Monday, June 12, 2017

Magnesium deficiency symptoms

Dr. Ajay Nair and Kristine Neu
Department of Horticulture
Iowa State University

Iowa is finally getting some nice warm, in some cases hot, sunny days. This reigns in the importance of irrigation and supply of nutrients to plants for rapid growth and development. Nutrient deficiencies often show up with rapid plant growth. One we are observing now is magnesium deficiency.


A typical indicator of magnesium deficiency in vegetables is interveinal chlorosis which develops between the leaf veins (first image). Due to magnesium’s mobility in plants, symptoms will typically affect older leaves first. Prolonged deficiency will eventually lead to death of the tissue (second image). Magnesium deficiency is widely observed in vegetable crops, particularly pepper and tomatoes due to their nutrient high requirements. To address deficiency soluble magnesium sources, for example Epsom salt, could be used both foliarly or through the drip. Foliar applications are effective but must be applied in low concentrations to avoid phytotoxicity. For smaller areas and backpack type operation, mix 1 lb of Epsom salt in 5 gallons of water and spray uniformly. For fertigation apply 15-25 lbs of actual magnesium per acre.

Friday, April 28, 2017

Iowa Cover Crop Survey

Ajay Nair
Department of Horticulture
Iowa State University

Cover crops can improve soil health, conserve resources and improve farm profitability. Now, your experience with what works and doesn't work can help shape the future of cover crop initiatives nationwide. Farmers who plant cover crops, used to plant cover crops, or have never tried cover crops are all encouraged to take this short survey, now in its fifth year.

Please take the survey at

Wednesday, April 12, 2017

Colorado potato beetle management

Dr. Ajay Nair
Department of Horticulture
Iowa State University

Ames, IA. Recently I was contacted by a fellow grower and good friend Ms. Laura Krouse from Abbe Hills Farm, Mt. Vernon, IA with a question regarding common enemy of ours: Colorado potato beetle (CPB). Given the mild winter we have had, CPB could pose a formidable challenge this year. If you follow strict crop rotation plans and have moved your potato plots around, hopefully 650 ft, you should be ok but it is always good to be prepared. Why is 650 ft? That is because research shows that CPB in their early development stages emerge from the soil and walk to find potato plantings and 650 ft is to much of a hike for them !

Anyways, let us briefly discuss few management aspects especially insecticides, both organic and conventional. Growers who use conventional insecticides are number of options, some commonly used insecticide classes include pyrethroids (Warrior, Mustang, Asana, Baythroid), carbamates (Sevin), and chloronicotinyl (Actara, Admire, Assail, Platinum), to name few. It is also important to rotate insecticides between different chemical classes. Repeated use of same insecticide can lead to resistance issues in CPB. 

Now, what about organic management. Bacillus thuringiensis products are effective but not all strains. Bacillus thringiensis var tenebrionis provides effective CPM control, however, it is only effective against small larvae (less than 1/4 inch) and should be applied at egg hatch or when larvae are first seen. When the larvae get larger than that, it is more difficult to control with Bt. A commercial OMRI approved product containing Bt tenebrionis is Trident® (Certis USA Inc.). One can also use neem-based products such as Azatin-O, which is OMRI approved. Botanical insecticides, such as neem, have limited persistence in the environment as the temperature, ultraviolet light, rainfall and other environmental factors can degrade neem. Repeated applications may be needed but apply based on label instructions to avoid any kind of phytotoxicity.

Sunday, January 29, 2017

Tomato grafting

Ajay Nair and Kristine Neu
Department of Horticulture
Iowa State University

High tunnels have emerged as a tool for Iowa vegetable growers to extend the growing season, increase crop production, and improve the quality of the produce, but production in this system does not come without challenges. Continuous cropping of tomatoes in the same high tunnel gives rise to recurring soilborne and foliar diseases, pest pressure, issues with soil fertility and salinity, and increased irrigation requirements. One tool to overcome these challenges may be the use of vegetable grafting. The process of grafting is accomplished by attaching the desired scion onto a rootstock that is typically bred for vigor and/or disease resistance.

Results from a two-year study of grafting a determinate (Mountain Fresh Plus) and an indeterminate (Cherokee Purple) tomato cultivar on RST-04-106T rootstock are available on sustainable vegetable production lab website. Click on the link below to download the report.

Wednesday, January 18, 2017

It is all about seeds !

Dr. Ajay Nair
Department of Horticulture
Iowa State University

This is the time everyone is busy planning for the upcoming season and for some time to order seeds. A successful cropping season rests largely on high-quality seeds. Seed quality is central when it comes to uniform germination, successful establishment, and high yields of vegetable crops. Key factors growers should be aware of:

1.       Seed storage: It is always good to buy new seeds every year but if you have leftover seeds from last year, you can still use them, provided they were stored properly (low moisture, cool, and dry storage conditions). It is better to avoid seeds that are more than 2 years old that were not properly stored.

2.       Cultivars: It is a good time to glean through university cultivar trial reports, extension publications, grower forums, and seed catalogs to identify the cultivar you want to grow. Use your own experience from previous growing seasons and customer feedback to make the right cultivar choice. Of course, there is nothing wrong in experimenting few new cultivars and vegetable types.

3.       Seed suppliers: Please make sure to order seeds from reputed and trusted vendors. Seeds should have high germination percentage, should be true to type, free of weeds and diseases. Sometimes it is better to call your area seed company representative. The Iowa Fruit and Vegetable Growers Association Conference (26-27 January 2017, Ankeny, IA) will host several seed companies that do business in Iowa. More information on

4.       Order the right amount: It is advisable to order a little more than what you need but it is not good to order large quantities of seeds that go unused.

To sum it all, seeds are the foundation of a successful production system. Seed quality plays an important role and its characteristics such as trueness to variety, germination percentage, purity, vigor, and appearance are important for optimum crop growth, performance, and yield. A good quality seed never costs, it pays!