Summer pests and diseases

Hornworm on a tomato plant.
Photo Pam Dawling

It’s August, which for us is the peak time for pest insects as well as for fungal diseases.

This year, we have been collecting Japanese beetles from our okra plants, to prevent the leaves getting stripped off. It seems to be working. Many plants can take 30% defoliation without a loss of yield, but some years, our okra plants end up as just a bunch of stalks, and you know that means almost no photosynthesis can happen. Japanese beetles are one of the insects that have an aggregation pheromone, so those commercial traps are not only gathering up your own Japanese beetles, but also attracting neighbors’ beetles. Sometimes this means no net improvement, as the newcomers eat crops before going into the trap.

Another bad summer pest here is the Harlequin bug, a brightly colored stink bug. We try to have July be “No Visible Brassicas Month” aiming to disrupt their lifecycle. We use insect netting over the fall brassica seedlings we sow in June, and we clear our spring brassicas before the end of June. In July and July we use netting over any new brassica transplants, and sowings of turnips. During August we remove netting from older transplants and sowings, on to newer ones, such as kale and collards.

Leaf-footed bug, one of the stink bugs. Photo Kati Falger

Here’s a link to an article on Stink Bug Identification and Management in Vegetables, from the Alabama IPN Communicator Newsletter. Read More

I wrote about squash bugs and cucumber beetles on our hoophouse squash in June.

Squash bug nymphs and eggs
Photo Pam Dawling

Margaret Roach at A Way to Garden has a good post on distinguishing between the tobacco and the tomato hornworm.

The tobacco hornworms, Manduca sexta, is close cousins with the tomato hornworm,

Both species eat Solanaceous crops (nightshades) such as tobacco, tomato, peppers, eggplant and potatoes. The differences are in the stripes and the horns.

We have tobacco hornworms (this land was a tobacco farm before Twin Oaks bought it 51 years ago. This year, for the first time, we haven’t had any hornworms in the hoophouse. We’ve pulled up our tomato plants in there – we only grow the earlies in there, as it’s plenty warm enough to grow tomatoes outdoors here from May to October. I might be celebrating too soon – we still have a bed of peppers in the hoophouse and I think I might have seen evidence of a hornworm at work, although I could not find the culprit yesterday.

Tomato plant badly damaged by hornworm
Photo Pam Dawling

Pictures of Tomato Spotted Wilt Virus and other tomato diseases

We’re always a bit anxious that TSWV might show up one day, but luckily it hasn’t. Meanwhile we forget what it looks like. Here’s a few photos on the Cornell Vegetable MD Online site.

And here’s a good collection of tomato disease photos on the You Should grow site.

Spotty tomato leaves. I think this is Septoria Leaf Spot.
Photo Pam Dawling

All the news is not bad! Here’s a satisfying photo:

Hornworm mother Hawk Moth trapped by a zipper spider.
Photo Pam Dawling

Zipper spider.
Photo Wren Vile

 

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