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Eric Sideman's Pest Report

July 21, 2001

First I want to start with two announcements and an apology:

1) MOFGA is having a series of Twilight Organic Farm meetings this summer that you all should know about already, but just in case...the first one is Sunday (tomorrow), July 22, 2001 on growing onions. It will be at Jason and Barbara Kafka's. Call them for directions (277 3114). Click here for the rest of the schedule.

2) MOFGA will be hosting Small Farm Field Day with Extension at our site in Unity. It will be August 12, and the schedule will be available on the web soon.

The crops I have seen are growing very well this year. Some places are still dry and you know who you are and should get some water out there because there is none forecast to fall from the sky soon. It has been cool so some warm weather crops are a bit behind schedule, but I have seen most early summer vegetables making it to market. There was a long period of cloudy, cool damp weather and I would not be surprised to see some diseases popping up. Be on the look out.

LEAF HOPPER
(POTATOES AND BEANS)

I have received a few more reports of potato leaf hoppers. The numbers are very small so far and it is not clear whether sprays are called for. The threshold is one nymph per leaf or one adult per sweep with a bug net...very low. See last week's report (above) for more info and keep your eyes open and get me a note if you see them.

ARMYWORM
(GRASS AND SMALL GRAIN AND CORN)

Most sites are reporting them gone or nearly so. Now, keep your eyes open for the second generation. It is not supposed to be a problem, but I want to get at them earlier if we are wrong and it is a problem. So, scout your grass and small grains. IMPORTANT, the young larvae of the armyworm is different from the older ones (the first and second instar vs the third and forth). When young, the caterpillar is lighter green and more like an inch worm than an armyworm, which we all know by now is a dark green to gray with yellow stripe. The young ones do not have prominent stripes. But I think the numbers would give them away as armyworms.

TARNISHED PLANT BUG
(BROCCOLI and peppers and eggplant, see last week)

This is really bad this year in broccoli. What you see is the browning of the beads in the head just as it is sizing up. I do not have a great control and would love a tip if anyone out there has one. Row covers will work. Pyrethrum will kill the ones that are there at the time you spray, but I bet new ones will be there by the next day so it is probably not worth it. Any help out there?

BLOSSOM END ROT
(SUMMER SQUASH, TOMATOES, PEPPERS)

This is a physiological disease brought on by a calcium deficiency, but more often is actually due to the calcium that is in the soil being unavailable to the plant because, 1) too much water washes it away, 2) too little water means the plant has no way to pick it up from the soil, 3) high levels of ammonium can inhibit Ca (and Mg and K) uptake. Ammonium is a problem for conventional growers using ammonium types of nitrogen fertilizers or urea, but for organic growers it may occur if high nitrogen fertilizers (like blood meal) are used and then the soil becomes anaerobic because it is too wet. This may leave the N in the soil in the ammonium form. Blossom end rot especially occurs if calcium is limiting during fruit development. The most common cause is it is too dry during fruit set.

TOMATO

Early blight, Septoria leaf spot and bacterial canker have been observed in tomatoes. Early blight develops on older or inner leaves first; symptoms include rounded brown lesions on leaves that have a target-like ringed appearance. Bacterial canker very rarely produces leaf spots, but always has brown scorching or "burning" of the leaf margins. A yellow halo or margin may be present in either disease. In later stages of bacterial canker, when bacteria have invaded the vascular system, symptoms include wilting or death of one side of a compound leaf. Fruit will show small white spots with dark, raised centers. Another disease that may show up at this time (especially in unsprayed tomato) is Septoria leaf spot, which begins on lower leaves with small circular spots that have tan to gray centers and dark brown margins. Lesions remain small, up to 2.5mm in diameter. At their center, tiny black dots - fruiting bodies - can be seen. These are not present with early blight. It can be difficult to identify these diseases from foliar symptoms - if you want to know for sure what disease you have, contact the Pest Management Office (1800 287 0279). Where canker or other bacterial diseases are present, weekly applications of copper are recommended. For early blight crop rotation works if you keep tomato family crops out for two to three years. If you put diseased plants into your compost pile either do not use that compost with tomato family crops or make sure the compost gets hot. Picking off the lower leaves if they become infected helps. Bordeaux sprays will work well but may stunt the plant and reduce yield.