Aster Yellows

As with most disease and pest problems, accurate diagnosis is the important part of controlling a problem and doing so responsibly.

In this case, the image shows aster yellows disease on a purple coneflower. Aster yellows is a disease that is spread through insects that suck on the sap of plants. In most cases, it’s the aster leafhopper that is the carrier of the pathogen.

Aster yellows creates distorted flowers with green tufts, chlorosis of the leaves, stunted growth, and green flower petals. Different species may exhibit slightly different symptoms.

It can spread among plants in the Aster family as well as hundreds of other plant species outside of the Asteraceae family. Including lettuce, garlic, carrot, tomato, chrysanthrmum, petunia, zinnia, coreopsis, and perennial weeds like dandelions.

Unfortunately, if you see signs of aster yellows the entire plant needs to be disposed of to avoid spreading the disease. There is no treatment since it becomes a systemic issue and travels down into the roots. Burn your plant or bury it in your compost so it’s completely covered. The disease will not survive once the plant is dead.

You can plant something else as a replacement as it will not transfer through the root system.

Dry and hot summers slow the spread of the aster yellows disease, while cool and moist summers may accelerate transmission.

*Note for MN residents. It is illegal to dispose of plant material in your trash bin. Especially noxious weeds. Letting them die on site is the best way to mitigate further spread. Choose an area, above ground to pile weeds and pull weeds that germinate.

Read more on extension.umn.edu/plant-diseases/aster-yellows

Blight Resistant Tomatoes and Prevention

All fresh tomatoes are great but those of you who are looking for tomatoes that are blight resistant, look no further!

Brief description of blight:

Blight causes sudden yellowing, wilting, spotting, or browning of new leaf growth, fruit, stems, or the whole plant, depending on the severity. It spreads by fungal spores that are carried by wind, water, tools, and insects from infected plants, and then deposited on the plant or dead plant matter on the soil. The disease requires moisture to progress, so when moisture or rain comes in contact with fungal spores, they reproduce. The spores thrive in humidity and the spores can then be transmitted through the wind easily.

Blight can infect many different plants, i.e.  apples, potatoes, and cucumbers, and can be caused by various fungal strains like Alternaria solani, a.k.a. Early Blight, or Phytophthora infestans, a.k.a. Late Blight.

Prevention is key, even for blight resistant tomatoes. Copper fungicide, or Fung-onil can help slow the growth once you see signs of blight or spray on the plant prior (about 2 weeks) before predicted hot and humid weather.

Example of early blight on a tomato leaf. Source: Univ. of MN Extension

Best practices to prevent blight:

• Healthy plants are less effected by blight. Provide proper water and nutrients. Tomatoes are heavy feeders. Tomato Tone or Plant Tone are good options when you are first planting your tomatoes. If you get a lot of foliage growth, fertilize with less nitrogen and more phosphorus, 5-10-5.
• Mulch around your plant to prevent soil from splashing up onto the foliage.
• Water your plant at the base and avoid the foliage. Morning is best so it can dry throughout the day.
• Provide proper spacing between plants and air flow but using cages.
• Sanitize all garden tools between plants
• Clean up any dead infected foliage around the plant and either burn or put into the trash. Do not compost!
• Prune the lower branches of tomatoes a foot above the ground to help reduce water splashing on the leaves.  Prune further if you see any disease spots on lower leaves.

Don’t let diseases deter you from certain plants since many plants can get blight without proper care, prevention, or crop rotation. If you have been effected by blight, we understand the frustration, so try one of these blight resistant varieties listed below. If we have especially hot and wet weather, we recommend having a fungicide on hand so if you start seeing blight, you can treat a.s.a.p.

BLIGHT RESISTANT TOMATOES

*All listed container plants will also do well in the ground. These tomato plants tend to have a more compact size.

Determinate = Plant grows to a certain size and stops, bearing most of it’s fruit within a one month period. Great for small spaces or containers. Some will grow tall and still need tomato cages.

Find pictures to help identify blight, from University of Minnesota Extension, as well as more management information.