This edition of the OSU Extension Fruit & Vegetable Report was written using field observations and expertise from the following OSU Extension staff: Frank Becker, Thomas Becker, Chris Galbraith, Gary Gao, Melanie Ivey, Carri Jagger, Dan Lima, Diane Miller, Francesca Rotondo, Ryan Slaughter
Vegetables
Tobacco hornworm. Photo by Ryan Slaughter, OSU Extension.
Hot, humid conditions have brought upon bacterial diseases in fruiting vegetables. Management of bacterial diseases can be challenging and frustrating. Foliar bacterial diseases are best managed with an integrated approach of sanitation, selection for disease resistance, and application of effective bactericides. There are 2 main groups of bacteria that cause diseases in plants, and they are Pseudomonas and Xanthomonas. Pseudomonas has a favorable temperature range of 60-75 degrees fahrenheit. Xanthomonas has a favorable temperature range of 77-86 degrees fahrenheit. Once present on the plant, the bacterial infection may appear to be inactive during periods of unfavorable conditions, however, the infections become active again when conducive environmental conditions return.
Symptoms of bacterial disease present on leaves and fruit of tomato. Photos by Frank Becker, OSU Extension.
Bacteria can be easily spread via splashing rain, plant to plant contact, human activity, insect activity and on equipment. It is critically important to properly diagnose foliar lesions observed in your crops to allow you to take proper care and precaution, especially if the disease is found to be bacterial. Aside from using clean seed and following proper sanitation practices and other cultural crop management recommendations, utilizing chemical control products such as copper, mancozeb, certain botanical oils and Bacillus species can help to combat bacterial infections. Always read the label to ensure that the product that you are considering using has activity against bacterial pathogens.
Pith necrosis, also a bacterial disease, has been observed in tomatoes. The only strategy for managing pith necrosis is prevention by avoiding favorable conditions, in particular excessive nitrogen. Copper fungicides are not able to provide control because this soil-borne bacterial pathogen is inside the plant.
Fungal diseases are also being reported, including Septoria leaf spot in tomatoes and Alternaria in melons. Downy mildew (clade 2 that affects cucumber and cantaloupe) has been found in at least five Ohio counties to date. Samples with yellow vine decline and bacterial wilt have been coming into the diagnostic lab. A reminder that when sending samples into the lab, make sure to include the full plant with roots if possible.
The 2nd generation of flea beetles continues to cause trouble in young cole crops. Spider mites are also seeing an uptick with the recent scorching weather. Corn leaf aphids are being observed around the Great Lakes region, affecting mostly sweet corn.
Corn leaf aphids on sweet corn tassel. Photo by Chris Galbraith, OSU Extension.
It’s getting to be that time of the year where we might have some of our early crops reaching the end of their productivity. Whether it’s cucurbits or cole crops or anything that we got planted early, we are now left with trying to figure out what to do with this now unproductive space in our field or garden. You have a couple of options:
Succession Planting: You may decide that you really don’t want to be done with growing something just yet. You could consider succession planting. Succession planting is a way for you to grow a crop throughout more of the growing season, instead of, for example, just growing a cool-season crop in the spring and being done for the rest of the season or waiting until you can plant warm-season crops and only having the one crop for the season. In the right circumstances, you could have an early cool-season crop, followed by a warm-season crop, followed by another cool-season crop depending on the amount of time it takes each crop to reach maturity. For example, you might plant something like lettuce or radishes early in the spring, then after you have harvested that crop, you might come in and plant something like beans, tomatoes, peppers, etc.
Done for the season: Maybe you are done planting new crops for the season, and that’s just fine! There are some best management practices though we can implement to make sure we are keeping our other crops protected and healthy. If you have a crop that is done producing, and perhaps starting to senesce, it is best to remove that plant material from the garden or field. Even though you might be done with the plants, pests and diseases certainly are not. If left in the garden or the field, this plant material can serve as a harborage for pests and diseases that could still impact our crops that are still growing. Removing this plant material gets rid of a favorable environment for things that would otherwise pose a threat to the rest of our garden or field. You can either physically remove the plant material and burn it or compost it, or you could work it into the garden or field to bury the plant material.
So, whether you are done with an area in your garden or field or if you plan to keep planting, don’t just leave all that plant material behind. End of season best management practices can set us up for success for the rest of this season and for the next growing season!
Fruit
Hot and dry weather has continued to promote population development of European red mites and two-spotted spider mites. This problem can be made worse with applications of certain insecticides that wipe out beneficial insects and natural enemies that would otherwise be keeping the mite population in check. Codling moth and oriental fruit moth seem to be slowing down in eastern Ohio.
Strange spots were observed on apple across the Great Lakes region. Some cases from other states have been confirmed as blister spot (Pseudomonas). Blister spot tends to occur more frequently in cool, wet weather which has not been characteristic of the season in much of Ohio. The apple variety Mutsu is particularly susceptible to blister spot. Ohio cases were not found to be bacterial in nature – final diagnosis concluded the symptoms were likely due to spray injury that occurred during recent high temperatures.
Blister spot in apple. Photo source: John Hartman, University of Kentucky, Bugwood.org.
Some apple trees this year were observed to have “mummy” fruit that didn’t size up and develop properly but still remained on the tree. MaxCel, a plant growth regulator used for thinning, seems to cause this issue in some years with different varieties. Going back through to hand-thin is too labor intensive and so growers often resort to having workers just harvest around the undeveloped fruit.
The hot weather has also resulted in sunscald concerns in small fruit and orchards. Once sunscald occurs, the fruit can become susceptible to other pathogens and secondary pests.
Strawberry foliar and crown rot diseases seem to be widespread this year. Much of the management for this is preventative, such as practicing sanitary propagation methods. Blueberry season is wrapping up in many areas. High tunnel blackberries are being harvested and field blackberries are close to ripening in northern Ohio. Blackberry yields have been high in central and southern Ohio. Newer blackberry varieties such as Ponca that been planted more and more in recent years have lower acidity and are sweeter, improving sales and customer satisfaction.