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Showing posts from August, 2016

Bacterial diseases of vegetables

M. Grabowski, UMN Extension Educator
The high heat and humidity this summer, combined with multiple heavy rain events have created ideal conditions for many bacterial plant pathogens to multiply and spread. This is especially evident in the vegetable garden, where black rot can be easily found on cabbage, kale, and broccoli, beans bear spots and browning from bacterial leaf blights, and tomato and peppers are spotted by bacterial spot.
Bacterial plant pathogens have several unique features that make them good plant pathogens. Many are able to infect seed and can be introduced into the garden unseen on infected seed or transplants.

Bacteria are covered in a sticky coating and are easily spread through the garden on hands, tools, and insects. Many bacterial plant pathogens are also easily spread by splashing rain or sprinkler irrigation. Bacteria infect the plant through natural openings or wounds. They multiply within infected plant tissue and can survive from one growing season to t…

Springtails in homes

Jeffrey Hahn, Extension Entomologist

A consequence of the abundant rainfall that most of Minnesota has received has been an increase of springtails found in homes and other buildings. Springtails are small insects that are associated with moisture. They range in size from 1/16 - 1/8 inch in length. Most are slender, although some are round and stout. They are typically dark colored, gray, black or brown, but some are white and some even iridescent and brightly colored. Springtails lack wings but do have the ability to jump.

Springtails as a group are very numerous, living in a variety of moist habitats including in soil, leaf litter, mulch, decaying wood, and around bark where they feed on fungi, pollen, algae, and decaying plant matter. They can live inside buildings when high moisture exits, e.g. around plumbing leaks. They can also seek shelter indoors when areas around the outside of the home become excessively wet. Fortunately, regardless of the number that are seen, t…

A bad year for bur oak blight

M. Grabowski, UMN Extension Educator
This summer many bur oak trees are suffering significant leaf browning and death due to bur oak blight. Frequent rain events at the time new leaves were reaching their mature size created highly favorable conditions for infection by the fungus that causes bur oak blight. For property owners with affected bur oak trees, now is the time to submit a sample for diagnosis. If disease is severe, contact an arborist now to schedule treatment for bur oak blight in spring of 2017.
Bur oak blight, often referred to as BOB, is a plant disease caused by the fungus Tubakia iowensis. The BOB fungus survives the winter on infected leaves that remain attached within the tree canopy.  In wet spring weather, the fungus releases spores that start infections on new leaves. Although the infections occur in spring, the most obvious symptoms do not appear until the end of July or early August. Initially, dark discolored lines can be seen forming along major leaf veins. As…

Useful Tools to Determine Soil Moisture Status II: Gypsum blocks and others

Karl Foord, Extension Educator - Horticulture

Another tool for measuring soil moisture are gypsum blocks. Gypsum is a porous material that equilibrates with soil water similar to the ceramic tips of the tensiometers. In this case two electrodes are embedding in the gypsum block in a cylindrical or parallel mode (Figure 1). The commercial product often has a perforated metal covering to protect the gypsum (Figure 2).
This system functions by connecting to a meter that measures the resistance between the two electrodes embedded in the gypsum. Water is a good conductor of electricity. As soil water decreases due to plant draw down resistance increases and visa versa when soil water increases resistance decreases. The electrodes can be permanently connected to a box (Figure 3) or temporarily connected to a portable meter (Figure 4).

Placement of gypsum blocks follows the same strategy that is used with tensiometers. One block is placed in the middle of the fibrous root zone and another b…

Useful Tools to Determine Soil Moisture I: Tensiometers

Karl Foord, Extension Educator - Horticulture

Generally the most limiting element in maintaining uniform plant growth and high quality produce is water. A plant can be experiencing water deficit prior to our observation of wilting. Such deficits can lead to slower growth rates, pollen mortality and loss of flowers, lighter fruit weight, and blossom end rot, among others. It is best to avoid having the plant experience any water deficit.

However, how can you know that the plant is in water deficit? The truth is that you can only know this indirectly. One can estimate soil water content by taking a soil surface sample and feeling the water content with your hand; this will of course vary with soil type and again extrapolates the soil water content within the root zone. This method will require consistent attention to growing conditions including temperature humidity and rainfall.

What  other options might allow a more direct sampling of soil water content within the rooting zone of the …

Bugs on milkweed

Jeffrey Hahn, Extension Entomologist

Home gardeners have been finding orange and black insects on their milkweed and related plants. Although some people think they are boxelder bugs, they are actually insects called large milkweed bugs, Oncopeltus fasciatus.

Adults grow as large as ¾ inch long. They are mostly orange and black including a black horizontal band across the center of the body and black on the end of the wings (the membranous section). A portion of the head is reddish orange. The immature nymphs are mostly orange with black wing pads and smaller than the adults.

Large milkweed bugs prefer to feed on common milkweed but will also feed on other related species. They often feed in large groups making them conspicuous on the plants. Despite their appearance, they do not harm milkweed nor any insects, like monarchs, they may also be on the plants. No action is necessary if large milkweed bugs are found in your garden.

Sap beetles in gardens

Jeffrey Hahn, Extension Entomologist

Some home gardeners have been finding sap beetles in some of their fruits and vegetables. These beetles are generally small, between 1/8 – ¼ inch long, oval, and dark colored. Some sap beetles have orange spots on their wing covers.
Sap beetles are attracted to fermenting smells and will attack fruits and vegetables, such as tomatoes, sweet corn, raspberries, strawberries, and muskmelons, that are damaged, overripe, or rotting. They often are just a nuisance, although it is possible for them to move to and damage ripening fruit.

The best management for sap beetles is to pick fruits and vegetables regularly as they ripen and remove any damaged or overripe produce in your garden and dispose of by burying or bagging them. This helps eliminate smells that could attract them to your garden. However, once sap beetle find your garden, they can be challenging to eliminate.

Insecticides, such as carbaryl or permethrin, can kill sap
beetles and …

Extension publications: New & Revised in 2016

Lawn Irrigation Survey and Water Saving Strategies

The Metropolitan Council and University of Minnesota Extension are conducting a survey to assess irrigation practices throughout the 7-county Twin Cities Metropolitan Area.  This survey is part of a larger project with the ultimate goal of reducing water use in the home landscape.  You can help us by taking 10-15 minutes to answer a 30 question survey regarding your irrigation practices.  All survey participants will be entered into a drawing for 1 of 10 Visa Gift Cards ($50 value).  Additionally, we are conducting irrigation audits for many properties throughout the Twin Cities.  To have your home irrigation system audited, please complete the survey and indicate that you would like to receive a free audit.  To access the survey, please follow click the hyperlink below: 


Basic water saving strategies for home lawns Pay attention to the weather During a Minnesota summer we may see heavy periods of rainfall followed by extended periods of drought. Homeowners …