Detailed Instructions for Application of Habitat Herbicide to Kill Red Mangrove
Ann Kobsa, Malama O Puna, PO Box 1520, Pahoa, HI 96778 USA ann.kobsa@gmail.com
1. Drill/Inject Method
Any mangrove tree that is taller than 4 ft. should be drilled or broken. A trunk 5/8” or thicker can be drilled. A 7/16 or ½ inch augur bit works best, in a battery-powered drill. Drill at an angle of at least 45 o
from horizontal. Do not change the angle of the bit while drilling or breakage is likely. If possible, pull the bit from the hole without reversing, to remove the shavings from the hole. One hole is adequate for smaller trees, while a trunk of 6 inches diameter or greater should have 2 or more holes drilled on opposite sides of the trunk. When a tree is divided into several trunks low down, drill each one as if it were a separate tree. The dosage for Habitat is 0.1 milliliter per inch of diameter for trees 2 inches diameter or less, and 0.5 milliliter per inch of diameter for trees greater than 2 inches diameter. These dosages should kill every tree.
If a sapling is small enough to easily break, do so below the lowest leaves or branches and apply a drop of undiluted Habitat to the break, on the lower (rooted) portion. The drill can be used to encourage a break if it is too tough to break just by bending.
Measurement of herbicide is done by counting while squeezing a plastic squirt bottle (Fisher
Scientific, 250 ml, VCAT DS2420-0250). It is helpful to practice with water before going out in the field. Squirt into a measuring device while counting to “calibrate” your squeezing pressure so you dispense one milliliter of liquid per one second of squeezing.
Do not fill the drill holes all the way to the top as then herbicide will leak out and pollute the land/water. With practice you will learn how deep to drill for a given size tree, and until that happens, if you cannot fit the appropriate dosage of herbicide into your drill hole, drill an additional hole for the extra. With the smaller trees, be careful not to let the drill bit go clear through the tree, even the tip, or the herbicide will run out.
Mark the trunk of every drilled tree, using a paint stick (livestock marker, available at feed stores), with a single line all the way around the trunk, visible from all sides. This greatly facilitates thorough and efficient treatment.
Repeat Treatment: If it becomes necessary to redril l trees that did not die after the first treatment, it is very important to find a living portion of the tree to drill into. If a tree is drilled a second time into wood that is dead, it will continue to live because dead wood does not take up herbicide. You can tell if a portion of the trunk is alive by a thin layer of green cambium under the outer, brown skin, with pink inner bark, and pale pink wood. If it is dead you will see reddish-brown inner bark and tan wood.
Mangroves have prop roots that can connect branches 30 ft in the air to the ground. These can support a branch or trunk that is dead lower down. It is effective to drill and inject herbicide into these prop roots. Look to see which prop roots are feeding the living portion

of an “undead” tree and drill them. You can tell whether a prop root is alive as described above for a trunk. Put herbicide only in living prop roots. An alternative to drilling the prop roots is to climb up a tree with a dead lower trunk, in order to drill into the living portion of the trunk.
2. Foliar Spraying of Habitat on Red Mangrove
The shorter-stature mangroves are sprayed using backpack or hand-held sprayers containing
0.3 % Habitat, 0.3 % Can-Hance (or another methylated seed oil adjuvant) and a dye (we’ve used 0.2 % Mark It Red). Backpack sprayers are not made for rugged jungle use or bending over, so be careful not to spill on yourself by tilting the sprayer too much (which isn’t much at all when it’s full). Fill the tank with water and then add chemicals and shake to agitate.
For 15 liters, use 45 ml each of Habitat and Can-Hance, and 30 ml of dye.
Use low pressure and do not try to saturate the leaves. It is best to cover about 70% of the leaf surface with droplets, and avoid herbicide running and dripping off. Use an adjustable nozzle so that you can get a longer reach for taller mangroves or ones that are farther away, and a finer spray for closer ones. Avoid a spray that is so fine it drifts easily. When spraying thick stands, do not try to get every leaf as this is impossible. Additional rounds of spraying will be necessary after defoliation from the first round exposes the more interior leaves and plants.
Leaf loss will usually begin within one week of treatment, and will be complete within a few weeks. Habitat kills the propagules on a tree when the tree is killed by either injection or spraying. Habitat is inactivated as an herbicide when mixed with seawater, so do not try diluting in salt or brackish water.
Avoid spraying the native vegetation , which includes milo, hau, naupaka, hala, and akulekule (the low-growing succulent plant that looks like a portulaca). Do not attempt to spray if there is rain likely, as rain even a couple of hours after spraying prevents the herbicide from working. We like to be finished spraying by 3-4 pm, since rain often comes in the evening. Avoid spraying in wind that causes excessive drift. Usually if it is too windy to spray out in the open, conditions are just right for spraying in the interior regions. Work at low tide as much as possible for convenience and also to avoid contamination of the water and inactivation of the herbicide by the seawater.
Hawai‘i law requires that prior to any application of herbicide in an area where the public has access, such as the coastline, we must put up signs warning of the application. We must also verbally warn any people who are present. After reentry is permitted, which is as soon as the herbicide is dry, the signs may be taken down.
Even though Habitat is not a restricted chemical, Habitat application requires the applicator be certified by the state, however, in Hawai‘i, only one project member need be certified and that person need not even be present. All applicators are required to have detailed, written instructions from the certified applicator, hence this document.