Flea Beetle Feeding and Tomato Early Blight

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

I visited a few tomato fields this week and found 2 to 4-week-old tomato plants with some early blight (Alternaria solani) and in some cases bad early blight lesions. This is very early in the season to be seeing this level of early blight. Many of the plants had a few flea beetle adults on the plant (Fig. 1) and in the areas where the early blight was found also had moderate to high flea beetle feeding (Fig. 2). In some cases I could not find any flea beetles after the rains we have had and in other cases I could find a few of them. Normally the amount of flea beetle feeding I saw would not have been of much concern, but flea beetles can cause increased infections of Alternaria leaf blight in tomatoes and potatoes and possibly other early blight susceptible crops. I found that there was a strong relationship between the amount of flea beetle feeding and the amount of early blight on tomato plants in different fields of a few farms. If you have moderate flea beetle feeding damage to your Solanaceae plants and you see any early blight starting you’ll need to control both the beetle and the disease. Pyrethroids should work well in controlling flea beetles. There is not much organically that will control flea beetles once they are causing economic damage (there are some things that can be done though, to reduce flea beetle problems before flea beetles cause damage, more at: https://attra.ncat.org/attra-pub/download.php?id=135). Using kaolin clay (Surround) before beetles begin to feed on plants is one organic possibility as is using spinosad on beetles after they start to feed.

Flea beetle adults are generally small and range in size from 0.05 to 0.15 inch. They overwinter as adults on weed hosts surrounding the field, on residues of a previous tomato crop, or in the soil if the previous crop was a flea beetle host. Some flea beetles (Systena blanda – the pale striped flea beetle being one) can feed on amaranths or pigweeds (Fig. 3) and will readily move from them over to your crops. Other flea beetles are more host specific (the eggplant, potato and tobacco flea beetles feed on Solanaceous plants while others prefer broccoli, cabbage and other cole crops). However all adult flea beetles have similar damage patterns, they chew small round holes in leaves, which make them look as if they have been damaged by fine buckshot, called “shot-holing”. The white larvae feed on underground parts of the plant, but this damage is usually not economically significant. There is normally a second generation during the summer and at times even a third depending on species. Normally foliar damage to larger plants is not considered to be economically important but feeding damage to small plants or seedlings can reduce stand or vigor of the plant. The other exception about flea beetles not being economic pests is when Alternaria is associated with their feeding on smaller tomato plants.

Figure 1. Underside of tomato leaflet with two flea beetles (Epitrix sp)

Figure 2. Tomato leaf with old flea beetle feeding and early blight

Figure 3. Pale striped flea beetle feeding on amaranthus weed

Potato Disease Advisory #2 – May 23, 2014

Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu

Date DSV Total DSV Accumulated P-Days Spray Interval Recommendation
5/12-5/21 19 19 81 5-days
5/21-5/23 2 21 100 10-days

Location: Leipsic, Kent Count, Delaware

Green row: May 12, 2013

Late Blight
The threshold of 18 DSVs has been exceeded. Protective fungicides are recommended. Twenty-one (21) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 12.

Any suspect samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local extension office. See the 2014 Commercial Vegetable Production Recommendations-Delaware for recommended fungicides: http://extension.udel.edu/ag/vegetable-fruit-resources/commercial-vegetable-production-recommendations/

The website USABlight tracks tomato and potato late blight across the nation and can be found here: http://usablight.org/. Information on scouting, symptomology, and management can also be found on this website.

Early Blight
One-hundred (100) P-days have accumulated. No fungicides for early blight control are recommended. Commercial fungicide recommendations can be found in the 2014 Commercial Vegetable Production Recommendations-Delaware: http://extension.udel.edu/ag/vegetable-fruit-resources/commercial-vegetable-production-recommendations/

Potato Disease Advisory #12 – July 19, 2013

Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu and Phillip Sylvester, Kent Co. Ag Agent; phillip@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County
Greenrow: May 5

Date

DSV

Total DSV

Accumulated

P-Days

Spray Interval Recommendation

5/23 – 5/27

5

39

5-days

5/27 – 5/30

0

39

10-days

5/30 – 6/6

2

41

251

10-days

6/6 – 6/7

10

51

261

5-days

6/7 – 6/9

10

61

280

5-days

6/9 – 6-13

4

65

314

7-days

6/16 – 6/20

13

78

377

7-days

6/20 – 6/27

6

84

420

7-days

6/28 – 7/4

24

108

477

5-days

7/5 – 7/11

4

112

516

10-days

7/12 – 7/18

11

125

552

10-days

Late Blight
The threshold of 18 DSVs has been exceeded. One hundred and twenty five (125) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. Growers should continue to scout their potato fields and consider applying fungicides preventatively. Any suspect samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local extension office. See the 2013 Commercial Vegetable Production Recommendations-Delaware for recommended fungicides: http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf. The website USABlight tracks tomato and potato late blight across the nation and can be found here: http://usablight.org/. Information on scouting, symptomology, and management can also be found on this website.

Early Blight
The threshold of 300 P-Days has been exceeded. Five hundred and fifty-two (552) P-days have accumulated. A fungicide for early blight control is recommended. Commercial fungicide recommendations can be found in the 2013 Delaware Commercial Vegetable Recommendations Guide at http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Potato Disease Advisory #10 – July 5, 2013

Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu and Phillip Sylvester, Kent Co. Ag Agent; phillip@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County
Greenrow: May 5

Date

DSV

Total DSV

Accumulated

P-Days

Spray Interval Recommendation

5/15 – 5/20

11

32

5-days

5/20 – 5/23

2

34

5-days

5/23 – 5/27

5

39

5-days

5/27 – 5/30

0

39

10-days

5/30 – 6/6

2

41

251

10-days

6/6 – 6/7

10

51

261

5-days

6/7 – 6/9

10

61

280

5-days

6/9 – 6-13

4

65

314

7-days

6/16 – 6/20

13

78

377

7-days

6/20 – 6/27

6

84

420

7-days

6/28 – 7/4

24

108

477

5-days

 

Late Blight
The threshold of 18 DSVs has been exceeded. One hundred and eight (108) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. Late blight was reported on a commercial potato field near Leipsic, Delaware as of July 2, 2013. Growers should aggressively scout their potato fields and apply preventative sprays at a 5-day spray interval. Any suspicious samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local Extension office. See the 2013 Commercial Vegetable Production Recommendations-Delaware: http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf.The website USABlight tracks tomato and potato late blight across the nation and can be found here: http://usablight.org/

Early Blight
The threshold of 300 P-Days has been exceeded. Four hundred and seventy seven (477) P-days have accumulated. A fungicide for early blight control is recommended. Commercial fungicide recommendations can be found in the 2013 Delaware Commercial Vegetable Recommendations Guide at http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Potato Disease Advisory #8 – June 21, 2013

Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County
Greenrow: May 5

Date

DSV

Total DSV

Accumulated

P-Days

Spray Interval Recommendation

5/15 – 5/20

11

32

5-days

5/20 – 5/23

2

34

5-days

5/23 – 5/27

5

39

5-days

5/27 – 5/30

0

39

10-days

5/30 – 6/6

2

41

251

10-days

6/6 – 6/7

10

51

261

5-days

6/7 – 6/9

10

61

280

5-days

6/9 – 6-13

4

65

314

7-days

6/16 – 6/20

13

78

377

7-days

 

Late Blight
The threshold of 18 DSVs has been exceeded. Seventy-eight (78) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. Favorable conditions have maintained the spray interval recommendation at seven (7) days. Late blight was confirmed on tomato in Montgomery County, Maryland and the eastern shore of Virginia. The website USABlight tracks tomato and potato late blight across the nation and can be found here: http://usablight.org/ Continue to scout your fields regularly for symptoms, especially since late blight has been found in neighboring states. Any suspicious samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local Extension office. See the 2013 Commercial Vegetable Production Recommendations-Delaware: http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Early Blight
We are using the predictive model WISDOM to determine the first fungicide application for prevention of early blight. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. We have now exceeded 300 P-days as of Thursday, June 13. Airborne Early blight inoculum should rise 5-10 days after accumulating 300 P-days. A fungicide for early blight control is recommended. Commercial fungicide recommendations can be found in the 2013 Delaware Commercial Vegetable Recommendations Guide at http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

 

Tomato Early Blight

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Early blight is one of the most common tomato diseases in the U.S. It occurs yearly in our region, but is most severe in periods of moderate temperatures and high leaf wetness. Early blight lesions may form on leaves, stems or fruit, and the lower (older) leaves are affected first. The lesions on leaves are dark with distinct concentric rings. They may be small, but can range up to ½ inch or more in diameter. Infected leaves may turn chlorotic. Early blight has become problematic this year because of our cool weather and high humidity. Many fungicides are available to manage early blight. Alternate a broad spectrum fungicide such as chlorothalonil, mancozeb, or Gavel with a more targeted material. Targeted fungicides include Cabrio, Endura, Flint, Fontelis, Priaxor, Quadris, Quadris Top, Revus Top, and Tanos. Remember to always alternate materials in different FRAC codes. Organic growers may find some benefit from use of OMRI approved copper products, or Sonata. All growers should maintain optimum, but not excessive nutrient levels to help the plants tolerate disease.

tomatoearlyblight

Early Blight on tomato foliage.

Potato Disease Advisory #7 – June 14, 2013

Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County
Greenrow: May 5

Date

DSV

Total DSV

Accumulated

P-Days

Spray Interval Recommendation

5/15 – 5/20

11

32

5-days

5/20 – 5/23

2

34

5-days

5/23 – 5/27

5

39

5-days

5/27 – 5/30

0

39

10-days

5/30 – 6/6

2

41

251

10-days

6/6 – 6/7

10

51

261

5-days

6/7 – 6/9

10

61

280

5-days

6/9 – 6-13

4

65

314

7-days

 

Late Blight
The threshold of 18 DSVs has been exceeded. Sixty-five (65) DSV’s have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. Favorable conditions have lowered the spray interval recommendation to seven (7) days. Late blight was reported in greenhouse tomatoes in Morgan County, WV over 7 days ago. The website USABlight tracks tomato and potato late blight across the nation and can be found here: http://usablight.org/ Continue to scout your fields regularly for symptoms. Any suspicious samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local Extension office. See the 2013 Commercial Vegetable Production Recommendations-Delaware: http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Early Blight
We are using the predictive model WISDOM to determine the first fungicide application for prevention of early blight. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. We have now exceeded 300 P-days as of Thursday, June 13. Airborne Early blight inoculum should rise 5-10 days after accumulating 300 P-days. A fungicide for early blight control is recommended. Commercial fungicide recommendations can be found in the 2013 Delaware Commercial Vegetable Recommendations Guide at http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Potato Disease Advisory #6 – June 7, 2013

Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County
Greenrow: May 5

Date

DSV

Total DSV

Accumulated

P-Days

Spray Interval Recommendation

5/5 – 5/8

18

18

7-days

5/8 – 5/12

3

21

7-days

5/12 – 5/15

0

21

10-days

5/15 – 5/20

11

32

5-days

5/20 – 5/23

2

34

5-days

5/23 – 5/27

5

39

5-days

5/27 – 5/30

0

39

10-days

5/30 – 6/6

2

41

251

10-days

 

Late Blight
The threshold of 18 DSVs has been exceeded. Forty-one (41) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. An additional five (2) DSVs have accumulated since the last report. The spray interval recommendation remains unchanged at 10 days for now. This could change by next week with today’s rainfall and the forecast predicting possible thunderstorms early next week. Scout your fields regularly for symptoms. Any suspicious samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local Extension office. See the 2013 Commercial Vegetable Production Recommendations-Delaware: http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Early Blight
We are using the predictive model WISDOM to determine the first fungicide application for prevention of early blight. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. A total of 251 P-days have accumulated at this site as of Thursday, June 6. Airborne Early Blight inoculum should rise 5-10 days after accumulating 300 P-days. The 300-P day threshold may be exceeded in the next week. A protectant fungicide application should be made once we exceed that threshold. Commercial fungicide recommendations can be found in the 2013 Delaware Commercial Vegetable Recommendations Guide at http://extension.udel.edu/ag/files/2012/03/Potatoes.pdf

Potato Disease Advisory #10 – June 23, 2011

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Little Creek, Kent County.
Greenrow: May 3

Date Late Blight Early Blight Spray Interval Recommendation
DSV Total DSV Accumulated P-days
6/6 1 58 251 10-days
6/6-6/8 0 58 263 10-days
6/8-6/9 0 58 267 10-days
6/10 2 60 274 10-days
6/11 4 64 282 5-days
6/12 2 66 291 5-days
6/13 0 66 301 7-days
6/13-6/15 0 66 318 7-days
6/16 1 67 328 7-days
6/17 0 67 336 7-days
6/18-6/19 0 67 352 10-days
6/20-6/22 0 67 377 10-days

 

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. We have surpassed the 300 P-day threshold for initiating early blight sprays.

Early Blight and Black Dot
Many fields have flowered and this is a good time to consider switching to an application or two of Gem, Headline, Quadris, or Evito (no black dot label) for early blight susceptible varieties. This can also be helpful for late season varieties including russets if stress makes plants susceptible to black dot later. Make one or two applications at the end of flowering and repeat 14 days later. Apply mancozeb or chlorothalonil 7-days later between the two applications. Another product that is labeled for early blight is Revus Top from Syngenta. Revus Top is a combination product of Revus (mandipropamid, Group 40) plus difenoconazole which is triazole fungicide (Group 3). Difenconazole has been used in Europe very successfully for early blight control. Since it is a different mode of action than the strobilurin fungicides (Group 11) it would be a good alternative if resistance is an issue if Gem, Quadris, or Headline are not controlling early blight.

For specific fungicide recommendations, see the 2011 Delaware Commercial Vegetable Production Recommendations Book.

 

Early Blight on Potato and Tomato

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

On both potato and tomato early blight produces large brown areas on the leaf, usually with a concentric ring pattern. On potato early blight usually begins after flowering on susceptible varieties, especially once potatoes or tomatoes begin to senesce. The disease is favored by high humidity and periods of leaf wetness. Optimal temperatures for infection range from 75-80°F.

Control of early blight begins with crop rotation then protectant fungicides, such as chlorothalonil or mancozeb, should be applied every 7 to 10 days, depending on the weather. Once flowering occurs on potato a systemic fungicide is recommended for several sprays, especially if a susceptible variety is grown or early blight is found in the field. Systemic fungicides recommended for early blight control on potato include: Endura, Gem, Headline, Quadris, Reason, Revus Top, and Tanos. As always, follow pesticide labels for rates and usage. Revus Top and Tanos will also offer suppression of late blight. See the Potato Disease Advisory for P-day accumulations to predict early blight appearance. The same fungicide list applies for tomato, just substitute Cabrio for Headline. Alternate the protectant fungicide with the systemic fungicide combined with a protectant as per label instructions.

Early blight on potato

Early blight on tomato