Friday, October 30, 2009

Hop Pest Problems

I have just got back my latest report card from the Plant Pathology Lab in Raleigh. They are a little slow getting things done down there so by the time I got back my report, the bugs had already destroyed my entire crop! Whoa there, just kidding, but they are slow. I would assume that they have a large volume they are dealing with?

What I have found from this report and one submitted previously about two months ago is that I have no plant disease problems. This was good news of course on that front, but I did find some bad news as well. Seems that I have spider mites and leaf hopper infestations.

To keep myself informed on the disease and pest problems that can affect hops, I bought the "Compendium of Hop Diseases and Pests". The book is expensive, but worth it if you are going to be involved with this crop. I was able to get it on Amazon for $65. Compendiums are available for many different crops as well, full of slick pictures and info.

The Hops Compendium

So, back to the problem at hand. I have decided to look at biological control methods, keeping my production organic so far. After doing research on the two-spotted spider mite, I was able to find some beneficial mite predators listed. After a quick trip to the hop yard, I brought back a couple of samples of leaves for inspection.

To my surprise, I don't think I found any spider mites. Instead, I found what I think is one of the beneficial predators called a Phytoseiulus Persimilis. This guy feeds on all stages of the spider mite and consumes 2-3 adults or several dozen eggs a day. It is also suited to the cooler and wetter climates that we have here.

The "Mighty Mite" Phytoseiulus Persimilis

So, get out your hand lenses and start looking. This photo was taken with a hand lens. P.Persimilis is about the size of the tip of a very sharp pen. Remember, be careful if you are going to spray for spider mites. That spray may also be killing the "good guys" as well.

1 comment:

  1. Van:
    I am the specialty crop entomologist who looked at your clinic sample this fall. I came across your blog and wanted to encourage you to drop me a line about your hop pest issues. The clinic is a good resource for out of the ordinary problems, but I have a much shorter response time directly. The mite pictured about is probably not P. persimilis (it's a little too red) and maybe either a European red mite or carmine spider mite. Both of these are potential pests.

    You can reach me at or via my blog:

    I look forward to hearing from you and wish you a good upcoming field season.

    Hannah Burrack
    Assistant Professor & Extension Specialist, NCSU