Growers Guide: Diseases and Pests to Look For When Growing Hemp

Hemp Farm Pest and Disease Management

Since the passage of the farm bill, there has been a hemp boom In the United States, with farmers from all over the country purchasing wholesale hemp seeds, and cashing in on the crop to make CBD bulk isolate, CBD hemp oil and more. As the plant started to grow more widely across the country, farmers detected increasing amounts of pests and diseases. Some of these pests, like corn earworm, are no stranger to industrial farmers, as they affect other commercial crops. Regardless, these pests are still nuisances and are best controlled with an integrated pest management strategy.

Just like most things in life, the first step to making a change is acknowledging the problem. In this case, it’s identifying bugs, diseases, and other issues that negatively affect your hemp crop.

Without further ado, here some issues to look out for while growing hemp so you can prepare.

Hemp Plant Pests

Corn Earworm

According to researchers at Colorado State University, Corn Earworm holds the most potential for damage. When it comes to hemp, corn earworms are public enemy number one. This worm is widespread across the United States and has a few different monikers besides corn earworm. It’s also known as the tomato fruitworm and the bollworm.

You may be relieved to hear that the worm typically poses a threat to plants that produce large flowers rather than seed or fiber varieties, as the majority of the damage occurs when the insects tunnel into buds and developing seeds. In places with milder winters, the pupas can survive in the soil and remerge the following season.

Hemp Russet Mite

Hemp Russet Mites can very easily go unnoticed, as they are basically microscopic. Often times, farmers don’t notice an infestation until they notice a powdery substance on the plant. This can easily be mistaken for mold or pollen but in actuality, it’s thousands of tiny bugs. Some early signs of infestation include curling, discolored leaves as well as brittle foliage.

Russet Mite infestations have been reported in California, Oregon, Colorado, Washington, Kentucky, as well as Tennessee, suggesting that this pest can be found nationwide. Additionally, the pest affects both indoor and outdoor grows. Some have even had to completely destroy their fields due to the severity of infestation.

Cannabis Aphid

Aphids are basically hemp vampires but instead of blood they drink sap. While there are a number of aphid species around the world that affect a variety of plants, cannabis aphids are only known to live on– you guessed it– cannabis.

Aphids can typically be found on leaves and stems where they feed. Unlike thrips or spider mites, aphids don’t leave visible damage, making them significantly harder to detect. However, as they feed, aphids secrete a sticky fluid called honeydew, which can make the plant more susceptible to mold. This fluid appears as shiny dots on leaves, signaling the presence of aphids.  Farmers can also look for “cast skins” or the shedded exoskeleton of the insects to determine if they have an infestation.

Eurasian Hemp Borer

The Eurasian hemp borer is actually a moth in its caterpillar (larval) stage. Currently, the caterpillar is only known to live in places east of the Rocky Mountains.

Hemp borers cause damage by tunneling into the base of developing buds, which then causes the stem to wilt and die. Farmers have also reported damage to developing seed. The insect can survive through the winter as larva within stems and emerge to repopulate during the next season. Currently, there are no pheromone traps that will catch Eurasian Hemp Borers so the best way to detect their presence is either visually or with a sweep net.

Hemp Plant Diseases

Powdery Mildew

Due to higher humidity levels, powdery mildew primarily affects hemp grown in indoors. It is characterized by a fine white, tan, or gray powder on the surface of the plants. This powder signals fungal growth on the plant.

Powdery mildew doesn’t love high heat, favoring temperatures between 60 and 70 ºF. While the disease won’t kill the plant completely. It can negatively affect flowering, plant vigor, and yields.

Leaf Septoria

Leaf Septoria also known as yellow leaf spot is a harsh disease that affects the foliage of many plants. The disease is caused by the fungus Septoria lycopersici and is characterized by yellow and brown spots forming on the leaves. It rarely spreads to fruits so it is unlikely that flowers are affected.

Leaf Septoria proves prevalent in regions affected by periods of wet, humid conditions. With this in mind, farmers in the North Eastern and South Eastern United States should be particularly diligent about inspecting hemp leaves.

Industrial Hemp Farming Plant and Diseases Plan

The above represents only a few of the pests and diseases that can affect hemp crops around the United States. Even mice have been known to cause disasters if seeds are left in areas and containers that they can access. As the crop spreads further across the country, we can expect to see an increase in pests and diseases. Have no fear, though. With increased knowledge, we will be able to create superior pest and disease management strategies. We are excited to see what creepy crawlies make themselves known this season! Keep in touch with us on social for the most up to date information @blueforestfarms.