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Hemp Borer

Eurasian Hemp Borer is a voracious pest that will feed on various parts of cannabis plants for the duration of its life including stems, stalks, flowers, and seeds. Borers also have two mating seasons over the summer, which means they can either kill young plants before they can grow or ruin plant sites near to their harvest date. They are small, 6-8 millimeters, and will transition from beige to red-orange colored as they mature. Borers will hatch and immediately enter the plant at the stem of a leaf and these areas can be found by their excrement left at the entry point. When they are young, damage to stems is fairly minimal and will present as a slight bulge or discoloration. As borers age, they will migrate into main stalks and create bud-killing damage such as eating through the entire stalk or eating the interior to be hollow, shown by darkening of the stalk. During the second mating season, borers can be hatched on or near the bud site and can directly target seeds in the buds and feed on them.

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Prevention is the first step to ensuring these pests are not present in a crop from the start.

Ensure that all debris and over-wintering sites are removed in or near the growing area, leaves, and weeds being the biggest culprits.

It may also be helpful to rotate between growing sites outdoors to make sure that they are properly ploughed and cleaned of all debris as well as possibly treated with beneficial nematodes or insects.

Excluding the hemp borer moths from the site can prevent eggs from being laid, so using protective netting or promoting predatory birds or a night light trap is important. The eggs can also be targeted by using preventative treatments of parasitic wasps such as Trichogramma minutum or assassin bugs, this will reduce the amount of damage an infestation could cause if eggs are laid.

Another tactic may be the application of horticultural oil or pesticidal oil to coat and smother the eggs if other methods have proven to be unhelpful.