Milkweed plants need to be watered daily in the summer sun of Southern California.
If not watered, they will droop in 24 hrs, and die in 48 hrs.
Yellow leaves on the milkweed
I’ll get to the causes in a minute, but more importantly: here is the cure for yellow leaves:
trim the wilkweed back somewhat, and give it some water.
Yellow leaves in the LOWER parts is a sure sign that the milkweed has matured and is deleting itself.
Yellow leaves in the LOWER parts of the milkweed plant is NOT a sign of overwatering.
Yellow leaves in the LOWER parts of the milkweed plant is NOT some kind of plant virus or disease.
Don’t bother removing the yellow leaves from the LOWER parts of the milkweed, they are about to fall off anyway.
Yellow leaves ALL OVER the milkweed can be due to aphids, which are sucking fluid out of the plant.
Yellow leaves ALL OVER the milkweed, along with drooping, are signs that the plant needs water.
When tachnid larva emerge from a dead caterpillar, they will attempt to burrow into the soil or hide under a pot or rock. Once hidden, the tachnid larva will turn into a reddish-brown coffee-bean pupa, from which a tachnid fly will emerge in about five days. Even one tachnid fly could destroy all the caterpillars in your refuge cage.
Don’t give tachnid larva any where to hide in your refuge cage!!
In addition, keep your refuge cage uncluttered so the tachnid larva have nowhere to hide.
Look for tachnid flies on flat white surfaces, at the edge of shadow and light. They seem to be attracted by a sprinkle of water on a white surface.
Caterpillars oftentimes rest on vertical surfaces, like on the sides of the mesh cages.
They are molting, so just leave them alone.
In this phase, they are vulnerable to attack from all sorts of predators, so protect them in a refuge cage.
When you see a caterpillar in a vertical position, take it to your refuge cage
Do a patrol of your milkweeds early in the morning, looking for little caterpillars on the milkweeds. Any caterpillar that is on a milkweed that is out in the open needs to be taken to your refuge cage. If you rescue the caterpillars early in the morning, the tachnid flies will not have had chance to strike them. Tachnids don’t fly at night, and it takes them a while to get started in the morning.
In the wild, when caterpillars are large enough, they crawl down off the milkweed plant and try to make it to the base of a vertical object, like a fence or tree. From there, they crawl up the vertical object, hoping to reach the underside of a ledge or leaf, to which they attempt to attach. Once they have cast their anchoring silk on the underside of the object, they turn into a hanging J, from which they become a chrysalis.
During the large caterpillar’s journey, if it gets on a big, featureless wall, it will just wander up and down. The large caterpillars are not able to maintain their orientation on a blank vertical surface. If you see a large caterpillar on a wall, just take it to the refuge cage. The inside aspect of the top of the refuge cage is a perfect spot for the large caterpillar to turn into a chrysalis.
Buy and use cages to protect your caterpillars. The best kind will have a fine mesh screen. Get cages that have a flexible cable framework, which act like the fold-up sunscreens used in front windows of cars. A cage with fine mesh screening and a flexible cable framework will take literally 3 seconds to set up. DON’T rig up a do-it-yourself version of a cage: you will waste a lot of time, lose a lot of caterpillars, and expend much more effort than you needed to.
The best environment for developing Monarchs is this: milkweed plants, in their original pots, placed in fine-mesh-flexible-frame cage. Please just accept this advice, since it is the product of many hours of trial-and-error.
The refuge cage protects the caterpillars from the tachnid flies. Out in the open, the caterpillars have little defense against the tachnids. Once a caterpillar is stung by a tachnid fly, it is doomed.
The refuge cage also protects caterpillars against multiple garden enemies, such as ants, lizards, praying mantii, and birds.
Another benefit of the refuge cage is that it keeps the growing caterpillars in a confined space, so that, if they fall off the milkweed plants, they can easily get back onto the milkweed plants. Out in the open, if a caterpillar falls off a milkweed, it will wander off looking for another milkweed plant to climb onto, but oftentimes the caterpillar will get lost. On the other hand, if a caterpillar falls off a milkweed plant in the refuge cage, the caterpillar can easily climb up the pot and back onto a milkweed plant.
The inside of the top of the refuge cage provides a great spot for the full-grown caterpillars to attach to when they decide to turn into a chrysalis. In the wild, the full-grown caterpillars will leave the milkweed plant and crawl up to 40 feet away, then crawl up onto a structure or plant to find a place to turn into a chrysalis. This journey makes them very vulnerable to attack by multiple adversaries.
Another benefit of the refuge cage is that it protects newly-emerged female Monarchs from overly-aggressive male suitors. The newly-emerged female Monarch needs several hours to deploy her wings. If she is disturbed during this phase, her wings will not fully expand, her wings will remain crinkled, and she will never be able to fly. The casual observer might surmise that the female Monarch butterfly with crinkled wings is a victim of OEM virus, while in fact she is the victim of an overly-aggressive male suitor.
Still another benefit of the refuge cage is that it can be configured to protect developing Monarchs from heat. In Southern California the summer heat can be intense. Developing Monarchs do not tolerate temperatures over 90 degrees Fahrenheit. They become dehydrated, turn dark, and die. The refuge cage can be easily protected from the summer sunlight: get a swath of sunscreen cloth, fashion it into a cap, and place it over the outside of the top of the refuge cage. Use ziplock ties to attach the sunscreen to the outside of the top of the refuge cage.
You will need a vacuum cleaner to vacuum up the caterpillar droppings that accumulate on the bottom of the refuge cage.
NEVER use a vacuum cleaner while you are wet or standing on a wet surface.
If the refuge cage is full of milkweed plants in pots, DON’T drag it to a new location. The dragging causes rips in the undersurface of the cage.