Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Entomological Research.

Abstract

Records are given of the attack on teak [Tectona grandis] by Xyleutes ceramicus, Wlk., in the experimental plot in Burma in 1937 and 1938; as the trees are now becoming too large to permit thorough investigation and the work is therefore being discontinued, the results obtained since 1930 [cf. R.A.E., A 25 454; 26 338] are summarised and discussed. The incidence of the Cossid was much greater in 1930-33 than in the later years, when it was of only moderate intensity. In the years since 1933, about 25 per cent. of the attacks have been recorded in September or later and are, therefore, considered to represent transfers of the larvae from other trees. The numbers of living larvae in the trees were greatest in July-August of each year and later rapidly decreased. In each generation, an average of 11 per cent. of the original larval population survived into the second year, 3.3 per cent. having given rise to adults after one year and the remainder having died. In 1931 and 1937, 33 and 23 per cent. of these survivors gave rise to adults, but no larvae of the 1935, 1936 and 1938 generations lived through the second year. The greatest numbers of larvae died in August and September each year, but the percentage mortality was greatest in April-June in three years and in November in two. Between 1932 and 1939, 56 moths emerged in the acre plot, 68 per cent. after one year in the larval stage and the remainder after two years. Males were more numerous than females. It was found that attacks did not necessarily originate from moths emerging in the plot itself. The average incidence of attack was directly proportional to the girth of the trees and was slightly greater in those growing on a slope with a north-east aspect than on one facing the south-west [cf. 25 454]. The dominant trees in a stand are more liable to infestation than suppressed ones. An experiment begun in 1937 in which larvae were placed on trees in a cage at Zibingyi showed that the percentage mortality of established larvae was 83, even when all natural enemies were excluded. The incubation period at Zibingyi varied from 15 days in March at an average maximum temperature of 93.9°F. to 12 days in April at one of 101.8°F.
Data from 17 localities showed that the percentage parasitism of X. ceramicus by Nemeritis tectonae, Perkins, decreases as the trees grow older. For trees up to 7-8 years old, the percentage parasitism varied from 20 to 80 and sometimes reached 100 during the first 2-3 years of the attack, but by the time the trees were 20 years old this percentage was never as high as 20 and often 10 or less. The observations showed that B. tectonae parasitises larvae in the small wood of saplings and in the crowns of older trees in preference to those in the main trunk, and though the site of borer attack moves up the tree as it gets older [cf. 25 301], that of attack by Nemeritis is considerably higher than the majority of the larvae. In a search for an alternate host of Nemeritis [cf. 25 75], a young larva of a species of Indarbela, probably I. quadrinotata, Wlk., was found under the bark in the fork of a 3-year-old teak shoot on 1st March 1939, and a male of N. tectonae emerged from it on 4th April. Cossids of the genus Indarbela are widely distributed throughout Burma and are numerous in localities in which Nemeritis has not been recorded from X. ceramicus. Larvae and a living pupa of X. ceramicus were found in the stems of Clerodendron infortunatum, from which this Cossid has not previously been reported.
No serious outbreaks of Hyblaeapuera, Cram., or Hapalia machaeralis[Eutectona machaeralis], Wlk., which defoliate teak, occurred during the year, probably owing to abnormally high rainfall throughout Burma during May. Parasitism of larvae and pupae of Hyblaea bred in the insectary reached 9 per cent., of which 50 per cent. was caused by Apanteles spp. and 35 per cent, by Tachinids. Other parasites of Hyblaea studied were Brachymeria euploeae, Westw., and the Ichneumonid, Echthromorpha notulatoria, F. The latter was shown to have an egg capacity of about 160, and 64 progeny were obtained from 387 host larvae presented to one female. B. euploeae readily parasitized the pupae, but did not attack larvae in any instar. Of nearly 1, 500 eggs of Hapalia collected in the field, 5.6 per cent, were parasitized; 89 per cent. of the parasites were Telenomus usipetes, Nixon, and the remainder Trichogramma sp. [stated in a recent paper (28 538) to have been identified as Trichogrammatoidea nana, Zehnt.]. A list is given of the parasites found attacking the larvae in the field; Apanteles machaeralis, Wlkn., accounted for 20 per cent, of the total parasitism (6.5 per cent.) and unidentified Tachinids for 41 per cent. The most important parasites of the pupae, 9.5 per cent, of which were parasitized, were Tetrastichus sp., B. euploeae and Xanthopimpla cera, Cam. Breeding of the introduced parasite, Cedria paradoxa, Wlkn. [28 537] was continued throughout the year, and 103, 000 individuals were liberated in 10 regeneration centres in Lower Burma; although the host population was low, recoveries were made in three localities in May and November 1938 and in February 1939. It is doubtful whether this Braconid survives the hot weather, as maximum temperatures of 90°F. and over apparently inhibit reproduction. No further breeding is to be carried out, as it is considered that the parasite has been released in sufficient numbers to become established if it is able to do so. Small numbers of the Ichneumonid, Angitia (Diodes) gardneri, Cushm., and the Bethylid, Goniozus montanus, Kieff., obtained from Madras [cf. 28 538] were liberated for the control of Hyblaea, and unsuccessful attempts were made to breed both parasites in the insectary. No recoveries of either were made during the year. In addition to Apanteles spp. and Tachinids, which parasitize Hyblaea [cf. 28 537], parasites shipped to India comprised Tetrastichus sp. and Bracon (Cremnops) desertor, L., which are parasites of Hapalia. It was subsequently reported that both Tetrastichus sp. and B. desertor were already present in India.
Most of the other defoliators of teak are sporadic, but occasionally cause fairly severe defoliation and delay the recovery of the trees from attacks by Hapalia and Hyblaea. The most important of those bred during the year were Boarmia (Ascotis) selenaria, Schiff. (imparata, Wlk.), B. (Serraca) infixaria, Wlk., Hyposidra talaca, Wlk., Macalla plicatalis, Hmps., Astycus lateralis, F., on young plants, two species of Apogonia, and Orthoptera.
Investigations in December on Pachydissus birmanicus, Gardner, which bores in Xylia dolabriformis[Xylia xylocarpa], showed that 12 trees with an average girth at breast height of 4 ft. 4 ins. contained a total of 316 galleries of this Cerambycid; one tree contained no galleries and another 75. The galleries contained 3 large living larvae that must have been in the trees for more than a year and 37 less than 0.5 in. long that must have hatched from eggs laid in October. Records showed that most of the adults emerge in October, though one emerged in January and a few in April. A living beetle was found in the pupal chamber of a gallery opened in December. The mature gallery, which is large, takes 2 or 3 years to occlude and is frequently the site of incipient rot and termite injury. The Cerambycid can mature in wood only 9 ins. in girth, and galleries were found in the small branches of the crowns. Over 80 open galleries were counted in one tree that had been killed by Pachydissus; in this case the sapwood must have been entirely consumed. The leading shoot of one of the trees examined had been killed in the same way. The Cerambycid has few natural enemies; no parasites were found, and only 3 of the 316 galleries examined had been investigated by woodpeckers, though these were numerous. It is probably distributed throughout Burma, but economic damage was reported from only 4 divisions, and control measures are considered to be unnecessary. The only other important borers of X. dolabriformis are Zeuzera coffeae, Nietn. [27 693] and species of Indarbela; the latter injure trees in the pole stage but are largely confined to the crowns of older trees. Detailed investigations on the status and life-history of Indarbela showed that the majority of the adults emerge in March, but that small larvae were present in February; it is considered that these would probably give rise to adults in October-November. The pupal stage lasted about 20 days. Species of Indarbela have been recorded from 10 food-plants, of which X. dolabriformis appeared to be preferred. A list is given of the leaf-eating insects recorded from X. dolabriformis during the year; the most important were Maruca testulalis[Maruca vitrata], Geyer, Striglina scitaria, Wlk., and Achaea Janata, L., but no serious damage was caused.
Logs of Swintonia floribunda were attacked by the Scolytids, Xyleborus fallax, Eichh., and X. submarginatus, Bldf., and the weevils, Zeugenia histrionica, Pasc., and Trochorrhophalus dipterocarpi, Mshl. ; the percentage of wood rendered useless by infestation averaged about 5 and rose to 50 in some logs, but speedier transport to the mill largely eliminated damage by insects later in the year. Logs of Anogeissus acuminata were attacked at the depot by the Bostrychid, Heterobostrychus aequalis, Waterh., and the Lyctid, Minthea rugicollis, Wlk., and in the forest after felling by the Cerambycid, Stromatium longicorne, Newm., and the Lamiid, Olenecamptus indianus, Thorns. To determine the relative resistance of barked and unbarked logs of Pentacme suavis to attack by borers, two adjacent trees were felled in May and the bark was removed from one of them. This tree remained virtually unattacked, but the other became heavily infested by species of Sphaerotrypes, Xyleborus and Diapus and to some extent by the Cerambycid, Dialeges pauper, Pasc., and the Brenthid, Amphicordus improportionalis, Hllr.
Sarcocephalus cordatus was severely defoliated in one forest area by the Pyralid, Margaronla (Glyphodes) punctiferalis, Wlk., in June, and Dipterocarpus tuberculatus by the Lymantriid, Dasychira cerigoides, Wlk., which was first observed in September, had completely defoliated trees over large areas in several reserves by November and continued to cause severe injury until the end of May 1939, apparently completing its life-cycle in about 75 days. Cassia trees were severely defoliated by the Pierids, Catopsilia crocale, Cram., and Terias blanda silhetana, Wallace. Observations on the life-history of Xyleutes persona, Le Guillou, which bores in living Cassia, were continued [cf. 27 693]. In Rangoon, 89 moths emerged from the 75 trees under observation; emergence occurred in every month except June, but was most abundant in February, March and September. In Maymyo, 5 moths emerged from 53 trees in April-May and 2 in October; a heavy population of larvae of various sizes in one tree was killed by injecting a concentrated solution of paradichlorobenzene in kerosene into the galleries. Tung trees (Aleurites fordi and A. montana) are sometimes defoliated in the Shan States by Achaea Janata [cf. 27 693] and Dasychira mendosa[Olene mendosa], Hb., and seedlings up to 2 years old may be severely damaged by the leaf-feeding adult of A stycus lateralis. A large root-feeding Prionid killed several seed bearers of A. fordi and also attacked A. montana.