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Fruit and Vegetables |
Anthracnose symptoms are prevalent in many fields, especially those with no history of fungicides. We also have been monitoring populations on leaf tissues and in plants and find that the pathogen can be widely distributed in plantings and commonly found on green leaf tissue that shows no symptoms.
Many flowers have anthracnose blight or berries have blackened tips as previously shown. The anthracnose pathogen has colonized the flower or fruit and has grown into the berry stem. Figure 1 shows the flower after it has been incubated for a couple of days. The pathogen has produced many spores that can spread through the planting with wind driven rains.
Figure 2 shows plants with no anthracnose. Figure 3 represents plants inoculated with Colletotrichum acutatum in our Castle Hayne research trials. The anthracnose has caused plant stunting and a lot of variability in plant growth. We inoculated plug plants with anthracnose about 10 days before field setting and then applied fungicide drenches and sprays.
The newest leaf may emerge but turn brown due to anthracnose infection (Figure 4). Also note the blighted fruit. Figure 5 shows typical lesions of the leaf petioles due to the anthracnose pathogen.
In the last few days I also have received many plants with marginal browning of leaves. This resembles drought injury or fertilizer burn but may be due to anthracnose. This has not been confirmed but such plants have a slight discoloration in the crowns similar to problems we saw in 1999. The browning off the eaves may occur in one or more crowns or affect the entire plant. Typically, the problem shows up scattered in a field. (Figure 6; Figure 7)
We also have been seeing some Botrytis crown rot due to all the wet and cloudy weather. This appears to be scattered and at low levels, especially in fields where fungicides have been applied. However, it is a reminder that the recent weather patterns have been very favorable for gray mold.
We have received many inquiries regarding fungicide programs. The sense is that if the planting is at risk for anthracnose, maintain an aggressive program that includes Captan and Quadris or Cabrio. If wet conditions prevail, it is advisable to include a good Botryticide such as Elevate or Switch as previously discussed (Schedule 3). If the field is not at risk for anthracnose, focus on Botrytis management (according to Schedule 1).
Regretfully, many plantings that have anthracnose also have the angular leaf spot. We often do not see a decrease in yield due to this disease but many times the pathogen will grow on the green calyx of the fruit and turn it black, making it unsightly. There is very little good data concerning management of this problem. It may be wise to incorporate copper in a spray program during wet weather and as the fruit is sizing in an attempt to limit damage to the calyx. Currently we suggest no more than 3 to 4 copper sprays in a season to avoid phytotoxicity problems. Warm dry weather is the best control for this disease and hopefully the weather will turn around.
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Last modified on April 21, 2003 by Stephen J. Toth, Jr.
