Growing cucumbers is an almost impossible task lately because of the cucumber beetle problem here. The beetle harbors a bacterial wilt disease in its gut and infects the cucumber vines when it feeds on them. The actual damage done by the beetles is minimal, but their bite is the kiss of death to the vines if they are carrying bacterial wilt (Erwinia tracheiphila). Within a few days the vine starts drooping and eventually dies as the bacterial infection clogs up its vascular system. There is no cure except prevention, and that is difficult. The beetles are tiny and elusive, and they like to hang out inside of the cucumber flowers which makes them difficult to locate. I have not had success controlling them.
This year I am going to try something new and use a kaolin clay product, Surround WP. Surround is a finely ground white clay that is used to coat the leaves and stem of the plants you want to protect. It is not a pesticide but a deterrent to insect activity. It comes in a 25-pound bag and is mixed with water to form a slurry, which is either sprayed or used as a dip. Since I started my cucumbers inside in peat strips, I chose to dip the plants in a bucket of Surround for first application. Later on I will have to spray the plants to reapply it after a rain.
I used a small one gallon bucket to mix the slurry, adding water to the powder and stirring to get it wetted. I tried a stick at first but found my fingers were more effective. You want the slurry thin enough that it drips but does not run off the leaves.
When ready to plant, I took a peat strip, broke off the top edges so they will not stick out of the soil, and swirled the plant in the clay slurry.
Once the plant is reasonably coated, it is ready to put in the ground, looking like a white ghost. I wondered if the clay has a negative effect on the plant, but it apparently does not and has some advantages. The clay breathes and sunlight can get through so photosynthesis is not affected. At the same time, the clay prevents sunburn of new plants and reduces transplant shock.
Here is a row of newly planted Homemade Pickles, a pickling cucumber, looking quite ghostly.
The most difficult to plant were the Monika cukes above, a pickler from Poland. The plants were very compact so it was difficult to plant them without soil getting on and sticking to the wet clay.
Time will tell if this type of treatment works. UMass seems to think it does. It is important to start it at plant out because cucumbers are most susceptible when they are young (less than 5 sets of true leaves). Surround is widely used by commercial growers and both Johnnys and High Mowing Seeds use it in their fields. It is widely used in orchards and vineyards. And it is also useful for other plants and pests, such as flea beetles on eggplant, thrips on onions and squash vine borers and squash bugs, so I may apply it elsewhere in the garden, once I get a sprayer than can handle a wettable powder.