Common Hemp Crop Pests
Aphids are found on the bottom of leaves and/or stems and they can can grow into large colonies. They tend to have a mouthpiece that sucks away by puncturing the plant tissue and digging away at the sap. In doing so, the leaves start to turn yellow and become dry.
In some cases, there will be droppings that are going to appear, which can lead to different diseases. To avoid this issue, it's best to keep everything as clean as possible around the area.
With the Bertha Armyworm, most of the damage is done by the larvae as they feed on hemp. As the winter months come around, Bertha Armyworms tend to remain in the soil. However, it is sometime in the middle of the grow when the moths start to appear and lay eggs close to the plan. They want to have the eggs near these plants, so the larvae can feed on the host plant. This ends up damaging the hemp over time. When the larvae mature, they'll continue to go through their life cycle.
Depending on how cold the winters are, their populations will generally remain on the lower end. Hemp can withstand a large number of Bertha Armyworms without breaking down but additional studies have to be done on this particular issue.
A variety of birds tend to fly near hemp crops and these can include blackbirds, doves, sparrows, and starlings to name a few. As soon as the hemp begins to harvest, these birds will start flocking in the area and can do some bit of damage to the crop. This has a lot to do with them needing food and they will also want a place to perch. Most studies show these birds prefer staying close to the hemp field as it is easy to get at the seeds when they are looking to eat.
Birds will also leave droppings on the hemp head during the feeding process, which can contaminate the plant. This becomes a problem when the hemp grain isn't regulated. The contaminants can vary including molds and even E.coil or Staphylococcus.
With cutworms, hemp production tends to get hampered in certain regions during the spring. This is a spring pest, so the cutworms' activity level goes through the roof during this period. They tend to remain in small subsections of the field rather than covering every inch.
Deer may be seen around hemp as they look to feed or graze in the area. They will only go for the top part of the plant without compromising the root. As a result, the stalk can branch and produce a plant that has multiple stalks. They might be smaller in size but they can still be manageable when it is time to harvest.
European Corn Borer
With the European Corn Borer, the level of impact on hemp depends on how close it is grown to corn. The corn borer tends to change to a pupa in the spring, which is when the conditions improve. As it turns into a moth during the end of May, additional eggs are laid around hemp. The moth looks for the right plant host and hemp tends to be one. This is when damage is done to the hemp because the larva goes through the hemp stalk and feeds in the middle. This can have a serious impact on the hemp stalk and how it grows.
Grasshoppers have been seen in certain areas, especially where grasshopper populations are common such as dry regions. If crops are grown in those areas, grasshoppers can have an impact on the crop and how well it grows. In most cases, the crop tends to outgrow any signs of infestation. Most grasshoppers focus their attention on the outside leaves. If there is a higher number of grasshoppers present then this can lead to the bract getting damaged during the development phase of the seed. This is when the crop is hampered and the yield is impacted. It's important to keep an eye out for this along the edges.
On average, grasshoppers can end up eating around 30-100 mg of plant material per day. It's important to note a grasshopper's life cycle begins during the autumn months as the female deposits eggs in an egg pod. As soon as the embryos start developing later in the winter/spring, the hatching starts around may. This is when nymphs are produced (grasshoppers minus the wings). These nymphs will go through several growth stages before turning into adult grasshoppers. Once they have wings, they can fly around and cover quite a bit of ground. This is when they do the most damage.
Lygus Plant Bugs
With Lygus Plant Bugs, they tend to be seen around the vegetable, canola, and alfalfa crops. They will look to suck at the hemp by puncturing the plant. When there are higher numbers around, they can do quite a bit of damage to the bracts. Since they tend to puncture the plant using their mouthpiece, it can also lead to diseases such as Aster Yellows.
These are known for having a shield and will often keep other insects away. However, they will also look to get to the sap in the leaves by piercing the plant tissues. They will also excrete the sap which can lead to fungus such as sooty mold. When this happens, it is important to remove the affected part as soon as possible.
Stink bugs are known to have a particular smell to them and can be seen in hemp fields as harvest season approaches. They will begin to suck away at the plant looking for juice, which can damage the hemp seed head. This has a major impact on the bracts, which ensures the seeds don't develop as well as they need to. However, stink bugs tend to remain focused on certain areas of the field.