Posts Tagged ‘strawberry diseases’

Strawberry Angular Leafspot

Thursday, March 29th, 2012

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

There have been several samples from DE and MD with angular leafspot that have been diagnosed this spring. As you can see from the picture this bacterial leafspot produces angular watersoaked spots initially (Figure 1) that turn dark and eventually brown with time (Figure 2). The bacteria are limited by the vein pattern in the leaf which gives it the diagnostic angular pattern. This disease can cause leaf loss, and when conditions are very favorable during fruit set, the calyx can become infected and that can reduce the marketability of the fruit. Wet conditions favor the disease, especially if irrigation is needed for frost protection. The bacteria that cause the spring symptoms come from systemically infected overwintered plants and dead leaves, and from infected transplants. Copper sprays can be effective in limiting spread once it is identified but over-application can be phytotoxic, so be careful. Prevention of angular leafspot in the plant nursery and its dissemination in transplants is crucial to controlling this disease.

Figure 1. Watersoaking symptoms

Figure 2. Angular leafspot symptoms

Mustard Seed Meal as a Chemical Fumigation Alternative

Thursday, August 4th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

With September strawberry planting season approaching for the annual plasticulture system, growers will be preparing beds and fumigating in the next 2 weeks. While several chemical fumigants are registered for strawberries, new fumigant use restrictions will make their use more of a challenge. In addition, strawberry growers that are organic or are using high tunnels with limited rotation are looking for effective fumigation alternatives.

One natural fumigant alternative that has shown great promise is mustard seed meal. According to researchers Dean Kopsell and Carl E. Sams, “studies conducted at The University of Tennessee showed that mustard seed meal has extremely high concentrations of isothiocyanates (ITCs). The seed meal is also a fertilizer source of nitrogen and other nutrients. When incorporated into the soil, ITCs act as effective biofumigants, reducing populations of pathogenic fungal species (Sclerotium, Rhizoctonia, Phytophthora, and Pythium), nematodes, weeds, and certain insect species.” ITCs are the same compounds found in some commercial chemical fumigants.

Specific studies with strawberries showed yield increases of as much as 50% compared to untreated controls using mustard seed meal. Additional research is going on in the region (Virginia, Maryland, Delaware, and Pennsylvania) with this material.

For mustard seed meal to be effective as a fumigant it has to be thoroughly worked into the bed area and plastic layed immediately after incorporation. The bed must remain evenly moist so the meal can break down (dry pockets will have delayed break down and can cause problems later) so a moist soil is important. A waiting period of 20 days is advised similar to a commercial fumigant before planting.

Current supplies of mustard seed meal come from Tennessee and costs $1.00-1.20 per pound. Recommended rate is 1000 lbs per mulched acre.

Because mustard seed meal is a natural compound, fumigant restrictions do not apply. It is also OMRI certified for organic production.

Fungicide Recommendations for Strawberry Disease Control

Friday, May 6th, 2011

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

Anthracnose Fruit Rot
Strawberry anthracnose can be extremely destructive during warm, wet weather causing significant fruit rot. Symptoms of anthracnose include blackish-brown circular spots on maturing green fruit and soft, sunken (flat) circular lesions on ripe fruit. On ripe fruit, lesions can expand rapidly and are often covered with a pinkish-orange spore mass. Spores are spread from infected to healthy fruit with splashing water. Control of anthracnose always begins with a 7 to 10-day preventative spray program no later than 10% bloom and/or prior to disease development. For control apply the following combinations:

Application #1:
captan (M3) at 4.0 lb 50WP/A plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A

Application #2:
captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl. oz 2.08SC/A
or
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A

Application#3:
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

For subsequent applications, alternate:
captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A
or
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A plus captan (M3) at 4.0 lb 50WP/A
or
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

To help manage fungicide resistance development, do not make more than 2 consecutive applications of either:

Pristine (pyraclostrobin + boscalid, 11 + 7), Cabrio (pyraclostrobin, 11) or Abound (azoxystrobin, 11) before switching to another fungicide chemistry.

Botrytis
Botrytis (gray mold) and blossom blight can cause serious losses in strawberry plantings in high tunnels and the field if not controlled properly. Development is favored by moderate temperatures (59 to 77°F) with prolonged periods of high relative humidity and surface wetness. Control of gray mold begins with preventative fungicide applications. Apply at 5 to 10% bloom and every 10 days until harvest. During periods of excessive moisture, spray intervals of 5 to 7 days may be necessary. Rotate fungicide chemistries to aid fungicide resistance management.

Application #1:
captan (M3) at 4.0 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP/A
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A

Application #2:
Elevate (fenhexamid, 17 – See restrictions) at 1.1 to 1.5 lb 50WDG/A
or
Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz. 38WG/A

Application #3:
captan (M3) at 4.0 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A

For subsequent applications, alternate:
captan (M3) at 4.0 lb 50WP/A
or
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A.

From Rutgers Plant and Pest Advisory, Veg Crops Edition, by Andy Wyenandt, Ph.D., Specialist in Vegetable Pathology and Wesley Kline, Ph.D., Cumberland County Agricultural Agent

 

Strawberry Angular Leafspot

Friday, April 8th, 2011

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

There have been two samples of angular leafspot that have been diagnosed this spring. One sample was from high tunnel production, the other annual strawberry under row covers. As you can see from the picture this bacterial leafspot produces angular watersoaked spots initially (Photo 1) that turn dark and eventually brown with time (Photo 2). The bacteria are limited by the vein pattern in the leaf which gives it the diagnostic angular pattern. This disease can cause leaf loss, and, when conditions are very favorable during fruit set, the calyx can become infected and that can reduce the marketability of the fruit. Wet conditions favor the disease, especially if irrigation is needed for frost protection. The bacteria that cause the spring symptoms come from systemically infected overwintered plants and dead leaves, and from infected transplants. Copper sprays can be effective in limiting spread once it is identified but over-application can be phytotoxic, so be careful. Prevention of angular leafspot in the plant nursery and its dissemination in transplants is crucial to controlling this disease.

Photo 1. Watersoaking symptoms

Photo 2. Angular leafspot symptoms.