They can be controlled by handpicking them off when their numbers are low . When that is not practical , they can be sprayed with insecticidal soaps , neem oil , or the beneficial bacteria , Bacillus thuringiensis ( BT ). Beneficial insects can also be released that can feed on or infect corn earworms by introducing a virus that is fatal to the insect , but harmless to plants and humans .
European Corn Borer ( ECB )
European corn borers ( Ostrinia nubilalis ) first made “ landfall ” in North America in the early 20th century . With the move to bioengineered corn over the past few decades , their original host species is becoming resistant to their damage and they have moved on to find cannabis a suitable host . When ECB feeds on the stalk of cannabis , cankers form , which weaken the stems . This causes branches to bend and break leading to wilting leaves or even broken buds . To further add insult to injury , their points of entry often leave opportunistic fungi a place to set up , as well as other insects to enter . Damage occurs from full-grown larvae . Each is 2-2.5cm long with dark spots on a cream or gray-coloured body . They overwinter inside infected stems . They pupate in May and emerge as brown moths . Females lay their eggs in the evening and they can hatch as soon as three days later . A second generation peaks in mid-late summer , ceasing their feeding once late September rolls around .
“ This roster does not
reflect all possible cannabis pests , though these are the more common ones and the ones known to do the most economical damage to cannabis .”
Control is difficult since ECB feeds from the inside of the stalk . There are short windows of opportunity to kill the larvae right after eggs hatch before they burrow into living tissue . Eggs are laid on lower leaf surfaces . When the black heads of the larvae are visible within the egg , hatching will occur within the next 24 hours . This is the time to try to eradicate them . At the end of the growing season , if possible , stalks should be chopped up and field debris tilled under or removed to try to kill overwintering larvae within the stalks .
Hemp Borer
The Eurasian Hemp Borer ( Grapholita delineana ), also known as the hemp leafroller and hemp seed eater — but also simply known as the hemp borer — not only does as its name suggests , bore into cannabis stalks , but it also eats the leaves , flowers , and seeds . Adults are moths with a 13mm wingspan , whose forewings look like a boomerang when they are drawn back . They lay their eggs on cannabis leaves . The orange larvae that emerge five to six days later , are about 6.5mm long with dark brown heads . There are two or three generations per year depending on weather . The hemp borer is not as well studied as the ECB , but it is presumed to overwinter much like it . Adults are not thought to be strong flyers , so outbreaks tend to happen in concentrated areas and the same areas in successive years if not treated . Well-timed sprays at egg hatch , and before the larvae have bored into the stems are the best way to control them . Crop debris should be collected and destroyed at the end of the season and cannabis crops should be planted at a distance from the previous year ’ s crop as an additional precaution .
Japanese Beetle
The Japanese beetle ( Popillae japonica ) is another insect that poses a threat to cannabis as both larvae and adults . The larvae are easily identifiable as white grubs found in the soil or grassy areas . They are C-shaped and about 2cm in length . They feed on the roots of cannabis and just about anything else until they emerge as adults in early to mid-summer . Adults are metallic green with bronze wings and white spots on their abdomen . They lay eggs in late summer which will then overwinter and pupate into grubs , starting the cycle over again .
44 Maximum Yield