Article 3-1 Insecticide

Erik Biksa (dip-ag)

Pests, which include insects, can be defined as: any organism causing injury, danger, or annoyance to man, property, or animals. In controlled growing conditions insects reduce yield and marketability, increase cropping expenses, are vectors for disease, and at worst, can result in entire crop loss.

The best way to deal with the problem is to avoid it. Insects may enter the grow room on you, your pets, through cracks, new plants, or even hitch a ride on the fresh air intake. If you have been out of doors or tending other house plants, make sure to wash your hands and exposed areas, while changing clothes or protective outerwear.

Ducting into the grow area should contain a fine screen or HEPA filter. Keep in mind, that this may restrict airflow significantly. Increased fan requirements and/or inline booster fans may be required. Make sure to clean the intake screen or replace filters often, as dust and other build up will further restrict airflow. Spray your filters with a Pyrethroid with a long term residual-Permethrins work well and have very low toxicity.

Before introducing a new crop into the grow room, fumigate or scrub the area thoroughly. Total Release Fumigators do a reasonably good job of debugging the area. Be careful when using these types of products. Some are lethal to plants, humans, pets, and can ignite fires. Follow the directions to the letter. The safest and least toxic are pyrethrum based.

Quarantine new introductions before setting them out into a healthy grow room. Watch for signs of insects and disease. If cloning, keep in mind that the longer a plant is in production, the greater the chances are of developing a problem.

Make sure that the grow area is well sealed. Large sheets of polythene make an excellent barrier to prevent entry. Take care to seal around doorways. Non-insecticide botanical extracts such as a garlic spray help to make a plant less visually appealing to a passing extract. It is also true that garlic does have some insecticide like properties if sprayed directly onto pests.

It is likely, no matter how careful the grower is, that at one time or another a harmful insect will appear. Now, the big question is, what are some effective ways to deal with the problem? It is not the intention of this article to go into any great depth on particular insects there are many resources on the subject. But, there are some suggestions as to ways to effectively, and safely deal with them.

Obviously, you need to identify the type(s) of insects you have discovered while making your routine checks. Some may be harmless or even beneficial; others are your worst nightmare. Know your enemies-get to know the life cycle. For example, the two-spotted spider mite can produce a new generation in as little as three days, under warm dry conditions. In cooler, damper conditions it may take as long as 20 days. In this example, the growing conditions might dictate the frequency of treatments.

Most insects which attack indoor and greenhouse crops have piercing and sucking mouthparts, while outdoor pests more commonly have chewing mouthparts. These pests include spider mites, aphids, thrips, and whitefly. Some species of spider mites are specific to certain types of crops.

Knowing how the insect feeds (sucking vs. chewing) will help you to determine the type of insecticide you need because of the mode of entry.

There are five general modes of entry for insecticide:

  1. Stomach Poisons – chewing insects are more susceptible than sucking insects.
  2. Systemic – act in plant tissue, insect eats then dies.
  3. Contact Sprays – only kills on contact, good for rapidly moving insects.
  4. Residual – organic and inorganic, absorbed by the insects nervous system.
  5. Fumigants – gets into insect’s respiratory system.

There are six general classes of insecticides that affect the plants nervous system. The type you choose should be dictated by the type of crop you’re growing and time until harvest.

  1. Organophosphates – low persistence (breaks down readily), high dermal toxicity (easily absorbed by skin), low to very high toxicity. Dursban has been banned for home use by the EPA- effective June 2000.
  2. Carbamates – low to medium persistence, low to high toxicity, low dermal toxicity.
  3. Chlorinated Hydrocarbons – high persistence, easily absorbed by fat cells, low to medium toxicity.
  4. Botanicals – often the best choice for crops intended for human consumption, high toxicity (usually to insects), low persistence. This includes natural pyrethrum (Chrysanthemum extracts), nicotine sulphate
  5. Synthetic Pyrethroids – similar to botanicals, low to medium toxicity, low persistence.
  6. Bacterial Fermentation By Products – effective against internal parasites ( such as leaf miners), systemic, medium persistence, low toxicity.

Other chemical controls which do not affect the insects central nervous system:

  1. Bacterial agents, such as BT.
  2. Insect growth regulators.
  3. Anti-metabolites.
  4. Pheromones.
  5. Feeding Deterrents, such as neem oil, garlic, and hot pepper extracts
  6. Repellents, such as plant extracted terpines (essential sprays).

Always follow the manufacturers directions for frequency of application. Take the time to schedule applications to follow the crops life cycle, as there are a recommended limit of days to harvest after applications. Many will break down faster in high light conditions and in the root zone at lowered pH levels. External products will breakdown, but systemic’s may take longer to flush out than expected.

Pests can develop resistance to the same class of insecticide and/or the A.I. (active ingredient). Keep in mind new generations may arise within five days, so there seems to be an accelerated rate of evolution going on in their world. So different A.I. or modes of entry should be applied in rotation.

Dip entire young seedlings or clones in a mild contact solution such as insecticidal soaps containing fatty acids, or hot pepper or neem extracts. Always try sprays, etc. on a few trial plants first, as some plant varieties are more sensitive than others. If problems have been persistent in the past you may consider a systemic treatment, if accounting for days required before harvest and environmental conditions. Keep in mind that many label recommendations are intended for outdoor or greenhouse crops, which often receive higher light levels, rain, etc. than what is more common to indoor grow rooms.

You can spray a deterrent on or around plants frequently, even if the problem does not persist. Spraying a contact spray such as pyrethrum around the plants is also good for preventing infestations, and if insects do persist spray directly onto the plants almost up to harvest. No matter how safe the product is, always be sure to rinse your plants near harvest. Take care not to develop mold from drenched leaves and flowers, and watch for sunscald from wet foliage in high light conditions. When using contact sprays, be sure to maintain a safe distance from the plant in order to prevent burning of the foliage. Surfactants and wetting agents increase the efficiency of application and rinsing of insecticides, only small amounts are required.

Insecticides are not the only solution, whether organic or inorganic. Prevention is the best step. Beneficial insects, which are specific predators to your problem are also often a viable chemical free solution. Insects have plagued man since the beginning, so there is a great deal of information and products to choose from. Take the time to get to know the problem and how best to effectively deal with it.