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 MOFGA's 2011 Pest Reports - Compiled by Eric Sideman, PhD Minimize

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MOFGA's Pest Report - June 1, 2011
Compiled by Eric Sideman, PhD - MOFGA's Organic Crop Specialist


Clipped bud (above). Clipper early feeding damage (below). Photos by Eric Sideman.
Strawberry Clipper:
The damage has been done by now and there is nothing to do about it. But large scale growers should be out assessing the damage and making the decision if it is time to rotate.

As with many of the problems of strawberry production, crop rotation to a distant field is the only way to manage the clipper.

For homeowners who just have a small patch of strawberries, now is the time to get out with a container and collect all of the clipped buds and destroy them.

The strawberry clipper is a small, copper to black snout nosed beetle. In the spring they emerge from overwintering as adults and begin feeding on pollen by poking holes into the bud (you will see holes in the petals when the flowers open).

Later the females lay eggs in the buds and then crawl down and girdle the bud so it hangs by a thread and dies. Each dangling bud has an egg in it. Each female can lay up to 300 eggs. These buds fall to the ground and development of next year’s clippers begins. You can see how a population of clippers can build very quickly over a few years in a strawberry field. That is why it is time for gardeners to collect those buds while they can see them, and why farmers depend on rotation.



Tarnished plant bug - note damage in upper right corner of picture. Photo by Eric Sideman.
T
arnished Plant Bug: Tarnished plant bug activity is very low to non existent so far this year, but now is the time to get ready. Last year their population was bigger than I had ever seen it and they essentially wiped out all early pepper and eggplants for me. The tarnished plant bug is a small (6 mm), bronze, brown and black bug that feeds on a very wide variety of plants. They overwinter as adults under debris and become active early in the spring. There are three or more generations per season. They are serious pests on strawberries (causing cat faced berries), lettuce (browning of midrib), flowers (destroying buds), eggplant and pepper (destroying buds), broccoli (brown beads in the head), and much more. They are common on potatoes where they basically kill flowers (who cares?). But last year the numbers were so high the damage tof the leaflets was extensive enough to be confused by many growers with late blight.

Now is the time to be managing them on peppers and eggplants; before they arrive. If you want early peppers and eggplants, cover them with row covers and keep them on until you see good flowers. It is pretty easy to kill the bug with pyrethrum, but not worth it because their numbers are so great in all the fields of hay and weeds surrounding you that any you kill will be replaced in a day or two. Weed management and timing of mowing neighboring fields is about all you can do to keep the numbers low. Do not mow fields when you have host crops in sensitive stages, e.g., strawberries with buds.


Three-lined potato beetles. Photo by Eric Sideman.
Cucumber Beetles On My Potatoes?
No. Those are not cucumber beetles. Potatoes, tomatoes and sometimes eggplants are attacked by this pest that only superficially looks like a cucumber beetle. This is the THREE-LINED POTATO BEETLE. The adult of this pest is about the same size as a cucumber beetle but has a reddish head and a thorax with two dark spots. The wing covers are dark yellow with three black stripes. Its favorite food in my experience is tomatillo.

The Three-Lined Potato Beetle overwinters as an adult and wakes early in the spring. They are there waiting for you to plant your solanaceous crops. The females soon begin laying eggs that hatch in about two weeks to larvae that look a bit like Colorado potato beetle larvae, except these critters have the endearing practice of carrying a small pile of their own excrement on their back. The larvae mature in about two weeks. There are probably two generations per year.

On most crops the level of the pest does not warrant control. If this pest has been a problem in the past, floating row covers will help you avoid the overwintering adults and that should get you by. Hand picking will work on small plantings. Pyganic and Entrust may offer some relief. Rotenone works well, BUT REMEMBER THAT THERE ARE NO ROTENONE FORMULATIONS THAT MEET ORGANIC STANDARDS.


Pythium diseased pea plant.
Photo by Eric Sideman.
Pythium Diseases Of Peas:
There are several species of Pythium that cause pre and post emergent diseases that effect the seed (seed rots), seedling (damping off), and roots (root rots) of peas and beans. We are all familiar with damping off of seedlings caused by Pythium, but it can cause problems in older plants too. Once the plant emerges and develops mature cells with thicker cell walls, Pythium is less likely to be a problem, but it still may attack the young cells at the root tips and lead to “root pruning” and stunted, chlorotic plants. Pythium diseases of seeds and seedlings results in gaps in plantings where seeds have simply rotted away, or stunted seedlings simply died shortly after emerging. If your plants begin to yellow and are stunted, and the roots seem feeble, Pythium is a likely culprit. With this very wet early start to the year I am seeing some of this.

Close-up of roots of Pythium diseased pea. Note lack of young roots. Photo by Eric Sideman.
Pythium spp. are common soil inhabitants with a wide host range, which makes crop rotation less effective. The pathogen can survive for many years with no host at all in root debris as resistant spores or sporangia. High soil moisture is necessary for the disease to become a problem for peas or beans.

Anything you can do to get the soil to dry will help. In the future, avoid using old seed with low vigor. Deep plowing to bury root debris has been shown to reduce the disease in some studies. Avoid wet soils when you can.
Biological control agents may be useful as seed treatments. Actinovate AG (Streptomyces lydicus), MycoStop (Streptomyces griseoviridis), and T-22 HC (Trichoderma harzianum) are labeled for Pythium, but I have not yet heard about the efficacy of these.

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