungicides must be applied before infection takes place, but with correct timing, even maneb can reduce disease Warm temperatures and dry weather halt disease development Fungicides Zampro +adjuvant and OXTP look very promising for downy mildew control

sporulate on the dying cotyledon, and infect other leaves.

11 Onion neck rot (Botrytis allii, B. aclada, B. byssoidea) Can be on onion seed The cotyledon becomes infected from the seed coat, fungus can sporulate on the dying cotyledon, and infect other leaves. Spores land on leaves during the growing season Infection takes place during cool, (50-68 o F) humid weather Latent infection. Usually no symptoms until onions are in storage

12 Onion neck rot Infection can also occur at harvest if the necks have some green or moist tissue Does not spread from bulb to bulb in storage, but can become worse the longer the bulbs are stored. Some late maturing red onions are very susceptible, as are white onions.

Evaluation of fungicides for the control of onion neck rot -2013 Percent

13 Evaluation of fungicides for the control of onion neck rot Percent bulbs with symptoms * Yellow bulb onions cv. Pontiac 5 0

14 Onion neck rot-objectives To evaluate fungicides for the control of onion neck rot To evaluate the timing of fungicide applications to optimize the control of neck rot White dehydrator onion

15 Fungicides for neck rot control-2014 TTreatment Activeingredient Rate L/ha Fontelis penthiopyrad 1.75 Pristine boscalid + pyraclostrobin 1.3 Luna Tranquility fluopyram+pyrimethanil 1.2 Omega fluzainam 1.16 Switch cyprodinil+fludioxonil 975 g Quadris Top azoxstrobin + difenoconzole Scala pyrimethanil 2.0 Check 1.0

intervals) Onions pulled Sept 29 (late harvest) not subjected

16 Onion neck rot: Methods Seeded 14 May Fungicides sprays began 16 July 5 sprays (July 16, 24, Aug 6,15, 26 (~ 10 day intervals) Onions pulled Sept 29 (late harvest) not subjected to artificial curing Assessed 21 Jan. Bulbs were cut and examined for symptoms

17 Evaluation of fungicides for the control of onion neck rot: dehydrator onion 2014 Percent bulbs with symptoms c bc bc bc bc abc ab a

18 Fungicide spray timing for control of neck rot Disease forecasting systems were tested First true leaf (to prevent infection from cotyledon (1) Botcast developed for Botrytis leaf blight (4) (combination of temp. and leaf wetness) Tomcast with Disease Severity Values of 20 and 30 (combination of temp. and leaf wetness) (8,7) 6 th true leaf (6) 2 nd week of August (before lodging) (3) Just before lodging (1) Unsprayed (0)

19 Fungicide application timing for control of onion neck rot st Application: 12 Jun 30 Jun 8 Jul 15 Jul 24 Jul 5 Ag 12 Ag 25 Ag 3 Sep Total # App s 1 st true leaf X BOTCAST X X X X leaf stage X X X X X X 6 20 DSV X -- X X X X X X X TOMCAST 8 30 DSV X X X X X X X TOMCAST 7 2 nd week of X X X August 3 just before X lodging 1 check Dehydrator (white) onion seeded 13 May

20 Evaluation of spray timing with Quadris Top for the control of onion neck rot: dehydrator onion 2014 Percent bulbs with symptoms Check One true leaf Before lodging 2nd week Aug Botcast 30 6 leaf stage Tomcast 30 Tomcast 20

21 Fungicides and spray timing for the control of onion neck rot- Conclusions White onions are very susceptible High disease pressure in 2014 Fontelis and Pristine were most effective(5 sprays, starting July 16) but none of the products provided commercially aceptable control. Next steps: continue fungicide trials (reduce disease pressure) Spray timing variations: first spray at one true leaf, followed by different timings

22 Onion maggots and seed corn maggots- up to 70 to 100% loss, most years

23 Onion maggot and Seed Corn Maggot. 3:1 onion maggot to seed corn maggot Onion maggot fly Seed corn maggot fly

24 Insecticide treatments on Pulsar Treatment Active ingredient Rate Capture bifluthrin 0.38 g/m Force tefluthrin 0.46 ml/m Lorsban 15% chlorpyrifos 32 kg/ha Movento + Sylgard 24% spriotetromat + syloxilated polyether 76% Avicta % abamectin 4.55 Entrust 80% spinosad ml % Entrust +Cruiser 80% spinosad+70% thiamthoxam Sepresto 56.25% clothianidin % 5.45 imidicloprid Trigard 75% cyromazine 5.0 Untreated

25 First generation maggot damage Percent damage In-furrow

26 Insecticide treatments Treatment Active ingredient Rate Verimark cyantraniliprole 1 L/ha Actara thiamethoxam 4.4 ml/100m Capture bifluthrin 3 ml/100m Force tefluthrin 37.5 g/100m Lorsban 15% chlorpyrifos 32 kg/ha Entrust 80% spinosad 0.2 mgai/s Entrust +Cruiser 80% spinosad+70% thiamthoxam 0.2 mgai/s Sepresto 56.25% clothianidin % imidicloprid 0.2 mgai/s Trigard 75% cyromazine 0.05 mgai/s Untreated

Effect of maggot treatments on total season maggot damage - 2014

27 Effect of maggot treatments on total season maggot damage Percent onions damaged 60 In-furrow cd d cd bc bc abc ab a a a 0

28 Effect of maggot treatments on total season maggot damage Yield (tonnes/ha) 120 In-furrow bc de cde e abc ab ab a bcd ab

Conclusions: Maggot control Seed treatments Entrust, Entrust plus Cruiser (FarMore Fl 500), Sepresto, and Trigard all effectively reduced maggot damage.

29 Conclusions: Maggot control Seed treatments Entrust, Entrust plus Cruiser (FarMore Fl 500), Sepresto, and Trigard all effectively reduced maggot damage. In-furrow applications were not as effective as seed treatments in 2014 Verimark looked the most promising High rainfall (3.5 in) in June may have leached the products away from the plant?

30 Overall Conclusions Downy mildew: Zampro and OXTP appear to be the most promising fungicides Neck rot: White onions are highly susceptible. Fungicides Fontelis and Pristine are most effective Maggots: in-furrow treatments were not as effective as seed treatments not effective under high rainfall or irrigation? Seed treatments Sepresto, Trigard, Entrust and Entrust plus Cruiser are highly effective

31 All research trials are summarized in the Annual Report Download at the Muck Station web site: report will be available by the end of March

33 / Questions?

Seed treatments for control of onion and seed corn maggots. Mary Ruth McDonald Dennis VanDyk, Alan G. Taylor

Seed treatments for control of onion and seed corn maggots. Mary Ruth McDonald Dennis VanDyk, Alan G. Taylor Long day yellow bulb onions Most grown on muck soil with 45-70 % organic matter. Seeded late