Caterpillars on Cannabis Plants

During the outdoor growing season there are many insects that feed on our marijuana plants. Caterpillars are the larvae of insects of the Lepidoptera family, more known after their metamorphosis into beautiful butterflies. There are many species of butterflies that can be found all over the world so there will also be many types of different caterpillars, with different colours and sizes but with clear characteristics in common, such as a segmented body, their 6 legs or the hooks of their false legs. 

Caterpillars have a long body divided in segments of different colours, generally adapted to camouflage themselves among the vegetation, avoiding this way to be eaten by birds or other natural predators of these insects. They move using their 6 main legs along with 10 false legs distributed throughout their body, which can be located in different parts according to the type of Caterpillar.

How to detect the attack of caterpillars?

List of symptoms

– Holes with brown trails around them
– Chew marks on the leaves
– Yellowing on the top leaves
– Holes and damage to the stems

Avoid butterflies and moths! Although these beautiful creatures look great resting on your cannabis plants, they lay eggs that hatch into caterpillars! Don’t let them hang around your garden! Butterflies generally deposit their eggs prior to the arrival of the winter season, so these eggs will hatch when ambient temperatures are the appropriate, needing the heat of the end of summer, which coincides with the arrival of winter in about two months. It is very feasible that butterflies deposit their eggs and these don’t hatch until appropriate conditions prevail.We must thoroughly observe the plant, looking at those leaves or buds that are found in the highest parts of the plants, where butterflies lay their eggs. At first sight it’s really complicated to be able to see the eggs, but if we carefully examine the plant they will be distinguished as small sets of dots that acquire different colours (white/yellow) and shapes (round or oval), depending on the type of butterfly egg.

After this initial inspection – and during the whole flowering period – we must look at the buds, starting at the top and thoroughly examining the rest of the plant in search of small black remains or darker parts of the buds, which are sign of rottenness. The first attacked flowers are the bigger ones, but without being extremely compact,  so caterpillars can easily pierce them and devour the softer tissues, such as the small branches of the lower parts of the buds.

In the case of finding a caterpillar, we should make a daily  inspection of the whole plant, especially on those hours when the Sun is low and the ambient humidity is high, although it is very easy to  find them on the rest of the day, eating nonstop, as their hunger is insatiable and voracious.

If a caterpillar is detected or if we observe any bitten bud -we should apply a product that repels or kills the eggs and larvae of butterflies. These products are generally created on the basis of a gram-positive bacillus that is naturally found in the soil and also on plants. Such products are specifically created to treat lepidoptera larvae plagues, being more or less effective depending on the type of larvae to treat, but always offering great results.

In the case that the plague appears just before the harvest we have to carefully observe the plants every day, opening the buds to see if caterpillars are hidden inside the flowers.

If we don’t proceed this way it’s very possible to harvest the plants with the larger buds clearly affected or even to throw them away because of caterpillars bites and defecations, which cause the appearance of fungi like botrytis.

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In the case of having the plants affected by botrytis, you can treat them as long as you can leave a security period of 15 days before harvesting the plants. If  the end of the flowering stage is near, the best will be to look at the state of the trichomes and – if these are mature enough  – harvest the plants.

Once harvested, we should instantly proceed to remove the infected parts from the healthy ones. If we do not separate these parts infected with fungus this will extend to end up rotting the whole bud, even during the drying phase, as it requires a few days to lose much of the humidity contained in its metabolism.

After harvesting the marijuana plants we should hang the plants upside down to perform a proper drying of the cannabis buds. In this way, plants lose their humidity and stop being a good hideout for those caterpillars that have been able to survive the purge realized by hand.

These caterpillars will leave the plant to be able to become butterflies, so when plants are dried, we’ll be able to see the caterpillars sliding down from the bud making rappel until arriving to the ground.

Once arrived to the ground, they will quickly seek another vital sustenance to be able to feed and continue their vital process, so it’s important to recover these caterpillars to prevent that they fill our house with cocoons and later with butterflies, as they embed in the most unlikely and generally inaccessible places.

Recommendations for a crop without caterpillars:

  • Locate the butterflies that lay down on the plants.
  • Look for eggs on the leafs.
  • During the flowering phase, control the buds looking for signs of bites.
  • In case of detection, apply Biothur or another product against caterpillars.
  • Stop applying the product within the last 15 days.
  • Review the plants and buds after harvest and remove the infected or bitten parts.
  • Capture the caterpillars by hand in the case of not being able to apply the product.
  • Leave comments or questions below!

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