Family: - Psyllidae
Order: - Hemiptera
Paratrioza cockerelli (Šulc)
Trioza cockerelli (Šulc)
Summary:This psyllid is one of the most destructive pests of potatoes. It is an invasive exotic species that was found in WA in 2017 and on Norfolk Island in 2013. It is native to North America and was accidentally introduced to New Zealand in 2006 where it has become a serious pest of solanaceous crops including tomatoes and potatoes.
They look like tiny cicadas, because they hold their wings angled and roof-like over their body
Colour - When freshly moulted the body is initially pale green or light amber but soon darkens to mainly brown or almost black. The head and body have distinctive whitish markings which vary in size and intensity. Prominent white or yellow lines are found on the head and thorax, and dorsal whitish bands are located on the first and terminal abdominal segments. These white markings are characteristics of this psyllid, particularly the broad, transverse white band on the first abdominal segment and the inverted 'V'-shaped white mark on the last abdominal segment (Pletsch, 1947; Wallis, 1955), along with the raised white line around the circumference of the head.
Body - 1.3 - 1.9 mm in length (2.8 - 3.2 mm including the forewings).
Wings - They hold their wings angled and roof-like over their body. Two pairs of clear wings; the front wings bear conspicuous veins and are considerably larger than the hind wings.
Antennae - The antennae have a striped appearance due to the lighter colouration of the basal two-thirds of segments 3- 8. They are extend almost half the length of the body.
Legs - 6
Head - Prominent white or yellow lines. Raised white line around the circumference of the head
Thorax - Prominent white or yellow lines
Abdomen - Dorsal whitish bands are located on the first and terminal abdominal segments. Broad, transverse white band on the first abdominal segment and the inverted 'V'-shaped white mark on the last abdominal segment.
Habits - Fly when disturbed.
Colour - Orange, becoming yellowish-green and then green as they mature. Associated with whitish excrement particles.
Body - Elliptical, flattened, scale like. 0.23 to 1.60 mm wide depending on the instar. During the third instar, the wing pads are light in colour and evident and become more pronounced with each subsequent moult. A short fringe of wax filaments is present along the edges of the body.
Head - Compound eyes are reddish and quite prominent.
Habits - Sedentary but will move when disturbed.
Eggs - Small and on a stalk. 0.32-0.34 mm long, 0.13-0.15 mm wide. Mounted on a stalk of about 0.48-0.51 mm. Usually on the underside of the leaf near the edge.
Key Characters:Prominent white or yellow lines are found on the head and thorax, and dorsal whitish bands are located on the first and terminal abdominal segments.
Wings angled and roof-like over their body. Two pairs of clear wings with the front wings bear conspicuous veins.
2.8 - 3.2 mm including the forewings.
Biology:Adults are active.
Nymphs are mainly sedentary.
Good fliers and readily jump when disturbed.
The potato psyllid possesses a female-produced pheromone that attracts males (Guédot et al., 2010). Adult potato psyllids reach reproductive maturity within 48 hours post-eclosion, with females being mature on the day of eclosion and males at one day post-eclosion. Oviposition generally began two days after mating but was delayed when females mated within two days post-eclosion.
The optimum temperature is 27°C. Oviposition, hatching, and survival are reduced at 32°C and cease at 35°C (List, 1939; Pletsch, 1947; Wallis, 1955; Cranshaw, 2001; Abdullah, 2008; Yang and Liu, 2009; Yang et al., 2010a; Butler and Trumble, 2012). A single generation takes three to seven weeks, depending on temperature. Prolonged oviposition causes the generations to overlap (Pletsch, 1947; Wallis, 1955; Munyaneza et al., 2009a). Adults and nymphs are cold tolerant, with nymphs surviving temporary exposure to temperatures of -15°C and 50% of adults surviving exposure to -10°C for over 24 hours (Henne et al., 2010a).
Cool weather during migrations has been associated with outbreaks of this insect (Pletsch, 1947; Wallis, 1955; Capinera, 2001; Cranshaw, 2001).
Recent biology and ecology is in Munyaneza (2012), Munyaneza and Henne (2012) and Butler and Trumble (2012).
'Candidatus Carsonella ruddii', the obligate and primary endosymbiont of psyllids, has been confirmed in the potato psyllid (Nachappa et al., 2011; Hail et al., 2012). Beside Candidatus Liberibacter solanacearum, several other secondary endosymbionts associated with the potato psyllid have recently been reported, including the bacteria Wolbachia, Acinetobacter, Methyllibium, Rhizobium, Gordonia, Mycobacterium and Xanthomonas (Nachappa et al., 2011; Hail et al., 2012; Butler and Trumble, 2012; Arp et al., 2014). Currently, little information is available on the interactions and symbiotic relationship between these microorganisms and the potato psyllid.
Life Cycle:The pre-oviposition period is normally about 10 days, with oviposition lasting up to 50 days. Total adult longevity ranges from 20 to 60 days, and females usually live two to three times longer than males (Pletsch, 1947; Abernathy, 1991; Abdullah, 2008; Yang and Liu, 2009). Females lay 300 to 500 eggs over their lifetime (Knowlton and Janes, 1931; Pletsch, 1947; Abdullah, 2008; Yang and Liu, 2009).
The eggs are deposited singly, mainly on the lower surface of near the leaf edge. There may be numerous eggs on a single leaf. The eggs are initially light yellow and become dark yellow or orange with time. The eggs measure about 0.32-0.34 mm long by 0.13-0.15 mm wide, and are mounted on a stalk of about 0.48-0.51 mm. The eggs hatch 3-7 days after oviposition (Pletsch, 1947; Wallis, 1955; Capinera, 2001; Abdullah, 2008). The nymphs prefer sheltered and shaded locations and are usually found on the lower surfaces of leaves and move little during their development.
Nymphs and adults produce large quantities of whitish excrement particles, which may adhere to foliage and fruit.
Nymphs are elliptical from above and very flattened in profile and appear scale-like. They may be confused with the nymphs of whiteflies, although the TPP nymphs move when disturbed. There are five nymphal instars, with each instar possessing very similar morphological features apart from size. The size of the developing wing pads increases with each instar. Nymphal body widths are variable, ranging from 0.23 to 1.60 mm, depending on different instars (Rowe and Knowlton, 1935; Pletsch, 1947; Wallis, 1955). Initially, the nymphs are orange, but they become yellowish-green and then green as they mature. The compound eyes are reddish and prominent. During the third instar, the wing pads, light in colour, are evident and become more pronounced with each subsequent moult. A short fringe of wax filaments is present along the edges of the body. Total nymphal development time depends on temperature and host plant and has been reported to have a range of 12 to 24 days (Knowlton and Janes, 1931; Abdullah, 2008; Yang and Liu, 2009).
The psyllid is able to reproduce and develop all year round.
Habitats:Its principal habitats are cultivated or agricultural land and glass houses
Origin and History:It is native to North America and was found in New Zealand in 2006, Norfolk Island in 2012 and Western Australia in 2017.
Transport of host species or fruit is the most likely pathway for introduction to new countries or regions. Migration with the prevailing winds will then take over.
Distribution on potato tubers is unlikely.
Distribution:North America, USA, Central America, New Zealand, Oceania, Australia.
Significance:If introduced into a new area, the migratory behaviour of B. cockerelli, which favours quick and long distance dispersal, would put both the site of introduction and surrounding regions at risk.
The above-ground plant symptoms of infestation by B. cockerelli in potatoes and tomatoes include retarded growth, erectness of new foliage, chlorosis and purpling of new foliage with basal cupping of leaves, upward rolling of leaves, shortened and thickened terminal internodes causing clumped growth, enlarged nodes, axillary branches or aerial potato tubers, disruption of fruit set and production of numerous, small, and poor quality fruits (List, 1939; Pletsch, 1947; Daniels, 1954; Wallis, 1955; Munyaneza, 2012; Munyaneza and Henne, 2012).
The below-ground symptoms on potato include the setting of an excessive number of tiny misshapen potato tubers, production of chain tubers and early breaking of dormancy of tubers (List, 1939; Pletsch, 1947; Wallis, 1955). Other potato tuber symptoms include collapsed stolons, browning of vascular tissue concomitant with necrotic flecking of internal tissues and streaking of the medullary ray tissues, all of which can affect the entire tuber. Upon frying, these symptoms become more pronounced and chips or fries processed from affected tubers show very dark blotches, stripes, or streaks, rendering them commercially unacceptable and often called zebra chips (Munyaneza et al., 2007a,b; 2008; Secor et al., 2009; Crosslin et al., 2010; Miles et al., 2010; Munyaneza, 2012; Munyaneza and Henne, 2012).
When outbreaks occur 50% loss of yield has been reported in potatoes and total loss of marketable yield in tomatoes.
Potato psyllids acquire and spread the bacterial pathogen (Candidatus Liberibacter solanacearum) by feeding on infected plants (Munyaneza et al., 2007). The bacterium is also transmitted transovarially in the psyllid (Hansen et al., 2008), which contributes to the spread of the disease between geographic regions by dispersing psyllids.
The psyllid damages host plants and transmits the bacterial pathogen Candidatus Liberibacter solanacearum. This leads to reduced crop yield and premature decline and death of the infected plant. The bacteria is the causative agent of zebra chip disorder in potato tubers (Munyaneza et al. 2007; Abad et al. 2009; Sengoda et al. 2010). In tomatoes it causes leaf curling and yellowing as well as stunted growth in the fruit of tomatoes and capsicums (MAF Biosecurity 2008; Brown et al. 2010).
It is also a pest of other solanaceous crops such as pepper, eggplant, tobacco and tamarillo.
It also infests related plants such as nightshade (Solanum spp.), ground cherry (Physalis spp.), matrimony vine (Lycium spp.), field bindweed (Convolvulus arvensis) and sweet potato (Ipomoea batatas).
The psyllid infests plants in the Solanaceae and some species of Convolvulaceae and is thought to cause 'psyllid yellows' in tomatoes and potatoes, with yellowing of leaves and stunted growth (Brown et al. 2010; Sengoda et al. 2010). This may be associated with feeding by psyllid nymphs (List, 1925) and caused by a toxin associated with the insect (Carter, 1939), although the actual etiology of the disease is yet to be determined (Sengoda et al., 2010).
Legislation:It is a declared pest and under eradication in Australia.
B. cockerelli is on the list of quarantine pests in the EPPO region (EPPO, 2012).
Management and Control:Abamectin+ oil, spirotetramat, spiromesifen and bifenthrin provided high levels of control. Imidacloprid, spinetoram and mineral oil provided mediocre control (30-50% mortality). Azadirachtin, buprofezin+ oil and pyrethrin+ oil and provided some suppression only. The bifenthrin and abamectin had a rapid knockdown plus residual action which may be useful where rapid prevention of spread is important (Weir et al 2011).
Fast knockdown, repellent and anti-feeding insecticides are preferred to reduce the risk of the psyllids transferring the Liberibacter to the crop. This can occur from a single psyllid in 6 hours. Good insecticide coverage and/or translaminar activity is important because psyllids are commonly found on the underside of the leaves.
Kaolin and spray oils are occasionally used as anti-feeding agents where insecticides can't be used.
Biological Control:Chrysopid larvae, coccinellids, geocorids, anthocorids, mirids, nabids, syrphid larvae and the parasitoids Tamarixia triozae (Hymenoptera: Eulophidae) and Metaphycus psyllidis (Hymenoptera: Encyrtidae) have attacked TPP.
Some fungi provide some control (e.g. Beauveria bassiana, Metarhizium anisopliae and Isaria fumosorosae)
Related Species:Psyllids and Lerps.
Similar Species:Psyllid yellows and purple top diseases in potatoes have similar foliar symptoms.
References:CSIRO. The Insects of Australia. Melbourne University Press. (1991)
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