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Box Psyllids-Biology, Occurrence and Predators

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Box Psyllids-Biology, Occurrence and Predators Box psyllids the most important insect pests of box plants in southern England and South Wales - their biology, occurrence, and associated predators. Summary by Hasbullah 2 Damage done to box plants Psylla buxi and Spanioneura fonscolumbii are the major pests of Muhammad1, Both the psyllid species damage box plants by P. box plants in southern England and South Wales. Peter McEwen1 and sucking the sap of the terminal shoots and at the buxi is a widespread species found in all box William Symondson2 same time produce unsightly white waxy secretions plantations surveyed, whereas S. fonscolumbii on the plant. It is the feeding by P. buxi nymphs P. appears to be more patchily distributed. buxi 1Insect Investigations Ltd which causes the characteristic cupping of the nymphs are usually confined inside the cupped School of Biosciences terminal leaves. P. buxi nymphs stay within the leaves of the plant whereas in S. fonscolumbii cupped leaves and undergo moulting to subsequent Cardiff University nymphs are exposed on the shoots. Both species nymphal stages. Usually the 5th nymphal stage will produce unsightly white secretions on plants. PO Box 915 leave this shelter and develop into an adult outside Cardiff CFIO 3TL Adults of both species usually appear from April to the cup. In the case of S. foncolumbil, although no 2School of Biosciences July. Only a few leaf cupping is produced, the shoot becomes species of predators are associated with box psyllids Cardiff University dehydrated. The white secretions produced are and their numbers are always low. The main insect PO Box 915 principally used to protect the psyllids from predators observed are anthocorid bugs, ladybird Cardiff CF10 3TL dehydration and also appear to attract ants, which beetles, earwigs, and green lacewings. A tendency feed on the honeydew produced by feeding psyllids. for psyllids to preferentially infest variegated as The ants protect the psyllids from predators. The opposed to non-variegated plants was noted. white secretions produced by S. fonscolumbii are more obvious than those of P. buxi as most of the 1 Biology secretions are directly on the shoot. Both the Psyllids or jumping plant lice are the major insect cupping of the shoots and the white secretions pests of box plants in southern England and South cause substantial cosmetic damage to the plants. Wales. The two species of psyllids which cause Under extreme cases the whole plant is covered most damage to box plants are Psylla buxi and with the white secretion which can coat the ground Spanioneura fonscolumbii (Homoptera: Psyllidae) beneath the plants. (McEwen et al., 1997). P. buxi is a widespread species found in all four box plantations surveyed, whereas S. fonscolumbii was confined to two plantations. The adults of both species are small, about 3 mm 3 Field incidence long, and superficially resemble miniature cicadas. Both psyllid species lay their tiny orange spindle- The two species are easily distinguishable by the shaped eggs under the leaf bud scale, somewhere presence of three black dots on the top cells of the between late summer and autumn. The eggs enter wing in S. fonscolumbii when observed under the diapause to survive the winter and emerge into the dissecting light microscope. In the case of P. buxi no first nymphal stage during February or March. such marking is found and it is also relatively larger Adults usually emerge around the month of April and darker green in colour than S. fonscolumbii. to July. We also believe that a few psyllids overwinter as adults (see below). In southern Differentiation between the two species at the England and South Wales adults of both species are larval stages is extremely difficult as both species found in abundance in June and July. Monitoring of emerge at more or less the same time of the year adult field populations using sticky yellow traps and look alike. However, P. buxi larvae are initially was carried out monthly in southern England from confined to the inside of cupped leaves whereas S. 1997 to 1999 based on the methodology of Horton fonscolumbii nymphs are exposed and distributed on et al. (1995). The use of sticky yellow traps to the surface of the shoots, so differentiation is monitor the psyllid population was made following possible in this way. In addition, under the a six month trial which showed that yellow traps dissecting microscope, P. buxi larvae appear to be accounted for 46.8 % of all psyllids caught as darker with a v-shaped circumanal pore which compared to 15.2% red, 14.3% blue, 0.7% green surrounds the anus as compared to lighter colour and 10.1% white. This pattern was true for both and t-shaped circumanal pore in S. fonscolumbii. species as reported by McEwen and Baker (1997). Figure 1 shows that the peak of the adult psyllid population appeared between May and July in all 3 the summer months earwigs were sometimes References years studied. The worst outbreak occurred in 1997 found on the shoots where the psyllids were most Horton, D R; Butts, E C; where up to 500 S. fonscolumbii were caught per active. Generally speaking ladybird numbers were Lewis, T M & Coop, month from a total of 4 square feet of yellow sticky very low and less than 13 were collected from any L B (1995) Sticky trap trap. Although P buxi sometimes dominated in the specific area per year. The so-called common green catch of winterform sticky trap catches in this experiment, it is lacewing was the least common predator found in and summerform pear interesting to note that S. fonscolumbii almost southern England, and was also infrequent in South psylla (Homoptera, always outnumbered P. buxi in direct plant beating Wales. Only on a few occasions were larvae of Psyllidae) over non- studies (Fig. 2). In this method, at each sampling, 6 lacewings collected through plant beatings. orchard habitats. Pan plants were randomly selected from the box However, a relatively high population of adults was Pacific Entomologist plantation. Each plant was beaten 3 times by hand observed hibernating in the roof of a building 7(3), 176-189. over a sticky tray and the insects collected were adjacent to one of the experimental areas in McEwen, P K; Baker, taken to the laboratory for identification. southern England. Generally speaking the M; Muhammad, H & population numbers of all these predators was low Symondson, W 0 C The discrepancies between these two methods and almost insignificant compared to the psyllid (1997) Psyllids of sampling may relate to differences in flight population. Manipulations of these natural (Psylloidea: behaviour between the species, seemingly implying predators such as inundative release or construction Homoptera) attacking a greater tendency for P. buxi to disperse. From of artificial refugia, could be an important part of Box (Buxus field observation the direct plant beating method the biological control of psyllids. sempervirens) in South is a more accurate determinant of real psyllid England. Antenna 21(4) numbers and is an important tool which can be 200-201 used to monitor psyllid build up prior to any control measures. 5 Do psyllids prefer non-variegated to McEwen, P K & Baker, variegated box varieties? M (1997) Pest control Using the plant beating method we can also It is generally believed that psyllids prefer non- in boxwood. Topiaries, detect, at an early stage, the presence of psyllid variegated box to variegated box varieties (Nguyen, Autumn Vol 5 larvae based on the white secretions which fall on 1968). This belief is based on the anecdotal Nguyen, T H (1968) the beating tray, particularly from S. fonscolumbii. observation that no serious infestation is observed Role de la temperature Interestingly we also detected a few overwintering on the variegated varieties even during major dans revolution et adult psyllids. Overwintering S. fonscolumbii adults psyllid outbreaks. However, this might be due to relimination de la usually appeared with a banded abdomen especially the fact that white secretions do not show up so diapause larvaire de in the females. In the case of overwintering P. buxi well on variegated plants. We decided to see if this Psylla buxi (Horn., adults no such banding was observed, but they did observation was really true. A surveillance study Psyllidae). Ann. Soc. appear to be relatively bigger than usual and more was carried out on both variegated and non- Ent. Fr. (N.S.) 4, 69-74. brownish in colour. variegated varieties using the plant beating method between February 1998 and November 1999. Six Acknowledgement plants from each box variety were sampled every This work is sponsored 4 Insect predators associated month and the number of psyllids caught was with box psyllids by Langley Boxwood recorded. From this study it was found that 84.1% Nursery, Rake, Liss, Direct plant beating and sticky traps were used to of all psyllids caught were from variegated as Hampshire GU33 7JL, sample predators. From this it appears that only a compared to 15.9% on non-variegated variety and U.K and particular few species of insect predators are associated with this difference was statistically significant (P < thanks are extended to box plants. These predators usually appear during 0.01). Both psyllid species were preferentially the proprietors, spring having undergone diapause to overwinter. attracted to variegated plants where 84.8% and Elizabeth and Mark Most of the predators emerge from diapause just as 78.0% of S. fonscolumbii and P. buxi respectively Braimbridge psyllid nymphs become active. The major insect were recorded. These results indicate that the predators collected in order of importance based anecdotal evidence that psyllids preferably attack on their abundance are anthocorid hugs (Anthocoris non-variegated box is incorrect and the reverse Fig.3 Predators collected nemorum), ladybird beetles (Propylea 14 - punctata, seems to be true.
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