Soil Mixes, Cactoblastis cactorum moth prevention and care

A few years ago I experimented and concocted a versatile, high performing and well-draining soil mix for the columnar cacti that I grow, and it has proven outstanding for my plants and those of my customers. The more water-loving, tropical columnar cacti, and even the big desert Pachycereus and barrel cacti, thrive in this mix despite excessive rain on potted plants and outdoor amended beds here in N. Florida. All of these ingredients plus pellet fertilizer can be found at Lowes.

Mix into a large rectangular plastic tub 1 bag Miracle Gro Cactus, Palm & Citrus garden soil (must say “moisture control” on bag), 1/2 bag Cowabunga compost with manure and 1.5 8-quart bags of Perlite. Break up clumps in the Miracle Gro soil using a coarse mesh sifter, or by hand, then mix with a shovel all of the ingredients until uniform. I use a thin layer of pea gravel to cover the dirt, in order to prevent soil from washing out and Perlite from floating to the top.

Dynamite brand pellet fertilizer added every six months has increased growth and height dramatically, and it is far less likely to burn plant bases that it touches. I order it from Walmart online.

For less frequent repotting in large vessels or outdoor raised cactus beds, though more expensive, adding 1/8″ black scoria and coarse Turface (Lesco All-Sport) to the mix will give it more permanent body and lessen settling from composting over time. I use Caribsea Eco Complete black aquarium gravel (lava) because of its off-the-charts micronutrient/rare earth element content.

Cactus Conservator’s Mix from Botanic Gardens – for cacti that grow on karst in the Caribbean and Florida Keys

When I visited Fairchild Tropical Botanic Garden and Montgomery Foundation some years ago, their native/endemic Florida cacti were growing beautifully in a mix that is more mineral, and thus more stable for a permanent large pot or display bed. Their Harrisia and Pilosocereus looked fantastic at large sizes and I used it with great results when up-potting large specimen native Florida species at Cactus Island. Here is that recipe:

“The mix I use for the cactus is a 1/3 standard potting mix, 1/3 crushed limestone, and 1/3 Turface. The Turface comes in 3 sizes. I use the coarsest grade (largest size) in the mix. For every 5 scoops of these components I add 1 scoop of organic soil for a little extra kick. The limestone provides the correct pH, the Turface provides the high CEC capacity (cation exchange capacity) and since it’s fortified with calcium clays, the appropriate pH, and the potting media to hold moisture. I use a time release fertilizer made specifically for growing in Florida, Nurticote 18-6-8, Florikan CRF 18-6-8, or Osmocote 18-6-10 as nutrition.“

Turface and crushed limestone of the same 1/8″-1/4″ grain size. Quickcrete or Sunniland crushed limestone (Lowes) is what I use, and it must be rinsed several times until water runs clear and not too much milky white. You’ll never get all of the white tint out of the water but three rinsings in a big rectangular sheet of windowscreen, inside a concrete mixing container, with agitation should do it. The coarse Turface (once-fired calcined clay) will help neutralize that.

Cactoblastis cactorum moth prevention recipe:

If you have Opuntia, Consolea and Cylindropuntia cactus species (prickly pear pad-type cactus), there is a species of South American moth that traveled across the border and along Gulf of Mexico states clear down to the Florida Keys, where it has seriously harmed those genera of cactus in their habitats. The moth lays an egg stick that looks like a ramen noodle on the tip of a needle, caterpillars hatch and drill into pads to hollow out. Pads or entire plants can be destroyed. I have had total success by combining two natural bacterial pesticides in a backpack sprayer: a heaping tablespoon of Dipel DF (Dry-Flowable BTK Baccillus thuringiensis ssp. kurstakii) and 1/8th of a small container of Monterrey Spinosad (also a bacterial agent, in liquid form) to 3-4 gallons of water for a backpack sprayer. I spray down all surfaces of pad cacti every 15 days between early March and November. Even with regular rain, the regular application at this interal breaks the insect cycle by killing eggs and hatched larvae that take their first bite into the cactus. The bacteria enters the gut of the caterpillar, crystallizes into sharp shards and kills them quickly. They’re safe for people and animals but one should wear a face mask to avoid inhalation. I buy both on eBay. If a species of parasitic wasp is approved for release in the wild, per U.S. state, Cactoblastis cactorum will become less prevalent, hopefully eliminating the need for this treatment.

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