Photo-Selective Nets and Pest Control: Searching Behavior of the Codling Moth Parasitoid Mastrus ridens (Hymenoptera: Ichneumonidae) under Varying Light Quantity and Quality Conditions

Photo-selective nets (PSN) are used to manipulate the physiology of fruit crops. Besides their advantages to the crop, PSN potentially affect insect pests and their natural enemies. We aimed to assess the effects of these production systems on the searching behavior of the codling moth parasitoid, Mastrus ridens. We hypothesized that PSN and black standard nets (SN) affect the behavior of the parasitoid by delaying host localization and reducing parasitism. Laboratory experiments were carried out in closed cages under four treatment conditions: black SN, pearl PSN, red PSN, and no PSN as control (uncovered cages). Our results showed that the host localization of M. ridens was delayed under black SN and enhanced by pearl and red PSN. The PSN and the black SN did not affect the parasitism levels. In addition, the initial behavior of the parasitoid during the first 30 min of the bioassays was not affected by treatments. However, females spent most of the time walking around the arena, grooming, or resting, regardless of the color of the net. Parasitism was not affected under the PSN or the black SN; however, this must be verified in field conditions.

Parasitoids associated with codling moth (Cydia pomonella) in apple-growing regions in New Zealand

Codling moth (Cydia pomonella) (CM) is a major pest of apples in New Zealand. Several biocontrol agents introduced in the past to control CM have only been partially successful at reducing CM populations, so a parasitoid wasp, Mastrus ridens (Hymenoptera: Ichneumonidae), was recently released into apple-growing regions. This study sought evidence of the establishment of CM parasitoids. Corrugated cardboard bands (2-cm wide bands with sentinel CM larvae and 10-cm wide empty bands to trap wild CM larvae) were used to assess the presence of M. ridens and other CM parasitoids in Hawke’s Bay, Nelson, Central Otago and Waikato regions. Five CM parasitoid species, including M. ridens, were recovered from sentinel and wide bands. Liotryphon caudatus (Hymenoptera: Ichneumonidae, released to control CM in 1906) was found in Hawke’s Bay and Waikato. Ascogaster quadridentata (Hymenoptera: Braconidae, released to control CM in the 1930s), Glabridorsum stokesii (Hymenoptera: Ichneumonidae, released in 1967 to control light brown apple moth), Dibrachys microgastri (Hymenoptera: Chalcidoidea: Pteromalidae, an accidental arrival) and M. ridens were found in all regions. The interspecific competition between M. ridens and other parasitoid species remains to be investigated.

Longevity and fecundity of laboratoryreared Liotryphon caudatus an ectoparasitoid of codling moth

Liotryphon caudatus was introduced into New Zealand to control codling moth (CM; Cydia pomonella) in the early 1900s As part of ongoing research into the biological control of CM a laboratory colony of L caudatus was established from fieldcollected adults reared on diapausing CM larvae The longevity and fecundity of laboratoryreared L caudatus adults were measured at 231C and 16 h photoperiod Longevity in a nonhost environment was measured by holding a newly emerged female and a male in a container with water and food Survival of 18 pairs was monitored daily The food and water in the containers were refreshed regularly The fecundity and the longevity of females were measured by providing five diapausing CM larvae to each of nine mated females (age 710 days) in a similar container with food and water The CM larvae were replaced every 48 hours until the females were dead In the interactions between L caudatus and Mastrus ridens a recently released gregarious ectoparasitoid of codling moth in applegrowing areas where L caudatus has already established

Interspecific competition between Mastrus ridens and Liotryphon caudatus ectoparasitoids of codling moth Cydia pomonella

Mastrus ridens is a gregarious ectoparasitoid and Liotryphon caudatus is a solitary ectoparasitoid of cocooned codling moth larvae These two parasitoid species could potentially compete for resources because they oviposit and develop on the same lifestage of their host Competition experiments in the laboratory showed that females of both species oviposited into host cocoons regardless of previous parasitism but adults of only one species ever emerged Liotryphon caudatus larvae were highly aggressive They preyed upon eggs and larvae of M ridens as well as conspecifics such that only a single adult L caudatus emerged Mastrus ridens larvae survived competition with L caudatus if they had a sufficient time to develop to a size that could attack L caudatus eggs However L caudatus was often still able to outcompete M ridens even when M ridens eggs were laid first Mastrus ridens hyperparasitised L caudatus larvae that had themselves cocooned within the host cocoon but no parasitoids emerged Liotryphon caudatus outcompeted M ridens in an enclosed space but that ability in a natural ecosystem remains to be investigated