Asparagus plagued by rust


A few years back, you mentioned asparagus as one of five crops which would grow here nematode-free. I put in a bed about 30 feet long — an enormous amount of work. At first, things were fine, but now I have rust. The websites I have consulted list no cure and advise selecting rust-resistant varieties. Too late for that. I tried to find something on the CTAHR (University of Hawaii at Hilo College of Tropical Agriculture and Human Resources) site but found it impenetrable.

Do you know of anything I can do other than keep the bed free of dead and dying canes?

I also have a severe thrips problem. Spring onions are a failure, and now they’re in my leeks. I planted a new bed under Agribond but the wind tore holes in it.

I have tried putting up sticky traps; they appear to have had no effect. What can I do?

Thank you so much, and if you can tell me how to find answers on the College of Tropical Agriculture site, I will stop bothering you. Gratefully, A.P.

It is no bother to help in efforts for a productive garden! Now let me start by discussing the asparagus problem.

According to the CTAHR publication on asparagus, “There are no serious problems with insects or diseases of asparagus in Hawaii. The foliage, however, may become infected with a rust fungus during wet periods.” To have some rust infection is tolerable so my advice is not to pull the plants yet; the disease should not kill the asparagus plants.

Pruning heavily infested ferns and disposing of them is the first step. By disposing, I mean, do not leave them on the ground or place in the compost pile. If the rust is infesting many or all of the ferns, cut out as many as possible.

Since the harvest process calls for cutting the ferns back about every 5-6 months, this would be a good time to remove and dispose of infected ferns. Asparagus ferns can also be sprayed with sulfur; it has been reported effective against rust, unless the infestation is severe.

As for the second problem, onion thrips is a major insect pest not only of onions and leeks but also attacks broccoli, cabbage, carrots, cucumbers, garlic, melons, papaya, pineapple, squash and tomato. (Note: Thrips refers to one or many.)

The damage from the feeding results in whitish or silvery streaking on the leaves.

Black droppings from the insect may also be seen. Thrips populations are often greater in the warmer months of the year.

There are predators and parasites that attack the thrips but often are not effective for proper control. Sometimes washing with a stream of water will help. Plants, of course, will tolerate a certain level of infestation causing only cosmetic damage. If injury threatens crops loss, then treatment is called for.

Synthectic pyrethroid insecticides such as Warrior (lambdacyhalothrin) and Ammo (cypermethrin) are effective in controlling onion thrips.

“Bulb Onion Production in Hawaii” by R. Hamasaki and H. Valenzuela is a publication available on the CTAHR website.

Lastly, for those not familiar with the CTAHR website, go to http:// www.ctahr.hawaii.edu/Site/Info.aspx and on this page enter a gardening topic in the box or browse publications. On the same page, click on “Knowledge Master” or “Farmers Bookshelf,” these pages give ample information on various crops and pests. Under “Knowledge Master,” go to “Information on Agricultural Pests” to find out about insects and diseases of various crops. An alternative address for CTAHR is http://www.ctahr.hawaii.edu/site/.

Did you know?

A corm is thickened underground storage tissue formed usually by the enlargement of the base of the main plant stem. A common example is taro, along with gladiolus and crocus.

A tuber is an enlarged fleshy underground stem and in most cases acts as a storage organ. The most common example is the potato.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net.

 

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