Learn about the pests that damage mushroom and its control.
1. Sciarid Fly, Bradysia Tritici (Coquillet) (Diptera: Sciaridae):
Identification:
The adults are small, delicate, greyish black, two winged insects measuring 2.5- 3.0 mm in length with conspicuous bead-like antennae. Females have a pointed abdomen that is frequently swollen with eggs, while males have prominent claspers at the end of their abdomen. The larvae (maggots) are dirty white with black head and are 6.5 mm long.
Life-History:
The females lay eggs on compost, casing and mushroom in clusters of chain. The eggs are small, 1.5 mm long, oval and translucent white. The larvae hatch from the eggs after about 4-6 days. The larvae feed on decaying organic matter, mycelial attachments below casing and at the spawning surface. The larvae transform into pupae after about 20 days and pupation generally lasts about a week. The insect completes its life-cycle in 26-28 days. There are five generations during the cropping period.
Damage:
The larvae feed on mushroom, enter from the stem end and move towards the cap portion. The most serious injury is, however, caused to the developing pin-heads, which turn yellowish brown and never develop into normal mushrooms. Very high numbers of larvae feeding in the compost during spawn run can also inhibit fruit body production through destruction of the compost and the mycelium. The incidence of this pest starts in the first week of February and reaches its peak in the second week of March, with an overall average infestation of 40 per cent.
Control:
(a) Preventive Measures:
(i) Compost should not be prepared directly on soil surface.
(ii) Sterilization of compost should be done at 60°C to kill insects which come through compost.
(iii) Screen room exteriors or interiors with nylon net of 35-40 mesh size.
(iv) The trap consisting of 15 watt bulb and polythene sheet (50 × 75 cm) coated with white grease and then hanged over the wall below bulb during second fortnight of January in mushroom houses is most efficient in reducing the fly population.
(v) Mix the compost thoroughly at last turning after spraying 15-20 ml of chlorphriphos 20EC or 100 ml of Nimbecidine 0.003% in 20 litres of water. This quantity is used for the compost prepared from 100 kg of wheat/paddy straw. If the flies are present in the mushroom house before casing, mix thoroughly 10 ml of chlorphriphos 20EC in 4-5 litres of water in 100 kg of ready to use casing material before its use.
(b) Remedial Measures:
Spray premises with dichlorvos 100EC at the rate of 6 ml per 10 litres of water on window panes, walls and ceiling of mushroom house. After spraying, close the mushroom house for 2 hours. Observe an interval of 48 hours between spraying and picking of mushrooms. Direct spraying on beds should be avoided.
2. Phorid Fly, Megaselia Halterata (Loew) (Diptera: Phoridae):
Identification:
The adult flies are small, hump-backed and light to brown in colour. The adults are two winged flies, measuring 2-3 mm in length and the bristle like antennae are inconspicuous. They appear stockier than sciarid flies, and are very active, running and hopping with quick and jerky movements. The larvae are dirty white maggots, 3.5 mm long with narrow head and visible blackish mouth hooks.
Life-History:
The female flies lay about 50 eggs, which are very small, elongated, cylindrical and whitish. They prefer spawned compost and gills of opened mushrooms for egg laying. The larvae after hatching directly bore into the mushroom cap, whereas those hatching from the eggs laid on spawn-run compost or casing, tunnel through the lower end of the mushroom stalk. Mature larvae come out of the mushroom and pupate in the casing or compost or sometime in mushrooms.
The pupae are about 2-3 mm long and gradually turn from cream coloured to dark brown as they mature. The development from egg to adult takes 14-16 days. The insect becomes active during September to November and again from second half of February till the end of the cropping period. The severe winter is passed as hibernating pupae when pupal period is prolonged upto 50 days.
Damage:
The maggots feed gregariously on mushroom, starting from the stalk and moving upward into the cap forming tunnels in the stalk. The attacked mushrooms turn yellowish brown to brownish, and when attacked at pin-head stage, the development is restricted. The adult flies are capable of transmitting fungal and bacterial diseases. Since they are active fliers, phorid flies can be a significant irritant to picking crews.
3. Cecid Fly, Heteropeza Pygmaea Winnertz (Diptera: Cecidomyiidae):
Identification:
These are tiny flies and orange black in colour. The cecid fly larvae are white legless maggots, about 2 mm long and bluntly pointed at both ends. The head and tail are not easily distinguished except by the direction of travel.
Life-History:
The adults of cecid flies are rarely seen because under most conditions, larvae become ‘mother larvae’ giving birth directly to 10-30 daughter larvae. This species usually does not become a pupa and subsequent adult that must mate before laying eggs.
Reproduction is accomplished without mating and gives rise to daughter larvae directly (paedogenesis). When conditions are optimal, this method of reproduction can result in very rapid multiplication of this pest, leading to very large number of larvae, tens of thousands per square metre.
Damage:
Larvae are the damaging stage which feed on mycelium and cause damage to stalk and gills. Brown coloured stripes can be seen on the stipe and gills. Initial infestation of cecid fly may take place by transport of infested peat or substrate. As the maggots are sticky, they might spread through trays, tools, clothes, shoes, etc. of the workers. Small infestations may not be readily apparent at first.
If large populations develop, the larvae may mass together on the floor and disperse in large groups. Larvae can also be found on mature mushroom caps packed for market. This species has the potential to significantly reduce yield, when it becomes established on a farm. Damage to mushrooms has been recorded to be as high as 50 per cent due to this pest.
4. Springtail, Seira Iricolor Tosii & Ashraf (Colembolla: Entomobryidae):
Identification:
Springtails are tiny, 1 mm long, silver coloured, stout, having long tails. They are so named because they have forked structure or furculum with which they jump. The furculum arises on the ventral side of the fourth abdominal segment. During rest period, the furculum is folded forward under the abdomen.
The adults are of ground colour with light violet band along sides of the body. Intensely dark and rounded scales are present all over the body. The mouth parts are elongate and stylet like and are concealed within the head. Antennae are short and with a few segments.
Life-History:
Eggs are laid singly or in small groups on paddy straw pieces. A female lays 9-16 eggs which hatch in 5-20 days. The pre-reproductive period is 10-15 days and adult longevity is between 22-30 days. S. iricolor is active throughout the year on button, oyster and paddy straw mushrooms.
Maximum activity occurs during July-August on tropical mushroom (Volvariella volvacea). In the absence of mushrooms, S. iricolor survives on moist organic matter near mushroom houses. They are active in the dark and remain hidden either under the casing soil compost or fruit bodies and move by springing several centimetres, when disturbed.
Damage:
Both nymphs and adults feed on mycelium and destroy planted spawn. They also attack stalks and caps. They are found in straw, compost and casing layer. Oyster mushroom is most preferred.
Control:
(i) Follow proper sanitation and pasteurization.
(ii) Crop should be raised above the ground level.
(iii) Never use spent compost.
(iv) Spray malathion 50EC at 0.05% on the infested place.
(v) Use diazinon 20EC @ 15 ml in 100 kg wheat straw compost.
5. Nitidulid Beetle, Cyllodes Indicus Grouvelle (Coleoptera: Nitidulidae):
This is a serious pest of oyster mushroom. Female lays eggs singly between the gills. Grubs are the damaging stage which feed between gills and then on stipes of mushroom, making them hollow.
Control:
(i) Over matured mushroom should not be left unharvested.
(ii) Apply bleaching powder to repel these beetles.
6. Mushroom Mites, Pigmophorus Spp. (Prostigmata: Pyemotidae), Tarsonemus Spp., (Prostigmata: Tarsonemidae), Tyroglyphus Spp. (Stigmata: Acaridae):
Sixty species of mites have been found associated with mushrooms worldwide. However, in India only 8 species have been identified to be economically important. The mushroom mites are0.3 to 0.5 mm long, i.e., pin head size and varying in colours. The saprophagous mite, Tyrophagus putrescentiae (Schrank), is the most damaging species of mite occurring in Himachal Pradesh, Delhi, West Bengal and other states.
Life-Cycle:
The mites are present in compost and migrate to casing material. They enter into mushroom bed via flies, on which the migratory stages of mites are clung by means of suckers. Female lays about 100-200 eggs. Fertile eggs develop into females and unfertile ones into males. Life-cycle lasts for 10 days at 20-30°C. Prolonged summer temperature increases the population.
Damage:
The mites feed on the mycelium and damage sporophores by causing shrunk caps and brown rusted spots on buttons. Buttons are sometimes hollowed out or cavities appear in on stalks and caps. They may completely destroy the young buttons of mushrooms, when attacked at early stage of development.
Control:
(i) Pasteurize comport and casing material properly.
(ii) Maintain strict hygienic condition in and around mushroom house.
(iii) Disinfect mushroom houses by kelthane 50EC at 0.01% on the mushroom beds during cropping in case of mite infestation.
(iv) Sterilize compost at 60°C to kill pests which come through compost.
(v) Burn sulphur in empty mushroom houses.
(vi) All infested and decaying mushrooms should be removed and destroyed to prevent further increase of pest population.
7. Mushroom Nematodes, Ditylenchus Spp. (Tylenchida: Anguinidae) and Aphelenchoides Spp. (Aphelenehida: Aphelenchoididae):
The nematodes encountered in mushroom compost/beds have been categorized as myceliophagous, saprophagous predaceous, plant parasites and animal parasites on the basis of their nature of parasitism. Among these, only myceliophagous and saprophagous forms hold significance as they effect the crop yield through direct feeding or indirectly.
Predeaceous forms usually occur in low counts and are beneficial as they feed upon the harmful myceliophagous and saprophagous nematodes. Plant and animal parasitic nematodes rarely prevail in small numbers, merely as contaminants.
Myceliophagous nematodes have often been observed to infest the mushroom beds and reduce productivity of compost and its market value. Nematodes have often been observed to infest the mushroom beds and reduce productivity of compost and its market value.
Nematode infestation in mushroom is unique in a way that the mushroom nematodes have not only adapted themselves fully with ecological requirements of the crop and multiply very fast to occur in high number in mushroom beds, but these are only examples of ectoparasitic forms, capable of inflicting 100 per cent crop losses.
These are small microscopic thread like organisms which can be found in almost any type of environment, all types of soils and areas, where organic matter is found and are capable of rapid multiplication. The myceliophagous nematodes are the ones which suck the mycelial sap and leave it devitalized.
Till today, six genera, two belonging to order Tylenchida (Ditylenchulus spp. and Pseudhalenchus spp.) and four belonging to order Aphelenchida (Aphelenchoides spp., Aphelenchus avenae, Paraphelenchus spp. and Scinura spp.) have been found to be associated with mushroom cultivation.
Among tylenchids, the predominant is Ditylenchus myceliophagous Goodey, and among aphelenchids, Aphelenchoides with 20 species reported from mushroom farms located globally are the most significant species. Out of these, 10 species have been reported from India, including A. compositicola Franklin, A. sacchari Hooper and A. agarici Seth & Sharma.
Life-Cycle:
Aphelenchids, showing a mycelophagous behaviour, generally have a short life- cycle of 7-12 days, with temperature playing the major role. It has been reported that A. composticola took 18 days to complete its life-cycle at 13°C; it was completed in 10 and 8 days at 18 and 23°C, respectively.
The mean sex ratio was found to be 0.69 and was always less than one, the number of females being always more than males. The developmental period of A. sacchari from egg to egg has been reported to be 12 days. The longevity of females and males was 35-80 and 35-100 days, respectively.
A. agaricus is known to complete one life-cycle in eight days at 28°C. It is bisexual species with an average female to male sex ratio of 1.5: 1. The average life span of females and males, with sufficient food availability, was 89 and 100 days, respectively. However, the females in water survived between 19-32 days.
Damage:
Myceliophagous nematodes (which feed on mycelium) are known to be the most damaging. They have needle like stylet on their mouth part, with which they penetrate and puncture the mycelial cell. These nematodes suck the sap and leave the cell devitalized. After feeding upon one cell, the nematode shifts to another with the help of moist film present in the compost. The cell sap oozed out due to leakage from the damaged hyphae may also assist the nematode movement from one cell to another.
The myceliophagous nematode affected beds show various types of symptoms like mycelium disappearance, browning and stunting of water soaked pinheads and the fruit bodies appear in patches. The compost emits a particular odour and yield declines drastically.
Control:
(i) Maintain strict hygienic conditions in the growing rooms by providing doors fitted with fly proof wire mesh and complete sanitation around the mushroom farm.
(ii) The peat heat temperature during pasteurization must be maintained at 58-59°C for four hours.
(iii) The casing soil should be sterilized properly either with steam heat (65°C) or with formatin.
(iv) Wooden trays should be sterilized properly either with steam, formalin or dipped in hot water (80°C) for 2-3 minutes.
(v) Growing of nematode-resistant strains in rotation with the crop of common white button mushroom helps to reduce the inoculum level of the nematodes in the mushroom house.
(vi) The nematode trapping fungi like Arthrohotrys spp. can be used as biological control agents for controlling mushroom nematodes. The fungus traps the nearby nematodes and kills them.