P. W. Shaw

Abundance of leafrollers and their parasitoids on selected host plants in New Zealand

Abstract The comparative abundance of orchard pest leafroller larvae was determined on eight host plants in the vicinity of pipfruit orchards. The greatest numbers occurred in Canterbury, followed by Nelson, Hawkes Bay, and Central Otago. In Hawkes Bay, leafroller larvae were Ctenopseustis obliquana (41%), Planotortrix octo (15%), Epiphyas postvittana (16%), and Cnephasia jactatana (9%), and were most abundant on poplar, willow, and alder. In Nelson, leafrollers were E. postvittana (25%), Planotortrix excessana (23%), C. obliquana (23%), and C. herana (22%), found on willow, alder, clover, poplar, gorse, broom, dock, and plantain. In Canterbury, larvae were C. herana (51%), E. postvittana (34%), and P. octo (15%), mainly on broom, gorse, alder, poplar, dock, and clover. Leafrollers were very rare on host plants sampled in Central Otago, despite their pest status in horticulture. A total of 1460 larvae were reared to adults from the four regions, with 31% parasitism, of which two thirds were Dolichogenid...

Resistance management of lightbrown apple moth, Epiphyas postvittana (Lepidoptera: Tortricidae) by mating disruption.

Abstract Epiphyas postvittana (Walker) resistant to azinphos-methyl caused 1.7 and 5.4% fruit damage in 1983/84 and 1985/86 in apple orchards at Moutere Bluffs, New Zealand. Surveys from 1984 to 1989 of resistance in orchards and scrub nearby showed 3.5% survival of the diagnostic dose (LD99.95) in January and 7.6% survival in April. Survive did not increase between years. Catches in pheromone traps inside affected orchards indicated high levels of male activity despite regular application of chlorpyrifos. Mating disruption, along with the application of chlorpyrifos, was investigated as a possible solution to the continued inability to achieve economically acceptable leafroller control with insecticides alone. Two ha of apple trees were treated with Shin Etsu Chemical Co. dispensers (1000/ha) containing (E)-11-tetradecenyl acetate and (E,E)-9, 11-tetradecadien-1-yl acetate (56.5 and 2.8 mg per dispenser), in January 1987. No males were caught for over 11 months after the pheromone application. Harvest da...

Trapping Dasinuera mali (Diptera: Cecidomyiidae) in Apples

Abstract The midgeDasineura mali (Kieffer) (Diptera: Cecidomyiidae) is a significant pest of apples (Malus spp.), and the recent identification of the female sex pheromone is enabling new direct control tactics to be considered. Direct control using male suppression will require knowledge of the frequency of multiple mating, dispersal and colonization rates, and the efficiency of male removal. Males were able to mate up to five times, with a mean of 2.7 times when presented in a 10 female-to-1 male group, designed to simulate male suppression. Male catch in response to the pheromone loading was curvilinear over 4 orders of magnitude from 3 μg to 30 mg on rubber septa. Trapping using a high-dose pheromone lure was combined with oil-based traps similar to the inexpensive New Zealand “Lynfield trap” used for tephritid surveillance, to test male suppression in young orchard blocks at 500 traps per ha. Monitoring traps indicated 96% lower catch in the treated plots compared with control plots, over 137 d. However, a lack of shoot tip infestation in both treated and untreated plots indicated limited colonization and prevented an assessment of potential population suppression. Furthermore, a contribution to these results from communication disruption cannot be ruled out. Replicated transects of frequency of infested shoots from a mature orchard across the adjacent young block confirmed that colonization by ovipositing females was essentially limited to the first 30 m.

Factors affecting feeding site preferences of lightbrown apple moth, Epiphyas postvittana (Lepidoptera: Tortricidae), on apple trees in New Zealand.

Abstract The infestation of apple (Malus domestica) trees by Epiphyas postvittana (Walker) larvae was studied over 3 years. Fresh damage to leaves increased progressively during the season, although in Nelson it declined in April. Fruit damage was first detected in December and increased throughout the season. The incidence of fruit damage was most strongly correlated with the surface area of fruit. Single leaves were the preferred feeding site for larvae on terminal shoots, although when whole branches were examined, most shelters occurred between two leaves. Feeding sites on fruit predominantly involved contact with a leaf or another apple. A field experiment examined the influence of physical contact and fruit maturation on leafroller damage. E. postvittana larvae were offered a choice of feeding sites involving leaves and three types of “apple” namely untreated apples, apples treated with chlorethephon to promote ripening, and plastic balls. There was 16% more damage on treated compared with untreated fruit, but similar levels of damage to leaves touching the three types of apple. Although riper fruit were more attractive to E. postvittana larvae, their preference for physical contact had a greater influence on the selection of feeding sites. The increase in fruit damage over time was mainly due to the increasing extent of contact between leaves and other fruit as the apples enlarged.

Geographic changes in leafroller species composition in Nelson orchards

Abstract Pheromone traps placed along a transect across the Nelson district from Waimea to Riwaka were used to determine the distribution of three native and one introduced species of leafroller of importance to fruit growing in the Nelson district. The light brown apple moth, Epiphyas postvittana (Walker), was dominant throughout the district. The brownheaded leafrollers, Ctenopseustis obliquana (Walker) and C. herana (Felder & Rogenhofer), and the greenheaded leafroller, Planotortrix excessana (Walker), were each recorded in various proportions at all trap sites. Ctenopseustis obliquana was dominant from Moutere Bluffs to Riwaka, while C. herana was dominant nearer to Nelson.

Susceptibility of seedling Pyrus clones to pear sawfly (Caliroa cerasi) (Hymenoptera: Tenthredinidae) damage

Abstract Pear slugs, the larvae of the sawfly Caliroa cerasi, can cause extensive damage to pear leaves in organic or reduced‐spray orchards. Breeding for resistance provides a strategy for the long‐term control of this pest. Twenty‐two accessions from the Horticulture and Food Research Institute of New Zealand pear breeding programme were selected to cover a range of field‐assessed susceptibility to this pest. These were grafted onto Pyrus calleryana seedling rootstock, and the young plants were arranged in a blocked trial design in a ventilated glasshouse. The plants were covered with insect‐proof netting, into which adult sawfly were released. The number of eggs per plant did not differ among the susceptibility classes, but the level of damage was related to the predicted level of susceptibility. This study confirmed the existence of variation in the resistance of pear genotypes to pear slug damage.

Evaluation of the synthetic sex pheromone of the obscure mealybug, Pseudococcus viburni, as an attractant to conspecific males, and to females of the parasitoid Acerophagus maculipennis

The obscure mealybug, Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), is a cosmopolitan pest. In New Zealand, recently introduced management tools include the host‐specific parasitoid Acerophagus maculipennis (Mercet) (Hymenoptera: Encyrtidae) established in 2001, and pheromone‐baited monitoring traps available since 2005. Red delta traps baited with rubber septum lures impregnated with 4.0 μg of the mealybug synthetic sex pheromone, placed in apple orchards in Hawkes Bay and Nelson, trapped both male P. viburni and female A. maculipennis. Two generations of both species per year were discernible, but numbers were low in spring and parasitoids were not trapped during winter (June to September). Male P. viburni catches reached a plateau at a pheromone dose of ca. 1.0 μg per lure but numbers of A. maculipennis per trap increased up to 100 μg per lure, the maximum dose tested. A mathematical model showed that the lures had a half‐life of about 7.4 days and were most attractive to P. viburni with a dose of 0.19 μg, and that the trap effectiveness decreased rapidly once the release rate dropped below the optimum. The model also predicted that the initial pheromone dose should be increased from 0.19 to 5.41 μg per lure as the desired period of deployment increased from 0 to 9 weeks. A dose of 4.0 μg had an initial relative effectiveness of about 55%, reached peak effectiveness after about 5 weeks, and fell to 55% relative effectiveness again after about 8.3 weeks. We conclude that an initial pheromone load of 4.0 μg is appropriate for practical monitoring of P. viburni during the New Zealand summer. Future applications of the sex pheromone for managing the pest and parasitoid are discussed.

Pear sawfly (Caliroa cerasi) (Hymenoptera: Tenthredinidae) host preference and larval development on six Pyrus genotypes

Abstract The larvae of the sawfly Caliroa cerasi can cause serious damage to pear (Pyrus sp.) foliage particularly in organic or reduced‐spray orchards. Six pear cultivars and selections, three with low susceptibility to pear slug damage and three with high susceptibility, were subjected to oviposition choice tests in the field and subsequent larval development rates were monitored to clarify the nature of the variable susceptibility. Observed differences in oviposition rates corresponded with the low and high susceptibility categories of the genotypes. Larval development rates differed among genotypes and were inversely related to density of hatched eggs (a surrogate measure of leaf damage). These results confirm that host oviposition preference is a key factor influencing susceptibility to pear slug. It is further argued that feeding‐induced plant resistance and larval migration could be important factors influencing pear sawfly populations on pear trees.

Releases of Hemisarcoptes coccophagus Meyer (Acari: Hemisarcoptidae), a predator of armoured scale insects, in the South Island

Hemisarcoptes coccophagus Meyer were released into apple, pear and plum trees infested with Quadraspidiotus perniciosus (Comstock), Q. ostreaeformis (Curtis) and/or Lepidosaphes ulmi (L.) in Nelson, Mid-Canterbury and Central Otago between 1991 and 1996. They were recovered from only one property in Nelson (on Q. perniciosus on pear) up to 12 months after the initial release, but not 6 years later. H. coccophagus developed successfully on Q. perniciosus in the laboratory. Possible reasons for the apparent failure of the mite to establish are discussed.

Recent records of mealybugs and their parasitoids in Nelson pipfruit orchards

ABSTRACT The majority (65%–94%) of mealybugs collected from harvested apples in Nelson, New Zealand, orchards between 2008 and 2011 were Pseudococcus longispinus. The remainder (35%–6%) were P. calceolariae, although a few P. viburni were occasionally found. Traps baited with newly developed synthetic pheromone of P. calceolariae were deployed in orchards in 2011 and attracted females of the mealybug parasitoid Alamella mira. The mealybug parasitoid complex in Nelson apple orchards was assessed over an 8-week period in autumn during 2012 and 2013 by deploying sentinel mealybugs on sprouting potatoes. Potatoes were infested with P. longispinus (in 2012 and 2013) and P. calceolariae (2012 only). They were deployed in orchards to capture parasitoids that were active during the trapping period. The sentinel mealybug-infested potatoes were placed in delta traps in the orchards for about 2 weeks and then retrieved and held in a laboratory in Auckland for 4–6 weeks. Parasitoid mummies were collected and emerging adults identified to species. In 2012, four species (Tetracnemoidea peregrina, T. brevicornis, Coccophagus gurneyi and Ophelosia charlesi) were recovered from three orchards near Motueka. In 2013, three species (T. peregrina, C. gurneyi and Gyranusoidea advena) were recovered. Monitoring methods appeared to influence the complex of parasitoids recovered. A combination of monitoring methods, including possible kairomonal responses of mealybug parasitoids to host pheromones and rearing parasitoids from fruit and foliage naturally infested with mealybugs, may provide the best assessment of mealybug parasitoid diversity and abundance in orchards.