PH12012000194A1 - Earwig rearing composition, use thereof, method for rearing a predatory earwig, rearing system for rearing said predatory earwig and method for biological pest control on a crop - Google Patents

Abstract

The present invention relates to a novel earwig composition comprising a population of a predatory earwig and a factitious diet, which may be employed for rearing said predatory earwig species or for releasing the predatory earwig species in a crop. Also, the invention relates to a method for rearing a predatory earwig species, to the use of the earwig composition and to a method for biological pest control in a crop, which employ the earwig composition.

Description

Earwig rearing composition, use thereof, method for rearing a predatory earwig, rearing system for rearing said predatory earwig and method for biological pest control on a crop

FIELD OF INVENTION

The present invention relates to a novel earwig rearing composition for biological control of pests on crops, a method for rearing a predatory earwig species, a rearing system for a predatory earwig species and to the use of this rearing system for the control of crop pests. The invention also relates to a method for biological pest control in a crop employing the earwig composition according to the invention.

BACKGROUND OF THE INVENTION

Utilization of predatory earwigs as biological control agents has been investigated in the Philippines on three species, namely, Labidunia npana,

Euborellia annulipes (=Euborellia annulata) and Nala lividipennis for the control of corn borer in the field. Details in the biology are known in four species, namely, Euborellia annulipes, E. philippinensis, Nala lividipennis and

Proreus simulans. Mass-rearing of E. annulipes has been reported using artificial media (e.g dog food), as well as the biology and intrinsic growth rate of E. annulipes fed with dogfood. Biological investigation to harness the potential of the black earwig, Chelisoches morio (Fabr.) which successfully ; controlled the coconut buff mealybug infestation in commercially grown

Lakatan banana plantation in Indang, Cavite in 2008 have been done. Its high prey consumption rate indicates that C. mono has good potential as biological control agent. : :

Chelisoches morio (Fabr.) is a voracious feeder of aphids and mealybugs infesting bananas, as well as the coconut leaf beetle invasive to coconuts in the Philippines. The adult predator is winged and it can reach its target prey easily in the canopy by flight. The long duration of adult life and high reproductive potential are good attributes of this predator. The longer the predator lives the more pest preys it would consume, hence, the greater the control potential in the field. Likewise, the higher the number of egg batches the predator lays, the more progenies will be produced and consequently, the establishment of resident populations in the field is greater.

One of the most critical components to elucidate predator-prey relationships between a predatory insect and its prey is the availability of large numbers test materials. To determine the functional and numerical response of the predator, a ready supply of test materials of uniform stages and ages is required. For some predatory earwigs, rearing and maintenance is a simple task that involves transferring predators periodically from the stock culture to a fresh medium, and exposing them to laboratory conditions which support good growth and development. Other species, however, are less easily : cultured.

C. morio is one of these species. This predatory earwig (in addition to food) requires the presence of materials in which micro-environmental conditions protect them from dessication, direct light and cannibalism. It also requires substrate for oviposition/reproduction and brooding its eggs and hatchlings.

In addition, a cage that provides space so that the predators could freely move is an important factor for proper growth and development.

Cultures were established by repeated transfers of predators to zip-lock plastic cages, using its natural prey mealybug but success was variable. We ;

also tried the method used in rearing Euborellia annulipes, but the predators escaped easily once the rearing pans were opened during feeding.

The use of 1.5 li plastic bottle as rearing cages was tried but success was also variable because after several generations of rearing the culture got dense and bigger individuals tend to cannibalize smaller individuals, especially when food become limiting. A bigger jar was tried, but later this suffers the same set-back as the 1.5 li bottle. Rich stock of C. morio was produced after several months of rearing in these rearing units and maintaining them in hundreds of these cages become tedious and time consuming.

Large carton boxes were devised and provision for aeration and replenishing the food were provided on one side of the box. The use of carton boxes was sufficient but because these were made of paper these got soiled easily and depreciated early.

The plastic cages originally used in rearing spider mite and its predatory phytoseiid mite were tried, modified, and used conveniently to rear large number of C. moro.

Scientific literature reports several predatory earwig which prey on lepidopterous pests. Unfortunately, to date there are still no predatory earwig commercially available for biological control of lepidopterous pests and mealybugs/aphids. Despite the known predation of predatory earwig on mealybugs/aphids their usability as augmentative biological control agents : against mealybugs/aphids has not been recognized in the art. In augmentative biological control, biological agents are released in a crop for the control of a pest. Even more important, no economic mass-rearing systems, necessary for allowing the release of large numbers of the predatory earwig into a crop, which is of utmost importance for their usability as an ) augmentative biological control agent, are available in the art for those predatory earwig species which could potentially lower down population of mealybugs/aphids to non-destructive level.

Instead, mealybugs and aphids are controlled using chemicals which involve considerable investments not to mention hazards to the applicators and consumers as well as the environment.

DETAILED DESCRIPTION OF THE INVENTION

Biological control of mealybugs/aphids and other crop pests with predatory earwig which can be economically reared in large quantities on a factitious diet in a rearing medium would be very advantageous because such a rearing system uses a limited surface. Furthermore, in such a system rearing of the predatory earwig can be performed in laboratory conditions, which does not require large investments as compared to plant rearing in the greenhouses.

The prior art describes rearing of Euborellia annulipes with the use of a factitious diet, dog food. Dog food was used initially to rear C. mono. An important disadvantage of dog food is that it has to be pulverized prior to feeding to hatchlings which cannot consume big food particles. Older nymphal instars and even adults show preference to smaller particles of dog food.

Thus there is a need in the art for additional factitious diet which can be used for mass rearing beneficial earwigs such as the predatory earwig,

Chelisoches morio.

The predatory earwig species which are able to feed on both preys and i factitious diet particularly dog food or fish fry mash are omnivorous predatory i species. An omnivorous predatory earwig species is a predatory earwig species which is able to use both animal and plant food sources for its development (growth and reproduction). As such, the term omnivorous predatory earwig species in this specification includes a predatory earwig species, being able to prey on pests of crops as well as factitious diet as food sources for its development. Thus, the term omnivorous predatory earwig species is to be understood to mean a generalist predatory species.

A factitious diet is a food source used to rear the predator in the laboratory to replace natural preys, in which the predator is able to develop and reproduce such that the number f individuals in the rearing population can grow.

Predatory earwigs have their natural habitat on plants where they prey on insect pests and mites. They can be collected from their natural habitats.

Thus, the method according to the invention provides a new food source of earwig.

The composition according to the invention is not only suitable for mass- rearing of a predatory earwig. As it also comprises mobile preying life stages of a predatory earwig or life stages which can develop into these mobile life stages, it can also be employed as a biological crop protection agent.

In a preferred embodiment, the composition comprises a carrier for the individuals of the populations. The carrier can be any solid material which is suitable to provide a carrier surface to the individuals. Preferably, the carrier provides a porous medium, which allows exchanges of metabolic gases and heat produced by the earwig populations. Examples of suitable carriers are plant materials such as coir dustffiber, coconut leaves and soil combined with coir dust, 1:1 ratio. i ;

According to a preferred embodiment of the composition, the predatory earwig is selected from: the family of the Chelisochidae, such as from the

Genus Chelisoches, e.g. Chelisoches morio. This predatory earwig species may be considered as being generalist predatory earwig species.

For this species, rearing on a factitious diet has not been disclosed in the art.

The present invention discloses a factitious diet which can be used for economic rearing of C. mono, making it possible to use as an augmentative biological pest control agent.

In this specification, the term rearing must be understood to include the propagation and increase of a population by means of sexual reproduction.

A rearing population may comprise sexually mature adults from both sexes, and/or individuals of both sexes of other life stages, e.g. nymphs, which can develop to sexually mature adults. Alternatively, the rearing population may : comprise 1-6 females: 1 male. In essence, the rearing population is capable of increasing the number of its individuals by means of sexual reproduction.

Preferably the factitious diet, as defined above, is selected as fish fry mash which is commercially available in local market. Contrary to dog food, fish fry ~ mash does not need further pulverization prior to feeding, is cheaper and readily accepted by all life stages of the predator.

The relative amount of the factitious diet may depend on the specific intended use of the factitious diet and/or the stage of development of earwig population. In general where the amount of the factitious diet is offered in excess to the individuals of the predatory earwig are preferred for rearing of the predatory earwig species, so that sufficient food is provided to the ] predator. However, as the predator increases in size while feeding on the

] I factitious diet, the relative amount of the factitious diet will increase.

According to a further aspect, the present invention relates to a method for rearing the predatory earwig species. The method comprises providing a composition according to the invention and allowing individuals of said predatory earwig to feed on said factitious diet.

For an optimal development of the predatory earwig, the composition is maintained at 25-35 °C, preferably 25-30 °C. Suitable relative humidity ranges are between 75-90%, preferably 80-90%.

It is preferred that the composition comprises a carrier which can provide a porous medium for refuge to the predator for optimum growth and development.

According to a further aspect, the invention relates to a rearing system for rearing the predatory earwig.

The rearing system comprises a cage holding the composition according to the invention. The cage may be of any type which is suitable for restraining individuals of the predator. The rearing system may comprise means which i facilitate exchange of metabolic gases and heat between its interior and its i exterior such as aeration windows. Such aeration windows must not allow the 1 escape of individuals from the cage. This can be effected by covering the ] aeration windows with a fine mesh. .

The rearing system may be suitable for mass-rearing the predatory earwig ] species. Alternatively, the rearing system may also be used for releasing the predatory earwig in a crop. In this case it is preferred that the cage can be ;

rendered suitable to release mobile stages of the predatory earwig at a certain time. This can be effected by providing a closed opening in the cage which can be opened.

According to a further aspect, the invention is aimed at the use of the composition or the rearing system for controlling crop pests in a commercial crop.

The pest may be selected from, mealybugs, such as Dysmicoccus spp. and

Nipaecoccus nipae and aphids, Pentalonia nigronervosa. The predatory earwig Chelisoches mono has shown a good efficacy for controlling these pests.

The crop may be selected from, but is not restricted to banana.

The invention further relates to a method for biological pest control in a crop comprising of providing a composition according to the invention to said crop.

In the method according to the invention, the composition is provided by applying an amount of said composition on the crop at a per plant basis. The composition may be provided to the plant simply by spreading it on the base of the plant with the carrier as is common practice for employing predatory earwig for augmentative biological pest control. The number of the predator which may be provided to each individual plant by way of spreading may . range from 1-15, preferably 5-10 individuals. in the method for biological pest control according to the invention, it may not ] be necessary to provide the predator to all plants. The predatory earwig may / spread from one plant to another. The number of plants which must be ;

provided with the composition according to the invention in order to provide sufficient crop protection may depend on the specific circumstances and can be easily determined by the skilled person based on his experience in the field. Usually the number of predatory earwig released per hectare is more determining. This number may range from 1000-5000 or 5000-10000 per hectare.

In a further preferred embodiment of the method for biological pest control according to the invention the crop is selected as described in relation to the use of the composition.

The invention will now be further described with reference to the following examples, which show non-limiting embodiments of different aspects of the invention.

EXHIBIT 1

Oviposition Test of Chelisoches morio on factitious diet of fish fry mash

The objective of this experiment is to investigate on the reproductive capacity ] of female adults fed with the factitious diet from hatching until reaching the adult stage. :

The following were monitored on the breeding pairs of C. mono: 1) number of ] egg cluster laid, hatched and eaten, 2) duration in days in between egg i cluster laid, and 3) number of females that did not lay eggs. i

Materials and Methods

At the beginning of the experiment the Chelisoches morio adults were taken from mass cultures which started a few weeks earlier.

Reproductive capacity of C. morio was determined using 800 pairs which were paired in batches, with the following labels/codes: A1- A100; B1- B50;

C1- C100; D1- D100; E1-E100; F1- F100; G1- G100; H1-H100; and I1- 150.

Some provisions as soil/coir dust mixture, water and fish fry mash were provided per pair inside the 1.5 plastic bottle cages. When a cluster of eggs was laid, the plastic bottle cage was segregated from the batch and when the eggs hatched, the parental pair were removed together with the tag and transferred into another bottle. The nymphs were retained in the original container and provided water and fish fry mash until they were transferred into larger rearing cages like the carton boxes/sleeve cages and zipper- locked plastic cages.

Once the parental pairs were prepared, they were located in a cabinet inside a room with conditions set at 25-35 °C and relative humidity of 75-85%.

Every week data were obtained by evaluating the number egg clusters of all batches of paired adults. During which time, the provision for factitious diet and water was replaced with fresh one. Data gathering was terminated when adult females stopped laying eggs.

Results

In our breeding pairs, the first egg cluster laid by a female consisted of a smaller cluster and the biggest cluster was the second batch. Set A females ] (from 100 pairs) laid 215 egg clusters, accounting for about 8.7% of total egg ] clusters. Only one female did not lay eggs in the batch. Set B (50 pairs only) 1 laid 167 egg clusters, which is about 6.6% of total egg cluster laid. All females laid eggs. Set C (100 pairs), laid 378 egg clusters, accounting for about 14% !

total egg clusters but three females did not lay eggs at all. Set D (100 pairs), laid 384 egg clusters, which is about 14.2% of total egg clusters but three females did not lay eggs at all either. Set E (100 pairs) laid 399 egg clusters which accounts for about 14.8% of total egg clusters and all female laid eggs.

Set F (100 pairs), laid 347 egg clusters which is about 12.9% of total egg clusters; 3 females did not lay eggs. Set G (100 pairs), laid 331 egg clusters which accounts for 12.3 % of total eggs; 1 female did not lay eggs at all. Set

H (100 pairs), laid 332 clusters which is about 12.3 % of total eggs; 2 females did not lay eggs. The last set, |, (50 pairs), laid 146 clusters which accounts for 5.4% of total eggs; 3 females did not lay eggs. A total of 2,700 egg clusters were laid by C. morio females. Set A females ate about 49 egg clusters (22.8%); set B, 17 (10.2%); set C, 36 (9.5%); set D, 46 (11.95); set E, 23 (5.8%); set F, 29 (8.4%); set G, 27(8.2%); set H, 15 (4.5%); and set |, 22 (15.1%). A total of 264 egg clusters were eaten by female C. mono which is about 9.78% of the total egg clusters laid. Usually, females eat their fifth batch of eggs and this was attributed to old age. A total of 2,436 egg clusters hatched and at 30 individuals per cluster 73,080 progenies were produced.

C. mono females lay from 5-6 egg clusters per female throughout the reproductive period. The interval between the first and second batch of egg clusters varied and they are as follows: 11-57 days, (x= 25.29), for set A 1 females; 13-67 days, (x= 25.70) for set B; 11-62 days, (x= of 26.67) for set C; 13-36 days, (x= 22.26 for set D; 15-62 days, (x= 23.18) for set E; 15-48 days, J (x= 23.09) for set F; 13-47, (x= 24.44) for set G; 14-43 days, (x= 22.13) for set H and 15-49 days, (x= 24.26) for set | females. The interval between the second and third cluster differed slightly from the first and second and this holds true for the succeeding batches. The females remained reproductively ; active for about 43 days for set A; 65 days for set B; 76 days for set C; 69 days for set D & E; 65 days for set F; 63 days for set G; 59 days for set H; and 62 days for set |.

The results show that Chelisoches morio has high reproductive potential on factitious diet such as fish fry mash.

EXHIBIT 2

Mass Rearing of Chelisoches morio on factitious diet.

C. morio is reared in cages (for example 8-12 oz. plastic cups, 1.5 li plastic bottles, carton boxes, sleeve cages, and zipper-locked plastic cages). The cages were provided with sufficient aeration to ensure optimal exchange of gases with fine mesh muslin cloth. A layer of 5 to 10 cm of mixed soil and coir dust (1:1) is used as carrier.

The carrier layer should not be too thick to ensure optimal exchange of gases and heat. At least once every week, the factitious diet is replaced with fresh ones.

The quantity of factitious diet to be added is measured based on the number and life stage of the predatory earwigs present in the rearing cage. Optimally, 1 g/8-12 oz. plastic cup, 5-10 g/ 1.5 li plastic bottle, 15-20g/carton box or sleeve cage and 30-50g/zipper-locked plastic cage. The culture is kept at a temperature between 25-35 °C, a relative humidity of 80 to 90% in the rearing cage. In this way a rearing population of C. mono can complete development in 4-5 weeks. ]

EXHIBIT 3 i

Field Releases of Chelisoches mono ]

;

Field releases of C. morio have been done in farmer's field in 3 provinces (Sta. Cruz , Laguna; Indang, Cavite and Quirino). Before predator release, the population of both the predator and prey, mealybug/aphids were monitored after which appropriate stage/number of predators were released. Population build-up of both predator and prey were monitored regularly. The specific field releases are shown below:

A. Barangay Labuin, Sta. Cruz, Laguna

Field releases of C. mono were done in the farmer's field in Barangay Labuin,

Sta. Cruz, Laguna. The predominant mealybug pest in this site is N. nipae. C. morio was released at 10 individuals per plant. All the 642 banana plants 1 were inoculated. Five rows were selected as sampling row, designated R1 to

R5. Ten plants per row were randomly selected and tagged. For the first row, the first sampling unit was tagged R1-1, up to R1-10. For the second row, R2- 1 to R2-10; for the third row, R3-1 to R3-10 and so on. After the plants were tagged, the population level of N. nipae was quantified per leaf but all the infested leaves per plant were rated. The rating was started from the lowest leaf going to the youngest leaf. The rating scale used was as follows: 0- no colonies; 1-few colonies (1-20); 3-few to moderate colonies (30- 70); 5-moderate colonies (80-150); 7-moderate to many colonies (160- 300); and 9-many colonies (more than 300).

To get the rating per plant, individual rating per leaf of all infested leaves are 1 added and then divided by the number of infested leaves. And to get the over- all rating, individual plant rating are added and then divided by the total i number of sampling units, i.e. 50 plants. i

Every two weeks, sampling was done. The predator was monitored per tagged plant by counting the number of adults, egg cluster, and nymphal instar by stage. Also, other organisms that prey on C. mono were also noted/recorded, along with other potential prey in the field.

B. Barangay Tambo- llaya, Indang, Cavite

The second field release was done in Barangay Tambo-llaya, Indang, Cavite, : where the planting materials used were suckers from the first cooperating site. In the first site about 7,000 predators were released, at the rate of 10 predators per plant, while, in the second site, about 2000 predators were released, using the same rate of 10 predators.

Predators intended for release in the field were collected from plastic rearing cages and concentrated in plastic jars. In the field, the predators were released per plant. Sampling was done before predator release and at predetermined interval after predator release.

The predominant mealybug pest in banana in the second site was also N. nipae. The same procedure and data gathering as in the first site was followed. Likewise, data gathering is on-going and results will be reported later. Also, a plastic cage was brought to the site and about 1000 stock for rearing was given to the cooperator. This was intended for possible extension of the rearing protocol to intended clients/users.

C. Brgy. Cajel and QSAC Experimental Farm Diffun, Quirino

The third site was in Barangay Cajel, Diffun, Quirino. Predators (31-4" instars) were released at the rate of 10 predators per plant, while 50 plants per site were monitored. The predators were counted based on life stages 3 while the prey mealybugs were rated using the rating scale used in Sta. Cruz,

Laguna and Indang, Cavite. ]

Results

From an initial mealybug rating of 3.3, where C. morio was released, the rating was down to 2.9 and the counts of the predator was 74,47% were adults while 41% were 1% instar while the rest and the remaining percentage consisted of eggs and 2™ instar. This was expected because the initial population released in the field 3 weeks before consisted of young adults reared in the laboratory which apparently laid eggs as soon as they were released and this hatch successfully and later monitored. Thereafter, counts of the predator decreased until the 4" sampling week with a corresponding increased in mealybug rating. The lower number of the predator counts was attributed to spraying done on mango trees infested with mango hoppers; deleafing of old leaves which coincided with hot and dry conditions; and red fire ants. A second release was done resulting to a higher count of the predator in the next sampling. However, on the subsequent sampling, the predator count declined consistently up to the last sampling time before a strong typhoon which toppled down all the banana plants. The results indicate that the predator failed to establish fully in this farm for reasons already mentioned.

The predominant mealybug pest in Cavite was N. nipae. Higher counts of the predator were monitored coinciding with high rating of mealybug in the 1° release site. There was lower count of the predator on the next sampling, with a corresponding lower rating of mealybug. The results show that the predator was able to control the mealybug. In 2" release site, there was an increasing count of the predator and the prey mealybug N. nipae failed to increase in number as indicated by low rating. In general, C. morio showed better performance in indang Cavite which can be attributed to the following;

cooler weather than in Sta. Cruz, Laguna; no red fire ants that prey on C. morio; and the cooperator did not spray insecticide.

In Quirino, C. monio was able to establish in the 3 sites despite very low rating of mealybug. This is attributed to presence of other pests like lace wing bugs and termites which served as prey to C. moro in the absence of prey mealybug.

Claims (11)

CLAIMS:

1. An earwig rearing composition comprising of a rearing population of a predatory earwig species, a factitious diet comprising of commercial formulation of dog food and fish fry mash, and optionally a receptacle for said diet.

2. The composition according to claim 1, wherein the phytoseiid predatory earwig species comprises at least one species from the family Chelisochidae of the Order Dermaptera.

3. A method for rearing a predatory earwig comprising of providing a composition according to claim 1, and allowing individuals of said predatory earwig to feed on said factitious diet.

4. A method according to claim 3, wherein the composition is maintained at 25-30°C or 75-95% relative humidity, or both.

5. A method according to claim 3, wherein said composition comprises a receptacle and a suitable food substance which is replenished on a weekly interval in the receptacle.

6. Rearing system for predatory earwig comprising a cage holding the composition according to claim 1.

7. Rearing system according to claim 6, wherein said cage comprises a zipper-locked exit for at least one mobile life stage of the phytoseiid mite.

8. A method for controlling mealybugs and aphids in a crop comprising of providing a composition according to claim 1 to said crop.

9. The method according to claim 8, wherein the amount is from 1-10 individuals belonging to the third nymphal instar, fourth nymphal instar and adult stages.

10. The method according to claim 8, wherein the crop is banana (lakatan and saba).

11. The method according to claim 8, wherein the pest is Dysmicoccus neobrevipes, Nipaecoccus nipae and Pentalonia nirgonervosa. ”