Good farmers treat pests, great farmers prevent pests.
Adapted from Industrial Hemp USA by Paige Della-Franca
The idea of integrated pest management IPM employs cultural, biological and chemical applications from a holistic perspective. IPM’s claim to fame is substituting the notion of eradication with coexistence in order to maintain a more ecologically friendly balance that does not effect the economic potential of the crop. Below I have displayed a few of the most common pests you will encounter and solutions from a panel of farmers. As a rule of thumb its best to rotate these products to decrease the likelihood of the pests developing tolerance. Methods that growers should adopt if cloning include organic chemical treatment of mothers before cloning, on clones after being transplanted a couple of days and treatment right before flowering occurs. (McPartland 2000) It is suggested to stop spraying within seven days of flowering if possible to prevent any effects on aroma and residual content.
MITES, APHIDS AND THRIPS
When we talk about mites, in this article we are addressing specifically spider and russet mites. They can be devastating if not dealt with preventably or immediately when noticed. If you are working in a greenhouse and notice this infestation it is common for people to completely empty and clean the greenhouse or to quarantine infected plants. From experience quarantining is effective, but to really solve the problem, cleaning everything is the best. For viewing before buying or viewing in general check out this 60x magnification lens from amazon.
Some of the most common and devastating pests, typically found in greenhouses from clones of infected mothers. Preventative measures are advised as early symptoms are not obvious. The bottom most leaves are infected first. You may see small puncture wounds called stipples that form parallel lines to the leaf vein. Another way to spot early on is by turning the leaf over and inspecting with a microscope. Later on damage could be devastating such as leaves turning yellow, drying up and dying. Towards flowering infestation is obvious and seen by webs forming over flower material.
Biocontrols: a mixture of Phytoseilus persimilis, Neoseilus californicus, and Mesoseilus longipes (McPartland 2000)
Predatory insects are available.
Fungi: Neozygites floridana and Hirsutella thompsonii (Conidia)
Russet mites thrive in greenhouse environments. They are also nearly impossible to see without magnification. The first symptoms include leaf curling on the edges and then as the mite population multiplies the plant starts to discolor. The discoloration is almost a beige/tan color, the same color of their tiny bodies. (McPartland 2000) Biocontrols and predatory insects are very limited on the commercial market to specifically control russet mites. Fungi is seemingly effective used alongside other organic chemical products listed below. (Linquist et. al. 1996)
Fungi: Hirsutella thompsonii (Conidia)
AKA plant lice! yuk! Aphids can develop wings but not all do. The worst about aphids is the fact they have a symbiotic relationship with some viruses. (Kennedy et. al. 1959) Six different species of aphids are attracted to hemp and thrive in windless environments, humid environments. In the south there is not much you can do about the humidity if working outdoors but installing fans in greenhouse spaces or planting in areas with a slight breeze is a great mitigation method. Identifying aphids early on is extremely difficult so prevention is key. Early signs have been noted by yellowing spots under leaf and puckered leaves. (Kirchner 1906)
Mechanical control: hanging sticky traps
Beneficial insects: green lacewings, lady beetles and others. Please research before use.
Organic chemical home remedy: add 4 hot peppers, 1 onion, 4 cloves of garlic to 2 quarts and let set several days then strain. Next add 1 tsp of dish soap and spray undersides of leaves. Insecticidal soap, diatomaceous earth and clay microparticles can also be employed. (Bush Doctor 1985)
Bush Doctor, The. 1985.Aphids or plant lice. Sinseniilla Tips 5(2):22-23.
Kennedy JS,Booth CO, Kershaw WJS.1959.Host finding by aphids in the field. At~nalsApplied Biology 47:424-444.
Kirchner 0 . 1906. "Hanf, Callnabis sativa L." pp. 319-323 in Die Kraitklreiten ~ t n dBefehadigungen ulzfrrerandwirtschaftliclzen Kl~lturpjlanzenE. . Ulmer, Stuttgart. 637 pp.
Lindquist EE, Sabelis MW, Bruin J, eds. 1996. Eriophyotd Mites: Their Biology, Natural Enenlies and Control. Elsevier Science, Amsterdam. 790 pp.
McPartland J.M., Clarke R.C. & Watson D.P. 2000. Hemp Diseases and Pests Management and Biological Control. Cabi Publishing
Other online resources: