Grapholita delineana infestation can lead to catastrophic crop losses
The European hemp moth, also known as “hemp moth“, Is a very destructive pest that frustrates many hemp growers in the United States. Given the high number of farmers who cultivate hemp for CBD oil, food products or cosmetics, it is necessary to find natural solutions to the hemp moth problem and a low-tech approach is often the best. Many chemical pesticides, which may be available to industrial hemp and fiber producers, are unsuitable for consumer goods like CBD oils and cooking oils.
Natural solutions to the hemp moth problem: Grapholita delineana
The U.S. Environmental Protection Agency (EPA) approved ten additional pesticides suitable for hemp in late 2019. But unfortunately, it's not clear exactly how they appear after extraction.
Since there is zero tolerance for pesticide residues after treatment, a process that naturally concentrates everything on or in the raw material is a risk.
Crop failure due to corn borer infestation, and post-harvest rejection due to pesticide contamination, are risks that no grower is prepared to take. For farmers of hemp for consumables, natural and preventive measures are the only safe and viable means of solving the problem of the hemp moth. Growing hemp continues to require a significant initial investment to get started.
About the European hemp weevil
The hemp moth (Grapholita delineana) is technically the caterpillar (immature) stage of the hemp moth. According to Center for Agriculture and Bioscience International (CABI), it is spreading in Europe, Asia and North America. In the United States, the corn borer is widespread in Illinois and most of the producing states. Others reports indicate that it is also widespread in eastern Colorado.
Hemp moths are small white caterpillars less than one centimeter in size. They have a dark black dot, and as they grow their bodies take on a red-orange tint. The larvae of the hemp moth cause significant damage when they pierce the base of the hemp flower. When they enter the flower, it wilts and eventually dies.
Therefore, the hemp moth can additionally cause stunted and deformed growth along stems and branches. So this is a serious problem for farmers who cultivate CBD strains. And also a concern for those who produce fiber.
The larvae of the hemp moth
Although an infestation may not become apparent until after harvest. Especially when the caterpillars dislodge from the flowers during the drying process. They move technically in the weeks preceding the harvest. Left unchecked, larvae overwinter in stems and seed heads. In mid-spring, and at the end of pupation, moths emerge to mate. During the growing season, hemp moths can experience up to three regenerations, which end with the cooler fall season.
Natural solutions to the problem of the hemp moth
early prevention : Hemp growers should monitor crops from year to year for signs of possible hemp moth infestation. Even if the caterpillars have little or no damage to the flowers in the current year, careful assessment is necessary to avoid an explosion the following year.
During harvesting, drying, and other processing operations, watch the flowers for signs of larvae. Since they can come loose during handling, keep a close eye on machinery, floors, and other surfaces that collect debris from processing the hemp raw material.
As caterpillars overwinter inside plants, growers should remove all seed heads and flowers from the field. Most harvesting machines cut plants at the base of the stem and leave little material behind. This step is therefore generally easy to perform.
The state of Colorado recommends locating processing plants at least ½ miles from grow sites. This distance will reduce the risk of borers surviving on drying room floors, metamorphosing and infesting local fields the following year.
It is also believed that hemp borers could survive in several localized weeds that grow around and inside hemp fields. Growers would be well advised to mow all weeds before planting and again at harvest to ensure that there is no survival in the fields during the winter.
Continuous crop monitoring
Since the hemp moth goes through several generations in a single season, continuous field monitoring can help detect the problem long before the larvae begin to make their way through the flowers and seed heads.
According to the state of Colorado, in general, infestations start at the edge of a field because moths are poor pilots able to travel short distances. Regular inspection of field edges for butterfly activity and subsequent destruction of any infested plants could limit the spread.
And while pheromone traps aren't effective for monitoring hemp moths, sweeping nets are of some help. Regular testing of broomnets collects samples of the current insect population and captures the hemp moth long before it infiltrates further.
Are there safe pesticides?
Unfortunately, hemp moths are a difficult pest to target, even with conventional pesticides. As the caterpillar lives inside stems, stems and flowers, sprayed pesticides often don't do much damage. Even though these pesticides get inside the flowers, they are not suitable for most growers working with cultivars intended for the CBD market.
Again, the EPA recently approved ten additional pesticides for hemp. A total of nine of these chemicals are bio-pesticides, including varieties of Bacillus thuringiensis, that is, products derived from natural sources. Bacillus-type pesticides are pathogens harmful to insects such as the hemp moth.
Are these bio-pesticides harmful to humans? Most research indicates no, but again, it is unknown how the CBD extraction process affects this pesticide. Additionally, if a hemp flower is intended for a final smokable or ready-to-smoke (flower and hemp oils) form, there is absolutely no safety information available.
Essential preventive measures to naturally fight against the moth
The safest and cheapest way to control the hemp moth infestation is to tackle the problems as they appear at harvest time. These are low tech solutions, but so far this is the only proven way. Stopping the caterpillar's life cycle between seasons is efficient and simple. Combined with continuous field checks in the spring and summer, post-harvest cleaning will detect localized infestations if they occur.
The habits of the hemp moth can protect it from chemical spraying (natural or not), so that the hemp grower is best served by preventive measures and continuous monitoring of the crops.