Pentatomoids as Vectors of Plant Pathogens 627
ground. The model predicted that chemical control would delay spread of the disease but would need to be
used continually to be effective. Another option was banding trees or otherwise blocking upward coloniza-
tion from the ground, but ultimately breeding programs may be the optimal solution (Sgrillo et al. 2005).
The genome of an isolate from South American coconut recently was sequenced and compared with
that of a latex-inhabiting species from Euphorbia. Interestingly, both strains have the requisite enzyme
to metabolize trehalose, presumably for nutrition in their insect vectors, but only the phloem-inhabiting
pathogen (i.e., the coconut hartrot isolate, Cocos nucifera) possesses multiple copies of an invertase
homolog, suggesting a greater ability to metabolize sugars (Porcel et al. 2014).
13.6.3 Oil Palms
“Marchitez” of oil palms, Elaeis guineensis Jacquin, first was reported in Colombia in 1963 shortly after
African oil palms were first cultivated there (Lopez et al. 1975; cited in Dollet 1984). The disease, also called
sudden wilt, is prevalent across northern South America, including Venezuela, Peru, Ecuador, Colombia,
Brazil, and Suriname. Trypanosomatids were recognized quickly as the etiological agent, and the connec-
tion between hartrot and marchitez was established when Phytomonas staheli was described from both
coconut and oil palms in Suriname (McGhee and McGhee 1979). On the basis of light and electron micro-
scopic analysis of flagellate morphology, McCoy and Martinez-Lopez (1982) showed both coconut and oil
palm pathogens in Colombia to be indistinguishable from P. staheli. Subsequent DNA analyses (Serrano et
al. 1999) supported the similarity of these pathogens, although multiple strains exist (i.e., between hartrot
and marchitez flagellates and even among hartrot isolates from different geographic areas). Hartrot strains
differed from those of marchitez by a single cytosine/thymine substitution in the region of DNA examined.
Using these methods, all of the palm isolate sequences could be distinguished easily from isolates of a dif-
ferent species from tomato fruit (Serrano et al. 1999). Transmission experiments in Brazil demonstrated
that Lincus lobuliger transferred from coconut infected with hartrot could pass the disease to healthy oil
palms (Resende et al. 1986). The progression of symptoms in marchitez also is similar to that of hartrot.
Leaves turn brown and then gray, beginning with the lower leaves and moving upward, fruit rots and drops,
and the root system is weakened (Dollet 1984 and references therein). Recently, a much slower progression
of marchitez disease has appeared in Peru, called slow wilt as opposed to sudden wilt. Initial leaf chlorosis
is evident, followed by dehydration and breakage of the leaves. The pattern of fruit decay, root rot, and leaf
discoloration differs from that of sudden wilt (Trelles Di Lucca et al. 2013).
Of the 35 species of Lincus, 13 species have been reported from economically important palms
(Maciel et al. 2015 and references therein). Confirmed vectors of marchitez (sudden wilt), in addition
to L. lobuliger in Brazil, include L. lethifer Dolling (Ecuador) and L. tumidifrons Rolston (Colombia)
(Desmier de Chenon 1984, Dolling 1984, Perthuis et al. 1985, Alvarez 1993). In a study of possible vec-
tors of slow wilt, a high proportion of L. spurcus Rolston was found to carry trypanosomes in the abdo-
men and head, but actual transmission could not be verified, possibly because of the long incubation time
of the disease (Trelles Di Lucca et al. 2013). Surprisingly little is known of the biology of Lincus spp.,
which are difficult to observe, occupying crevices between the bases of fronds and other hidden loca-
tions (Camargo and Wallace 1994). Desmier de Chenon (1984) described the biology of L. lethifer on oil
palms in Ecuador. Diseased trees harbored hundreds of bugs in the crown between sheaths of the flower
stalks and under the root bulb; apparently healthy trees supported bug colonies as well, but, within a few
months, all of the these trees also had developed symptoms of marchitez. As with adults and juveniles,
eggs were found in protected areas between sheaths or in cracks in the root. Bugs were most active and
visible in the evening, as was observed for L. lobuliger in Brazil
All stages of Lincus tumidifrons were collected from the bases of fronds on oil palms in Colombia
(Alvarez 1993) and reared in the laboratory to obtain life history data. Successful rearing required dark
conditions; no adults were obtained from cages exposed to white light. Rearing techniques using con-
tinuous darkness also have been developed for the hartrot vector L. bipunctatus along with a method of
inoculating the bugs’ digestive tract with Phytomonas cultured in vitro (Dollet et al. 2002, as L. croupius).
Ground insecticidal sprays controlled the disease in oil palm plantations, presumably because the
bugs moved among plants by walking rather than flying (Desmier de Chenon 1984); a similar effect was
observed in coconut plantations when a ring of endrin was applied around the trees (Louise et al. 1986).