APHIDS: What You Want to Know About Them and How to Organically Get Rid of an Aphid Infestation in Your Cannabis
Aphids are a common pest
What does an Aphid pest look like?
Aphids are small, pear-shaped soft-bodied insects about 1 to 3 mm long. Like all insects, they have six legs, a pair of antenna, and three body segments: head, thorax and abdomen. There are thousands of species that vary in color from green to yellow, black or brown. Some have wings, some are covered with wax or “wool” made from webbing they secrete and others have unique distinguishing features.
Common to all aphids, distinguishing them from all other insects, are a pair of “cornicles” which extend like tailpipes from their abdomen. These can vary in length and color.
Where is the pest found?
Aphids colonize the stems and undersides of plant leaves. Some species, such as the black bean aphid, are quite noticeable because their color stands out from the plant. Others, such as the green peach aphid, are often colored spring green and blend in with young leaves.
What do Aphids do to the plant?
Aphids are true bugs. Like all bugs, they live on plant juices by puncturing leaves using a straw-like mouth called a proboscis to suck sap from stems, branches and leaves. In order to obtain enough protein, aphids suck a lot of juice, extract the protein and excrete the concentrated sugar solution that is referred to as “honey-dew.” The aphid excrement attracts ants that herd the suckers, protecting them from predators. Honeydew is a growth medium for sooty fungus, which causes necrosis of leaf parts.
Heavy aphid infestations cause leaf curl, wilting, stunting of shoot growth and delay in production of flowers and fruit, as well as a general decline in plant vigor. Aphids are vectors for hundreds of diseases and can quickly cause an epidemic. They transfer viruses, bacteria and fungi from plant to plant.
What you want to know about Aphids
Aphids are true “bugs,” sucking insects in the order Hemiptera. Most aphid species have a complex life cycle. Many species overwinter as eggs, but during most of the season they are nonsexual and deliver nymphs pathogenically. These nymphs are live-birthed and born pregnant. A single species produces populations that differ depending on the season. For instance, seasonally, when infestations become dense, some populations have wings and colonize new plants by traveling on air currents. Each live-birth generation exists for only 7 to 14 days. If left unchecked, aphid populations rapidly grow to thousands.
Sexual populations appear in the fall, resulting in eggs that overwinter. All species have temperature-dependent rates of reproduction. But even at the same temperature, aphids may reproduce at different rates based on nutrition from the host plant.
Most aphids live only in the plant canopy. Root aphids, most commonly the rice root aphid, live in the planting medium and feed on the roots, making early detection and treatment much more difficult.
Indoors, with no predators to keep them in check, aphids can overrun a cannabis garden in short order.
How to prevent Aphids
Aphids are airborne for part of their life cycle. Use a 340 micron mesh or filter to keep them out of the grow space. A thrips screen should be used in the garden. It works on aphids as well.
Check the plants regularly for aphids—at least twice weekly when plants are growing rapidly. Most species of aphids cause the greatest dam-age when temperatures are warm but not hot (65-80°F). Inspect root zones and around the tops of pots for aphids in the media. Shaking a container can dislodge some aphids from bottom of the container. Use this technique to spot occurrence.
Catch infestations early. Once their numbers are high and they have begun to distort and curl leaves, aphids are hard to control because the curled leaves shelter them from insecticides and natural enemies.
Aphids tend to be most prevalent along the upwind edge of the garden and close to other sources of aphids, so make a special effort to check these areas. Many aphid species prefer the undersides of leaves, or tender terminating stalks, so check there.
Aphids usually feed on the underside of leaves or on stems. Colors include black, green and red. Once aphid infestation is identified, investigate its extent, then treat aggressively. Dead aphids leave white remains of their exoskeletons. These are sometimes mistaken for other organisms.
Outdoors, check for evidence of natural enemies such as lady beetles, lace-wings, syrphid fly larvae and the mummified skins of parasitized aphids. Look for disease-killed aphids as well: they may appear off-color, bloated, flattened or moldy. These observations should be considered when evaluating treatment strategies. Substantial numbers of these natural control factors can mean that the aphid population may be reduced rapidly without the need for treatment.
Some species of ants farm aphids, carrying them to fresh grazing areas and protecting them from predators. They collect the honeydew, the concentrated sap excreted by the aphids. If you notice ants in the picture, you will have to control the aphids.
How to control Aphids in your outdoor cannabis garden
Sometimes aphids must be controlled outdoors. Often this can be accomplished by spraying them off with water. Spraying several days apart will knock down the population considerably, reducing plant stress. If aphids remain a problem, consider one of the controls listed in the indoor section below.
Check for ants: when they are present aphids are much more difficult to control, so they must also be eliminated.
How to control Aphids in your indoor cannabis garden
Indoors and in the greenhouse aphids have an easy life. Without threats from weather and by living in a relatively predator-free area, they don’t suffer losses to these relentless killers. Without the pitfalls they suffer in nature, aphid population growth reaches exponential proportions quickly.
Since the balance of nature isn’t operative indoors, the gardener must intervene before an outbreak has reached epic proportions. There are a lot of choices:
Professionals often use parasitoids when there is an out-break that hasn’t reached epic proportions. Predators are recommended for heavy infestations. However, this may reflect professionals’ preference for aggressive predators over subtle parasites. The predators spend a portion of their life eating aphids, and close-up their actions can be as vicious and dramatic as an alligator’s.
The parasitoids inject an egg into the aphid. The egg hatches and the parasitoid larvae feast inside. Most aphids die within one to two hours of this egg-laying. The body of the aphid undergoes a dramatic change as it becomes a “mummy” changes color and bloats. Each larva emerges as an adult Alien-style from the mummy. Not quite as dramatic, except when the adult crawls out of the corpse, but every bit as effective. The old mummy remains stay on the leaf.
Among the most important natural enemies are various species of parasitoid wasps (such as Aphidius colemani, Aphidius matricariae and Aphidius ervi) that lay their eggs inside aphids. The generation time of most parasitoid wasps is quite short when the weather is warm, so once mummies begin to appear on the plants, the aphid population is likely to be reduced substantially within a week or two. These wasps are tiny and do not have stingers so they pose no threat to people or pets.
Many predators also feed on aphids. The most well-known are the common lady beetle (Hippodamia convergens), green lacewing (Chrysopa rufilabris) and predatory flies (Aphidoletes aphidimyza, Aphidius colemani, Aphelinus abdomi-nalis, Aphidius ervi). Naturally occurring predators work best, especially in small backyards. Commercially available lady beetles may give some temporary control when properly handled, although most of them disperse away from the yard within a few days. They are most effective in protecting large areas rather than small plots, which they are likely to leave in search of dense prey infestations.
Aphids are very susceptible to fungal diseases when it is humid. Whole colonies of aphids can be killed by these pathogens when conditions are right. Look for dead aphids that have turned reddish or brown; they have a fuzzy, shriveled texture unlike the shiny, bloated, tan-colored mummies that form when aphids are parasitized.
How to make an organic pesticide recipe using the dead aphids
Make a pesticide by taking these dead aphids, blending them with water (1-3 teaspoons of aphids per quart) and spraying the solution on plants.
There are also biological controls of aphid infestations
• Beauveria bassiana (beneficial fungi) • Capsaicin • Carbon dioxide • Cinnamon oil • Cloves • Coriander oil • Garlic • Horticultural oil • Insecticidal soap • Neem oil • Peppermint oil • Pyrethrum • Soap • Vacuuming
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