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Cryptaspasma sp. (Lepidoptera: Tortricidae: Olethreutinae)

Prepared by Mark S. Hoddle,

Department of Entomology, University of California, Riverside, CA 92521 USA

• Introduction 
• Pest Identification and Developmental Biology
• Eggs and Oviposition
• Larvae
• Pupae
• Adults
  
• Feeding Damage
  
• Natural Enemies of Cryptaspasma sp.
  
• Establishing and maintaining a Cryptaspasma colony
  
• References 

Cryptaspasma spp. Walsingham (Lepidoptera: Tortricidae) belong to one of the most primative tribes in the sub-family Olethreutinae, the Microcorsini. This genus is composed of around 33 species that are found in the neotropics, the southeastern USA, Japan, eastern Russia, Africa, Madagascar, New Zealand, and Australia (Brown and Brown 2004). Very little is known about the ecology and biology of Cryptaspasma spp. Known food plants include acorns of Quercus spp., seeds of stone fruits, macadamia nuts, and fruit of aceitunillo (Aextoxicon punctatum [Aextoxicaceae]). In the Lauraceae, hosts include, the fruit of Belschmiedia pendula, Persea borbonia (red bay), P. palustris (swamp bay), and P. americana (avocado) (Brown and Brown 2004).

Cryptaspasma spp. have been reared from avocado seeds collected in Puerto Rico, Mexico (Michoacán), and Guatemala. The pest status of Cryptaspasma spp. infesting avocado fruit in Mexico (i.e., C. lugubris) is uncertain as larvae have been found in seeds removed from fruit that had been collected from the ground. In Guatemala, C. sp. nr. lugubris (referred to hereafter as Cryptaspasma sp.) was reared from avocados collected across multiple locations. However, fruit picked from trees and collected from the ground at study sites in Guatemala was commingled making it impossible to determine of larvae had infested fruit hanging in trees or had attacked fruit lying on the ground. However, this moth was reared from recently picked avocados that were being sold along the side of the road in Santiago Atitlan in Guatemala (see below).

Since Cryptaspasma sp. has been reared from fruit collected from the ground in Mexico (Brown and Brown 2004) this finding suggests one of two possibilities: (1) avocados lying on the ground and collected for rearing studies had been prematurely aborted because of larval feeding damage within fruit that were originally hanging on trees, or (2) Cryptaspasma sp. females only oviposit on avocado fruit that have dropped to the ground because of other reasons (e.g., strong winds caused fruit to fall off tree prematurely) or ovipositing females utilize bare avocado seeds that have been exposed once protective flesh has been removed (i.e., eaten by animals or rotted away).

Eggs and Oviposition: The eggs of Cryptaspasma sp. are laid in masses and individual eggs are flat somewhat irregular in shape and white in color when first laid, but turn grey as larvae approach eclosion. Examination of the placement of 633 eggs in 30 randomly selected egg masses laid by Cryptaspasma sp. in the laboratory revealed that the average egg mass size was 21.10 ± 3.52 eggs (range 2 to 73 eggs), and that ~80% of eggs were laid on smooth plastic which included clear plastic cups and lids holding avocado seeds or fruit, and the floor and walls of the Bug-Dorm used for ovipositional studies. The remaining ~20% of eggs were distributed evenly across seeds and fruit in the cage. At 22.14^oC ± 0.13 it took 10.78 ± 2.53 days for Cryptaspasma sp. eggs to hatch.

Eggs of Cryptaspasma sp. (above and left to right) laid on a clear smoot plastic cup, an avocado seed, and the skin of a mature avocado fruit.

Larvae: Upon hatching, Cryptaspasma sp. larvae bore quickly through the skin of avocado fruit and tunnel into seeds where they complete larval development. Evidence of first instar larval tunneling into fruit is readily discerned by the detection of very fine "dust-like" frass on the outsides of fruit. Larvae emerging from eggs laid on plastic readily bore into clean avocado seeds that are adjacent to egg masses and a single avocado seed can support as many as 5-8 Cryptaspasma sp. larvae. In the laboratory at 22.14^oC ± 0.13 it took Cryptaspasma sp. larvae around three weeks to complete development and emerge from seeds in search of pupation sites. Of 301 larvae reared on avocado seeds in the laboratory 72% reached adulthood. 

Above (left) Cryptaspasma sp. larva on an avocado seed, larval tunneling damage to an avocado seed (center), and mature larvae (right) that have emerged from an avocado seed and have begun the "wandering" phase. Mature Cryptaspasma sp. larvae search of pupation sites for less than a day before entering a prepupal stage within the protection of a pupal chamber that is lined with fine loosely spun silk. Larvae in seeds and those searching for pupation sites are extremely aggressive towards conspecifics and will engage in biting and writhing when contacts are made.

Pupae: In the laboratory, mature Cryptaspasma sp. larvae readily formed pupal cells between layers of paper towel that line the floors of rearing boxes. Occassionally, larvae would force their way between layers of paper fibers that comprised a single sheet of paper towel and form pupal cells between the upper and lower sides of a piece of paper towel. At this stage of development, larvae are very sensitive to disturbance. Premature seperation of paper towels before the pupal case has been formed can result in larvae abandoning pupal chambers and commencing walking again. Larvae that were very close to pupating and unable to walk could die of dessication following the disturbance of the pupal chamber. The prepupal stage is variable in duration and may be affected by the fitness of the larva. Smaller malnourished larvae appear to take longer to form pupae in comparison to larger healthier larvae and smaller larvae may be more likely to die following disturbance. Approximately 95% of mature larvae would abandon avocado seeds to locate pupation sites, the remaining 5% of larvae would pupate within feeding tunnels in avocado seeds. Casual observations in the laboratory at 22.14^oC ± 0.13 suggest that the sedentary prepupal stage lasts around 2-4 days (depending on the status of the larva) and the pupal stage is around 8 - 12 days in duration. When adult moths emerge, the pupal case is forcibly discharged from the pupal cell and will protrude from the margin of the pupal cell within which pupation occurred. Pupae are very sensitive to contact and vigorously flick the abdomen when disturbed or touched.

Mature avocados placed on the ground in a coffee plantation with an avocado tree overstorey. Cryptaspasma sp. had been reared from avocados collected from this site. After 3-6 days on the ground animals had consumed a significant amount of skin and fruit pulp. Any Cryptaspasma sp. eggs laid on the skin or exposed pulp of fruit would have been accidentally consumed before hatching.

Assuming that Cryptaspasma sp. does lay eggs on the skin or pulp of dropped fruit in the field as indicated by laboratory results, it is reasonable to suggest that under prevailing field conditions the majority of these eggs would be consumed by animals eating dropped fruit on the ground before eggs had procured sufficient degree-days to hatch and for larvae to bore through fruit pulp before tunneling into protective seeds.

Therefore, laying eggs on the skin or pulp of dropped avocados lying on the ground would be appear to be a maladaptive reproductive strategy for Cryptaspasma sp. because of risk from accidental predation and may therefore be unlikely to occur. Eggs oviposited on exposed seeds on the ground would be at less risk of accidental predation by vertebrates consuming fruit and could be a viable reproductive strategy as rapid destructive seed consumption by vertebrates was not observed in the field.

Rearing of Cryptaspasma sp. from Purchased Avocados. Support for Cryptaspasma sp. ovipositing on avocados hanging in trees came from the purchasing of 354 fruit from a local roadside vendor who had harvested avocados from backyard trees in Santiago Atitlán on the day they were purchased. Examination of purchased fruit in the laboratory failed to detect any rotten, cracked, or otherwise damaged avocados (damage of this nature would have been indicative of fruit being damaged upon hitting the ground after dropping), which strongly suggested that these fruit had not been collected from the ground, and were recently picked from trees as claimed. Cryptaspasma sp. was reared from these purchased fruit suggesting that females had oviposited on fruit hanging in trees.

Freshly picked fruit purchased from roadside vendors in Guatemala yielded Cryptaspasma sp. Purchased fruit were held in the laboratory for ~14 days before seeds were extracted and held individually in ventillated rearing cups for larvae to emerge and pupate.

Future Studies to Investigate the Oviposition Behavior of Cryptaspasma sp. in the Field. The obvious way to determine if Cryptaspasma sp. is a pest of avocados hanging on trees is to harvest fruit directly from trees for rearing and not to commingle picked fruit with those collected from the ground. Direct fruit harvesting to address this question was attempted as part of this project on Cryptaspasma sp. in March 2007 but was unsuccessful. There were two possible reasons why Cryptaspasma sp. was not reared from picked fruit from sites that had yielded this moth from earlier surveys. First, by March when picked fruit surveys for Cryptaspasma sp. were initiated, the dry season in Guatemala was well underway and this climatic change was accompanied by a noticeable decrease in the collection of this moth (i.e., complete lack of detection). This seasonal transition was accompanied by an increase in the detection frequency of another seed feeding moth in fruit, Stenoma catenifer. Second, post priori analysis of collection data suggests that in addition to time of year, altitude may be important in determining the distribution of Cryptaspasma sp. in Guatemala. This tortricid was only reared from avocados that were collected at altitudes exceeding 1,300 m and it co-existed with S. catenifer up to 1,592 m, above 1,609 m only Cryptaspasma sp. was reared from avocados. Conversely, S. catenifer was reared from avocados grown in hot and humid conditions at sea level up to 1,592 m and the prevalence of this moth at higher altitude sites increased as the dry season progressed.

One species of endoparasitoid, Pseudophanerotoma sp. (Hymenoptera: Braconidae: Cheloninae), was reared from ~30% of field collected Cryptaspasma sp. larvae. This is the first host record for a Pseudophanerotoma sp. Members of the Cheloninae are generally egg-larval parasitoids of tortricoids and pyraloids.

Cryptaspasma sp. pupae removed from pupal cells between layers of paper towel. These pupae can be easiy sexed and divided for maintaining colonies or used for experiments.

Brown, J. W. and R. L. Brown. 2004. A new species of Cryptaspasma Walsingham (Lepidoptera: Tortricidae: Olethreutinae) from Central America, the Caribbean, and southeastern United States, with a catalog of the world fauna of Microcorsini. Proc. Entomol. Soc. Wash. 106: 288-297.