The effect of floral resources and mealybug honeydew on the longevity of Anagyrus fusciventris (Girault) (Hymenoptera: Encyrtidae), a parasitoid of both the longtailed (Pseudococcus longispinus Targioni Tozzetti) and citrophilus mealybugs (P. calceolariae Maskell) (Hemiptera: Pseudococcidae) in New Zealand, was investigated in the laboratory. A. fusciventris longevity was significantly increased by the provision of sugar solution, buckwheat (Fagopyrum esculentum) and alyssum (Lobularia maritima) flowers, and P. calceolariae honeydew compared with water alone. Female A. fusciventris provided with buckwheat survived 17 days longer than females provisioned with water alone.

Grapevine leafroll disease (GLD) affects grapevines worldwide. The primary causal agent of GLD is grapevine leafroll-associated virus 3 (GLRaV-3), which spreads to uninfected grapevines via mealybugs and soft-scale insects. Pseudococcus calceolariae (Hemiptera: Pseudococcidae) is a mealybug vector of GLRaV-3 in New Zealand. P. calceolariae also colonizes clovers (Trifolium spp.) growing naturally as vineyard ground cover. Separating mealybug from GLRaV-3 grapevine host could be enhanced by a trap plant: an alternative host attractive to and retentive of the target pest. We evaluated the association between P. calceolariae and ‘Grasslands Huia’ white clover (GHWC). GHWC seed was sown under grapevines in a commercial vineyard (14 × 0.4 ha plots); the control was under-vine herbicide use (7 × 0.4 ha plots, where only few Trifolium spp. plants grew). After 2 years, GHWC cover peaked at 40

Populations of natural enemies in classical biological control programs often undergo recurring bottlenecks during importation and rearing, which can result in lower genetic variability and fitness. Enriching colonies with wild individuals, multiple importations or combining populations from different origins may help reduce this problem. Mastrus ridens (Hymenoptera: Ichneumonidae), a gregarious idiobiont ectoparasitoid of codling moth (Cydia pomonella) larvae was introduced to New Zealand from laboratory colonies dating to the 1990s. To improve populations for release, individuals from a most recent collection were imported from Chile (CL). Tests were conducted to measure genetic diversity of the parental populations (F0) and fitness traits of pure and mixed combinations of NZ and CL populations for F0 and the F1 generations. Results showed several effects depending on the population origin. CL females and males in the F0 generation lived longer than NZ females and males. Offspring from a CL mother lived longer than those from a NZ mother, and F0 and F1 females from a CL mother parasitized more larvae than females from a NZ mother. Genetic diversity estimates of F0 CL and NZ populations were 24% and 17% heterozygosity, respectively, and the NZ population had a larger proportion of diploid males than the CL population. Thus, no improvement in reproductive output resulted by mixing NZ and CL populations, as hypothesized, but a maternal effect was found in this species. This study shows the importance of understanding and tracking imported populations' genetic diversity and fitness traits in classical biological control programs.

Grapevine leafroll-associated virus 3 (GLRaV-3), an economically significant pathogen of grapevines, is transmitted by Pseudococcus calceolariae , a mealybug commonly found in New Zealand vineyards. To help inform alternative GLRaV-3 control strategies, this study evaluated the three-way interaction between the mealybug, its plant host and the virus. The retention and transmission of GLRaV-3 by P. calceolariae after access to non- Vitis host plants (and a non-GLRaV-3 host) White clover ( Trifolium repens L. cv. “Grasslands Huia white clover”), Crimson clover ( T. incarnatum ), and Nicotiana benthamiana (an alternative GLRaV-3 host) was investigated. For all experiments, P. calceolariae first instars with a 4 or 6 days acquisition access period on GLRaV-3-positive grapevine leaves were used. GLRaV-3 was detected in mealybugs up to 16 days on non- Vitis plant hosts but not after 20 days. GLRaV-3 was retained by second instars ( n = 8/45) and exuviae (molted skin, n = 6/6) following a 4 days acquisition period on infected grapevines leaves and an 11 days feeding on non- Vitis plant hosts. Furthermore, GLRaV-3 was transmitted to grapevine (40−60%) by P. calceolariae second instars after access to white clover for up to 11 days; 90% transmission to grapevine was achieved when no alternative host feeding was provided. The 16 days retention period is the longest observed in mealybug vectoring of GLRaV-3. The results suggest that an alternative strategy of using ground-cover plants as a disrupter of virus transmission may be effective if mealybugs settle and continue to feed on them for 20 or more days.

Despite numerous interceptions at the border, the brown marmorated stink bug (BMSB), Halyomorpha halys Stål (Hemiptera: Pentatomidae), is not yet established in New Zealand. Nevertheless, a classical biocontrol programme using the egg parasitoid Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae) has been initiated in anticipation of its likely arrival. The potential host range of the parasitoid in New Zealand was investigated by importing parasitised BMSB eggs into quarantine from Newark, DE, USA. Egg masses of seven species of Pentatomidae, including one sub-species, were individually exposed to naïve mated female T. japonicus in no-choice laboratory experiments. The results showed that predatory Cermatulus nasalis nasalis, C. nasalis hudsoni and Oechalia schellenbergii, and the phytophagous Monteithiella humeralis, Dictyotus caenosus, Glaucias amyoti, and Cuspicona simplex are all within the physiological host range of T. japonicus, although not all appeared to be equally susceptible to parasitism. No development or emergence of T. japonicus from eggs of the cosmopolitan pentatomid plant pest Nezara viridula were observed. The likely ecological consequences of releasing T. japonicus in New Zealand are discussed, as is the subsequent decision of New Zealand’s Environmental Protection Authority to approve release of the parasitoid once BMSB arrives in New Zealand.

The establishment of Mastrus ridens Horstmann (Hym: Ichneumonidae) in New Zealand, from introductions in 2012–2015, was assessed in 2016. Two assessment techniques were used: (1) 10-cm wide corrugated cardboard trunk bands deployed throughout the summer and winter periods to catch wild codling moth larvae and their parasitoids; and (2) sentinel, laboratory reared, codling moth larvae, cocooned within narrow, 2-cm wide corrugated cardboard bands, deployed on a monthly rotation throughout the spring and summer. Trunk band recoveries showed at least a low rate of establishment of Mastrus ridens across the country. Mastrus ridens females attacked sentinel hosts from early spring (prior to pupation of wild hosts) until late autumn. This evidence for multi-voltinism (compared with one or two generations of their host) signals a potentially effective parasitoid. Four other codling moth parasitoids were also recovered frequently from either wild or sentinel codling moth larvae, with differences between regions. The extent to which they may disrupt or enhance biocontrol by M. ridens remains to be investigated.

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.

The choice of groundcover plants used under grapevines may reduce the quantity of mealybugs found on grapevines in New Zealand vineyards. Preferences of Pseudococcus calceolariae and P. longispinus mealybugs on five clover cultivars were tested under ‘no-choice’ and ‘choice’ conditions. Two plants of each cultivar: ‘Karridale’(KS) (Trifolium subterraneum, L.), ‘Tripoli’ (TW), ‘Nomad’ (N) (T. repens), ‘Crimson cv’ (C) (T. incarnatum) and ‘Strawberry cv’ (S) (T. fragiferum) grown in pots, were arranged in randomised designs for the no-choice and choice tests and inoculated with newly emerged mealybugs. In the no-choice test, significantly more mealybugs (either species) were observed on KS and C than on TW, N, or S plants after 21 days. In the choice test, significantly more P. calceolariae were observed on KS than on TW, N, or S, while mealybug numbers on C were intermediate. Numbers of P. longispinus were significantly higher on KS and C than on TW, N or S. Mealybugs demonstrated preferences for KS and C over TW, N or S. These findings could aid development of recommendations for groundcover management in vineyards.