I grew watermelons and cantelopes in Austin, Texas for several seasons. They always had a decent set inspite of 100 plus degree days forever (Think 60 straight days or more) and really high night time temps. In fact I used to get bored in mid summer and start a second round of melons in July. That being said if your hundred degree days have come on all of a sudden then it may well have your plants in a bit of shock. My guess is however that if your vines are healthy as soon as your heat wave breaks a little your vines will start to set. Hopefully it wont be too late for a harvest.

Thanks,
Scape

Could be a soil chemistry issue, maybe brought on by the heat. Ca/Mg balance might be worth investigating since you mentioned you're applying Magnesium sulfate which you had not in the past. Too much fertilizing could be a problem if the plants are at all drought-stressed.

You might be on to something with the idea of "this soil" in "this heat."

The rates at which I have added the epsom salt is so low that it would be hard to imagine over-fertilizing. I've gone through only about a pound in the course of a month, which doesn't seem like much for 1,500 feet of melons. The ground did receive a broadcast granular fertilizer before we planted, but I looked it up and the rate we apply is much less than what I read is standard.

I don't have blossom end rot, thankfully. The flowers just dry up and drop off without growing a melon. I do have some Calcium Nitrate that I could feed through the drip line if it might help.

The soil is a mostly un-amended, light-colored clay. The only organic matter it gets it from letting the grass grow over it and tilling it in the next year. In the past, it was always fine. I wonder if the intense heat might be making the difference, and exposing the weaknesses of our unamended clay? There are some volunteer gourds that have come up in our adjacent patch or dying corn, and they look a lot worse due to not being irrigated. I don't see any gourds on them, either.

For next year, I am wondering if manure in the soil might help. I could also switch from black plastic to the white-on-black kind that is white on top and keeps the soil from warming so much.

It's not from the soil or air being too hot, melons love hot weather. Above 100F is not ideal for long periods but 90s are fine.

However melons don't pollinate well in hot dry windy conditions. And they must have bees for pollination. They only pollinate well right after sunrise in morning just after the flowers open. Wind and low humidity in early morning cause the pollen to dry up on the male flowers and the bees are less effective. I've found this out the hard way, by hand pollinating for many years.

Thanks. I have never seen the humidity this low. Normally, we have a heat index that is 10-20 degrees greater than the temperature. This year, the heat index has been typically lower than the actual temp, which I did not even realize was possible.

If I dragged a hose out and sprayed the plants late at night or just before dawn, would that help? Or would I just unproductively blast pollen everywhere??? It would of course go against the common wisdom that spraying water on leaves is a bad thing. I'm fine with spraying Daconil or other fungicide if I had to.

I have not checked on my beehive, but with the drought, it would seem like bees would be all over whatever flowers they can find. The catnip blooming in my front yard is full of bumble bees.

Robbie:

Spraying water won't do anything to pollinate. The male and female flowers are too far apart. There is nothing other than bees, or perhaps some other insect, to pollinate that many melons. Why not check your hive. Bring in another if possible. Each flower needs multiple visits for best pollination.

Last year we had humidity below 1% some afternoons, 15-20% first thing in the morning. I had real difficulty getting fruit set even by hand. This year on the good mornings I had too much set. The hail took care of that. But early morning weather makes a huge difference.

Thanks for the help. I am not looking forward to learning how to be a bee keeper. After I got stung, I read a little on the beekeeper forums. The drought seems to have caused a "nectar dearth," which made hives raid each other, which made the bees so defensive that they stung anyone walking near the hive.