Handbook of Vermicomposting by E.SREENIVASAN - HTML preview

CHAPTER 8

TROUBLE SHOOTING

Let us discuss some of the common problems you may experience while working with your vermicomposting systems and the solutions to deal with these issues here:

1. Temperature

Heat as well as cold cause many problems for vermicomposting. A red wiggler becomes inactive once the temperature of the bedding rises above 29oC. This could be avoided by placing the bin under shade at all times, if placed outdoors during the warm seasons. Evaporative cooling of the moist bedding keeps the bin cooler than the air temperature, but may need to add more water during the summer. The greater danger of overheating the worms arises from heat produced within the bin, which could be reduced substantially by feeding small amount of food frequently rather than a bulky food at one time. In general, worms like cool weather. They are at their highest activity and reproductive levels as the weather cools in the fall and warms in the spring.

2. Aeration

It is important to construct the bin to allow adequate airflow. Holes may be drilled on the upper sidewall of the bins for air circulation. Holes drilled on the lid may allow water inside during the rainy season. The type of bedding used also influences air circulation. Coarser bedding such as chopped leaves allows more air to circulate than fine textured bedding such as peat moss or shredded paper. As the composting process progresses, the bedding becomes more finely textured. This can be alleviated to some extent by periodically adding fresh bedding. Other ways to promote aeration includes occasional fluffing of the bedding material, avoidance of deep bedding (a maximum of 30cm), over-feeding and over-watering.

3. Acidity (pH)

The decomposition of organic matter produces organic acids that lower the pH of the bedding soil. The best way to deal with this is to add several cups of ground limestone to the bedding and in the application of Zeolite in proper amount. Limestone will serve dual purpose - maintaining the acidity and acting as a source of calcium to the worms. Other products, which can 40 be used, are powdered limestone, dolomite limestone. Baking soda should be avoided because of its high sodium content.

4. Pests and Diseases

Vermicompost worms are not subject to diseases caused by microorganisms, but they are subject to predation by certain animals and insects (red mites are the worst) and to a disease known as “sour crop” caused by environmental conditions. A brief overview of the most common pests (see Fig.11) and diseases is given below: 

• Ants. These tiny insects are a real problem because they not only consume the feed meant for the worms but are also found to attack young worms causing serious injuries. Ants are particularly attracted to sugar, so avoiding sweet feeds in the worm beds reduces this problem to a minor one. Or constructing a water-channel around the vermi-tank (at the bottom) will permanently solve the ant-problem.

• Rodents. Worms are a favorite natural food for many small animals like rats. So if a rat gets access to your worm bed, you can lose a lot of worms very quickly. Rats and mice can chew through plastic or wood easily, and don't need very much space to move through a surface. This is usually only a problem when using open-air systems in fields. It can be prevented by putting some form of barrier, by using wire mesh for the lids.

• Birds. They are not usually a major problem, but if they discover your vermibeds, they will come around regularly for the worms. Putting a lid over the tank or cover over the material in the open-air systems, will eliminate this problem. These covers are also useful for retaining moisture and preventing too much leaching during rainfall events. Old carpet can be used for this purpose and is very effective.

• Centipedes. These insects eat compost worms and their cocoons. Fortunately, they do not seem to multiply to a great extent within worm beds or windrows, so damage is usually light. If they do become a problem, one method suggested for reducing their numbers is to heavily wet (but not quite flood) the worm beds. The water forces centipedes and other insect pests (but not the worms) to the surface, where they can be destroyed by means of a hand-held propane torch or something similar.

                          Fig.11: Common pests of vermibeds

• Sour crop. This is reported to be the result of poisoning caused by having too much protein in the bedding. This happens only when the worms are overfed. Protein builds up in the bedding and produces acids and gases as it decays. Farmers wishing to prevent sour crop should work by not overfeeding and by monitoring and adjusting pH on a regular basis. Keeping the pH at neutral or above will preclude the need for these measures.

• Mite Pests. Insects are attracted to wormbeds due to its moist and organic environment. If the bedding is not properly maintained, acidity build up in the bedding soil may invite the mites as they are attracted towards an acidic, moist environment. Although small populations of mites thrive in all worm beds, they might create problems when present in excessive numbers. The mite populations at high level scan also cause worms to bury deep in their burrows without feeding.

White or Brown Mites

White or brown mites are not predaceous and tend to feed only on decaying or injured worms. However, during infestations, these mites can devour much of the food in earthworm beds, depriving earthworms from the nutrients.

Red Mites

These mites first appear as small white or gray clusters, resembling mould, which under magnification would reveal the clusters of juvenile red mites in various stages of development. The adult red mite is smaller than white or brown mites with bright red colour and an egg-shaped body with four pair of legs. The red mites are known to be parasitic on earthworms. It attaches to the worm and relishes its coelomic fluid. They are also capable consuming the cytoplasmic fluids from egg capsules.

Mite Prevalence and Prevention

Harmful buildup of mites can be prevented by taking proper care of worm beds. The conditions usually associated with high mite population are:

a. Excess water: Beds that are too wet create conditions that are more favorable to mites than to the worms. Excessive wetting of beds may be avoided by adjusting watering schedules, improving drainage, and turning bedding frequently.

b. Over feeding: Excess food can lead to an accumulation of fermented feed in worm beds and lower the pH of the beds. The feeding schedules may be adjusted and modified according to seasonal variations. The pH of beds should be maintained to neutral (pH: 7), using calcium carbonate as the buffering agent

c. High moisture content feed or fleshy feed: vegetables with high moisture content can attract high mite populations in worm beds. Use of such feed should be limited, and if still, high mite populations persist, this feed should be discontinued until mite populations are under control.

Mite Removal

Several methods have been suggested for removing mites from earthworm beds. However, any type of mite removal, physical or chemical, will only be temporary unless worm-bed management is altered to make conditions less favorable for mites. The following techniques range from low- to high-intensity measures.

* The worm beds should be exposed to sunlight for several hours, however one should make sure that the earthworms are not directly exposed to sunlight. The amount of water and feed should be reduced. This will further encourage the mites to leave the beds.

* Moistened newspapers or burlap (jute) bags may be placed on top of the

beds, and these can be removed as mites accumulate on them. This procedure may be repeated until mite populations are substantially reduced.

* Pieces of watermelon or potato slices may be placed on top of the worm beds. The peels could then be removed with the mites.

* The bed may be watered heavily without flooding. This will compel the mites to move up to the surface. The mites can then be scorched using a hand-held propane torch. This procedure may be repeated several times, at three-day intervals, if needed.

* Light sulphur dusting will kill the mites. Or bed may be wetted (as suggested above) and then the sulphur added directly to the mites. Sulphur should be applied at the rate of approximately 2 g per 0.93 square meter of bed. Sulphur will not harm the worms, but in time, it may increase the acidity of the bed. In the past, some chemical pesticides have been used in worm beds. However, due to their biomagnification, it is not advisable to use these chemical compounds. Although safer miticides do exist in the market they are not specifically made for the Vermibed.

5. Odour Problems

The problem of unpleasant odours is caused by lack of oxygen in the compost due to overloading of food waste, and when the bin contents become wet. The solution is to stop adding food waste until the worms and microorganisms have broken down the initial feed and to gently stir up the entire contents to promote aeration. The drainage holes may be checked for blocking. If the drainage is insufficient additional holes can be drilled. Worms have been known to crawl out of the bedding if conditions are not favorable for them. If this migration is not triggered by moisture content of the soil, then the bedding may be acidic. Avoid adding citrus peels and other acidic foods to the bedding as these might reduce the pH of the bedding soil. One can overcome this acidic medium by adding a little garden lime and cutting down on acidic wastes.

In limiting the malodours, one should

-Reduce the amount of food

-Stir the bin thoroughly, especially at the bottom

-Add paper if the bedding is soggy

And if odours still persist, the best solution may be to start over, using new bedding, a minimal amount of scraps.