Dealing with cut worms, the biggest danger to young trees

We are in the middle of the long rains season, a perfect time to invest in trees because the level of care, especially with regard to watering, is drastically reduced. Yet there are still challenges that tree planters are grappling with and seeking answers.

One of my readers, Duncan Wangete, wrote last week:

“I planted 1,000 eucalyptus trees in Webuye last month. I am sad to say that 281 trees have been eaten by cutworms. What are cutworms and how do I eradicate them completely?’’

Eucalyptus are not the only trees that suffer this damage. Many other young trees are vulnerable to these destructive insects.

In Soy, I have faced this problem with Whistling pines (casuarina), especially when still in the bed and in the early stages of potting and planting.

Cutworms can also cause a lot of damage to crops, especially vegetables and grass in lawns. They are a big concern even for those with small urban gardens.

Cutworms are the larvae (in caterpillar form) of night-flying moths. While the moths themselves do no harm to crops, the larvae destroy young plants by eating the stems at or near ground level.

When the moths’ eggs hatch, the larvae spend three to five weeks chewing on plants in preparation for the pupal stage.

They burrow into the soil to pupate, emerging as moths after, which they will lay eggs on plant stems and soil. The eggs hatch and the vicious cycle starts all over again.

According to Old Farmers’ Almanac, cutworms feed on roots and foliage of young plants, and will even cut off the plant from underneath the soil. Even if only the bottom of the plant is destroyed, the top will often shrivel and die.
Control

There are a number of ways to control cutworms, but the best one is prevention.

They are usually worse in areas that have not been tilled. Ploughing or cultivating the soil well before you plant your trees or other crops is a big help.

This is because the larvae hiding in the soil die when exposed to the sun. They are also eaten by birds and other natural predators that include ants and frogs.

SPRAY IN THE EVENING

Weeding is another method that prevents cutworm infestation. It should be done to remove dead plant material since the eggs that hatch into cutworms are laid on it. Weeds and other plant material also attract rodents, destroy trees.

The rodents will nest in the dirt, weeds and grass, from which they emerge at night to feed on young trees. I have had this problem with Acacia xanthophloea seedlings in Soy, Eldoret.

Those with gardens in urban areas can protects their crops by making collars. These can be pieces of cardboard around each plant stem to stop cutworms from reaching tender stems.

You can also save toilet paper tubes, cut them in half, fill with potting soil, and plant seeds in them. When young plants are ready, plant them in the tubes.

Prevention should be followed up with careful monitoring. The earlier you discover the pests, the easier it will be to control them.

One method, again for small gardens, is hand-picking the pests. They normally come out in the evening to feed and with a torch you can pick them and place them in soapy water, which kills them.

Even during the day, you can get to them if you dig around the stem of plants that are affected.

Natural predators

Amphibians, birds and other insects eat cutworms or their larvae.

Fireflies, which are also known as lightning bugs because of the light they produce at night to attract mates or prey, are also a natural predator to cutworms.

But all these methods may not be helpful if you have an acre or more of trees under attack. This is where chemical control comes in.

You can use chemical pesticides to kill cutworm pests. There are a number of pesticides that are effective against the insects. They are available in agrovet shops, from where you should seek expert advice on their application.

Generally, you should spray in the evening when the cutworms come out of their hiding places for feeding.

Another important reason for spraying in the evening is so that you do not harm useful insects that are active in the day such as bees and butterflies. Unlike moths, they play an important role in food production through pollination.