Eric Sideman's Pest Report
June 29, 2001
This is the first pest report of the year and will be short For those of you who have not received pest reports I write them about once a week and tell what pests and diseases I have seen during my travels and on my farm and discuss a bit about the biology and control. I also want to start by thanking my other sources of information. A great deal comes from Ruth Hazzard who works in the IPM program at the University of Massachusetts and gave me permission to take what I want from her newsletter and adopt it for organic production. I also get news from Maine Extension folks including David Handley at Highmoore farm and all the folks at the pest management office. I want to hear from you too. Send me any updates on pest problems you have and I will include them in the next report.
Crop Condition
For the most part, vegetables are doing very well this year after a late start due to late snow melt. Peas are just coming in about a week late after being planted 2 weeks later. Lettuce and spinach harvest have been good.The soil is dry again in some parts of the state. It may be worth your while to go out and dig down a bit. Even though we have had a fair number of showers recently, the soil is soaking it up because it was so dry in April and May.
Potatoes
The Colorado potato beetle eggs are hatching and larvae are now widespread. Remember, the beetle over winters as an adult and the adults come awake in the spring and lay eggs. It is now time to spray with Bt San diego if you have small larvae feeding. The Bt works best on small larvae, only fair on larger larvae, and not at all on adults. If you wait they will get away from you. If you spray now, check the field again in a week and spray again only if you see new hatch. I have usually only had to spray twice a season.Lettuce
There are reports of a green caterpillar feeding on lettuce this year, which is not common. Ruth has had reports in Massachusetts too and she thinks it may be an alfalfa looper. In any case, no matter what it is, it is causing some really severe damage in some fields. If you need to control it the Bt for caterpillars will work.Broccoli and the family
The imported cabbage worm is here. Scout your fields and only spray Bt if you have the pest. Remember, Bt is only effective for about a day so there is not any point in spraying unless you have the pest to kill.The cabbage maggot has come and gone so you can take your covers off if you were protecting crops from it.
Ruth reports that in Massachusetts Club root has been observed in some fields of crucifers. This is a very destructive root disease caused by the fungus Plasmodiophora brassicae, which can persist for long periods in the soil. It attacks all species of brassicas. Plants are more likely to be adversely affected in low pH soils with adequate or high moisture. Long crop rotations help reduce the populations of the pathogen; however, once it is present it is difficult to eradicate. Raising pH to 7.2 is the most cost-effective way to manage the disease, if infected fields continue to be used for crucifer production.
Plants can be infected for some time before showing symptoms. The first aboveground symptoms are usually wilting during midday heat. Roots of infected plants become enlarged into various shapes, and uptake of water and nutrients is reduced. Both transplants and direct-seeded crops can be infected.
Corn
There are reports of common army worm in grassy fields doing lots of damage. That means it may move into corn fields. Keep your eyes open for ragged leaves. Bt will work well for this pest.Squash family
Cucumber beetles are present at low levels in some fields, but growth has outstripped the need for concern about feeding damage so far. Beetles are attracted to blossoms (along with bees), but do little damage. Beetles do need to be controlled in wilt-susceptible crops such as melons and cucumbers. Keep your eyes open in case numbers go up.Leaf hoppers
Watch fields for potato leafhopper. Field reports are variable ? In Massachusetts some fields show low levels, others are significant. I have not seen it here in Maine yet.Adults are about ¼ inch long, light yellow-green, and fly up from foliage when it is disturbed or shaken. They can also be monitored with sweep nets. Nymphs are found on the underside of leaves, light green, wedge-shaped and very fast-moving. Damage can be severe on early-season varieties of potato and beans. Some late-season varieties such as Katahdin seem to have more tolerance. Adults and nymphs feed by inserting a needle-like beak into the plant and sucking out sap. They also inject a toxin into the plant, which causes yellowing, browning, and curling of leaves. In potato, leaf margins turn brown and brittle first, followed by death of entire leaves. In beans, the leaf turns mottled brown as if . Both adults and nymphs cause damage. Plant injury and yield loss can be significant.
The best control that I know is the concentrated pyrethrum sprays such as Pyronyl that Johnny's sells.