APIS - Biocontrol Information

Introduction

This section is designed to acquaint the user with general procedures used to collect the organisms (mainly insects) that feed on and hence damage the four nuisance aquatic plants included in this system. In this section only an overview will be given, with more plant and insect specific information given in the sections concerning insect and damage descriptions.

Basically four types of procedures are used to collect insects and related organisms that feed on and damage the nuisance plants contained within this system. These procedures include 1) hand collection, 2) sweep netting, 3) extraction techniques, and 4) infested plant removal.

Knowing the correct and most time efficient collection procedures will allow personnel at the operational level to accurately and rapidly determine population levels of the agents. Information on population level is important in determining potential impact on the plant infestation by the agents as well as for supplementing the agents in areas where their population numbers are low or nonexistent. Determining numbers of agents in a systematic manner is an important first step in utilizing insect Biocontrol technology more actively in existing aquatic plant management programs (see also: Using Biocontrol Agents More Actively).

Hand Collection:

As the name implies, hand collection techniques are nothing more than simply collecting the agents by hand directly off the plant. For many insect species this is the best and most efficient manner to collect large numbers of organisms. While this technique sounds easy it is best to understand a little about the life history of the organism before attempting to collect large numbers.

For example, hand collection techniques are an efficient way to collect large numbers of both species of adult waterhyacinth weevils (see also: Neochetina eichhorniae - "Mottled Waterhyacinth Weevil" and Neochetina bruchi - "Chevroned Waterhyacinth Weevil"). However, the ability to collect large numbers is dependent on knowing where on the plant to look for the adults. Both of these species tend to reside in the unfurled wrapper leaves and within the leaf sheaths or ligules. They are not found within the plant or simply crawling along the exposed leaf surfaces.

In most cases the organisms can be simply removed from the plant by hand. However, in certain cases additional equipment will be necessary because of the small size and delicate nature of the organisms. Such equipment may include forceps or small battery-powered vacuum cleaners for picking up the insects.

Netting:

The use of an insect net is a common collecting technique used by entomologists to gather certain species of insects. In the case of the organisms contained within this system, sweep netting is probably one of the least efficient. One species that can be collected using this technique is adults of the alligatorweed flea beetle (see also: Agasicles hygrophila - "Alligatorweed flea beetle" ). Large numbers of adults can be collected relatively rapidly using this technique.

The use of a sweep net is not difficult but usually requires practice to become efficient. To correctly use a sweep net, hold the net with both hands with the net handle directed forward and the net opening pointed sideways. Swish the net from side to side in a small arc in front of your body as you walk slowly forward. As the net reaches on the side of your body, begin to return the net to your opposite side. Be careful when switching directions since insects can escape at this time. Therefore, quickly flick the net over to close the bag against the net frame when changing directions.

Similarly, when ready to remove the insects, close the opening to the net by allowing the end of the bag to drape over the circular net frame. Since the insects will be alive (of course), carefully remove the entire contents to a plastic bag for later sorting. The presence of bees and wasps is a distinct possibility, so remove the organisms with great care.

Extraction Techniques:

Since a majority of the organisms feed within the plant tissues, a more efficient and less time-consuming procedure must be used to collect high enough numbers. In this case a passive technique using specialized equipment to extract the organisms directly from infested plant material is used. The most commonly used equipment is the Berlese funnel.

As the name implies, the Berlese funnel is a large metal container shaped like a funnel that uses heat and light to desiccate or dry infested plant material contained within the funnel. The process of plant drying forces the insects to seek wetter plant material until they eventually fall into a collecting container located at the bottom of the funnel.

Berlese funnels can be purchased from a variety of sources, but with ingenuity one can be built with little effort. Imagine a funnel held upright by a large stand. Within the funnel is a piece of hardware cloth or screen upon which rests the infested plant material. A 60- to 75-watt fixture is placed on top of the funnel. The light fixture covers but does not completely seal the funnel off. It is important for air to circulate within the apparatus for slow and even drying of the plant material. At the bottom of the funnel is a small glass jar (Mason jars work great) filled with a small quantity of the appropriate plant material. As the plant material within the funnel dries from the top down, the insects are forced to seek moister material until they eventually fall into the collecting container.

Large amounts of plant material can be processed very quickly using this method.

Removal of Infested Plant Material:

In many cases, especially when insect populations are high, there is no need to extract the organisms from the plant material. Instead, the plant material can be moved directly to the site where the agent levels are low. This is a highly efficient technique that requires little effort, but only works when population levels are high. If levels are low, large amounts of biomass must be moved to allow for significant increases in population levels at the new site.

Anatomical Directions

This section defines terms that relate to positions on the body. These include such terms as anterior, posterior, lateral, etc. These terms act as highway signs to the various parts of an organism. It is much easier to relate to the front of the body by referring to the anterior portion instead of such vague terms as top, front, etc.

If you plan on continuing to identify various species, it would be helpful to learn the correct terms associated with position on the body.

Anterior: The top or front end of an organism's body, or at or towards the front.

Posterior: The behind or end of an organism, or at or towards the rear.

Dorsal: The back of an organism, or on or towards the back.

Ventral: The bottom of an organism, or on or at the bottom.

Lateral: The sides of an organism.

Basal: The bottom of an elongated structure or towards the base.

Distal: Towards or at the tip farthest away from the base.

Bilateral Symmetry: An organism is bilaterally symmetric if when cut from anterior to posterior the resulting halves are equal. Humans exhibit bilateral symmetry.

Radial Symmetry: An organism is radially symmetric if when cut in half the resulting pieces are not equal. A starfish whose body plan is built upon a circle exhibits radial symmetry.