Cannabis is a very tolerant species when it comes to insect pests . In fact , cannabis leaves are sometimes used as a repellent for pests in some parts of the world . This does not mean that cannabis , the plant , is never preyed upon . Of the roughly 300 or so different insects or arachnids that can be found on or around field-grown cannabis , only a dozen or so are of concern enough to cause economic damage . With limited exceptions , some of the same pests that bother other field crops bother cannabis . Before attempting to remediate any pest problem though , make sure the product selected ( i . e . insecticides or miticides ) is approved for use on cannabis crops . Unfortunately , this segment of the industry is lagging behind , as the cultivation of cannabis becomes legal in more and more places , but more and more insecticides are being approved to use . To learn what some of the more common pests are of outdoor-grown cannabis , read on .
Common Insect and Arachnid Pests of Field-Grown Cannabis
Aphids
Aphids are hard to avoid no matter what you are growing . There are species with specific hosts , such as the cannabis aphid ( Phorodon cannabis ) and hops aphid ( P . humuli ). Other species are generalists , like the green peach aphid ( Myzus persicae ) and black bean aphid ( Aphis fabae ). With some variation between species , adult aphids are about 4.5mm long , and range in colour from cream to pink to green . There are both winged and non-winged forms . Aphids damage leaves and flowers causing wilting , yellowing , and distorted appearances . They cause further issues with their excrement . It attracts ants and , in many cases , causes black sooty mould on leaf surfaces where it lands . There are multiple generations each year and the females are born pregnant , causing populations to explode exponentially very quickly . Fortunately , there are a lot of natural predators that feed on aphids . Insecticide sprays should only be used on populations that are swelling . Declining aphid populations imply that nature is taking care of the problem for you .
Corn Earworm
Not to be confused with the European Corn Borer , the Corn Earworm ( Helicoverpa zea ), damages cannabis crops by feeding on the flowers , seeds , and leaves of the plant , but they do not bore into it . These pests are alternately known as the cotton bollworm or the tomato fruitworm and do their damage in their larval stage . Larvae can be up to 4cm long . They range in colour from green and tan , to brown or reddish and black . Their head is tan and the underside is a lighter colour . They have alternating light and dark stripes running down their bodies , coupled with some additional dark spots . The adult moths are lighter in colour ; usually a tan of buff hue , with a dark band on both their fore- and hindwings . Their wingspan is about 3cm . Corn earworm does not overwinter in colder climates , but instead migrates anytime between early to late summer . Their eggs hatch within three to four days of being laid , and they complete their life cycle within three weeks , so even if they don ’ t show up until late August on your crops , there is still time for them to do some damage . Fortunately , the damage they do is mostly superficial and does not reduce yield except for in extreme infestations .
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