CARIBBEAN FOOD CROPS SOCIETY

THIRTEENTH ANNUAL MEETING ST. AUGUSTINE TRINIDAD, W. I. JULY 6-12,1975

PUBLISHED WITH THE COOPERATION OF THE UNIVERSITY OF PUERTO RICO MAYAGUEZ CAMPUS 1980

VOLUME XIII CURRENT STATUS OF MAJOR INSECT PESTS ON SOME FOOD CROPS IN THE COMMONWEALTH CARIBBEAN

K.U. BUCKMIRE Entomologist, Caribbean Agricultural Research and Development Institute, University Campus, St. Augustine, Trinidad.

ABSTRACT

The production of cabbage, carrot, onion, pigeon pea and sweet potato in Barbados, St. Vincent and Trinidad and Tobago is reviewed. Major insect pests, their control and distribution are recognised with re- gard to the CARIFTA/CARICOM region and inter-regional trade.

Problems associated with these pests are discussed covering sus- ceptibility of the plants and pests, resistance of the pests to insecticides and assessment of economic damage.

Suggestions are made for multidisciplinary research in pest con- trol by plant breeders, other biological scientists, physical scientists, engineers, nutritionists and economists to follow the entire plant cycle including harvest and post-harvest stages.

INTRODUCTION

Over the last 10 years the problems of food shortage, and mal- nutrition together with foreign exchange difficulties in the Caribbean have stimulated the awareness for higher productivity levels in the agri- cultural sector. However, increasing the production of economic and locally consumed crops accelerate the use of pesticides and proliferate the ravages of insect pests.

In the Commonwealth Caribbean cabbage and pigeon pea are widely grown and used for local consumption. Carrots, sweet potato and onion are export crops from St. Vincent and Barbados respectively. Data on production show that in Trinidad and Barbados there are increasing numbers of large farms while in St. Vincent the crops are grown exclusively by small farmers.

Trinidad and Tobago in 1973 imported 3.3 million pounds of carrots of which only 9.5% valued ait TT $103,642 came from within the CARICOM area. Barbados produced some 1.8 million pounds of onions in 1973 and exported to the value of BDS $1.7 million. For the same year Trinidad and Tobago imported from non-CARICOM source

116 7.7 million pounds of onion valued at some IT $1.7 million. St. Vincent in 1974 exported 3.3 million pounds of sweet potato and netted E.C. $564,379.

It follows that the stimulus is there for increasing agricultural production but, it is a fact of environmental dynamics that as intensifi- cation of food production proceeds the problems of insect pests increase.

Table 1 gives the production of a few crops in Barbados, St. Vincent and Trinidad and Tobago.

TABLE 1. Total Production and Trade in Selected Crops, 1973.

Obs) IMPORT (Trinidad and Tobago) Crop Production Non CARICOM CARICOM

Cabbage 1/ 15,248,000 252,454 -

Carrot 2/ 519,325 3,050,051 318,810

Onion 3/ 1,800,000 7,707,000 - Sweet potato 18,723,841 2,650 2,741,088

1/ - Barbados and Trinidad and Tobago 2/ - St. Vincent (export) 31 - Barbados

The production of 13.5 million pounds of cabbage during 1973 in Trinidad and Tobago was about 80% of the potential yield. Suah et al., in Jamaica obtained a 90% yield after using the same chemicals as that of Parasram.

In order to produce cabbages in the Caribbean insect pest con- trol is becoming most important. Plutella xylostella is showing resistance to carbamates and most organophosphates. Even though some farmers have gone back to lead arsenate the damage continues. Bennett reports that in Barbados the parasite Apanteles plutellae is becoming more active.

117 MAJOR INSECT PESTS, THEIR CONTROL AND DISTRIBUTION

Cabbage

Throughout the Caribbean cabbage is attacked by numerous in- sect pests. The more important ones are: the cabbage budworm, cabbage looper, cabbage white butterfly, diamond back moth, fall armyworm and leafminers. They all damage the leaves but can be catergorised by the method of feeding.

Foliage Feeders

Caterpillars of the cabbage looper, Trichophisia ni (hubner); Cabbage white butterfly, Ascia monuste L. ; Diamond back moth, Phi- tella xylostella L.; Fall armyworm, Spodoptem frugiperda (J.E. Smith) feed on the wrapping leaves and the head of the cabbage plant. Bennett discusses many natural enemies of the above pests in the Caribbean. From surveys mounted only the egg parasite Trichogramma sp. and the larval wasps Apanteles spp. appear to give any measure of control.

With intensive cabbage production in the 3 islands biological agents do not offer economical control of the pests and as such chemi- cals are widely used. Dipterex sp. 95 at 0.14% A.l. and Diazinon E.C. 60 applied as 0.075% A.l. generally control all the caterpillars. PluteUa is the exception. When the cabbage looper is the predominant pest application of lannate W.P. 95 at 0.05% A.l. adequately suppresses the population. The cabbage white butterfly caterpillar can be effectively controlled by spraying with a Bacillus thuringiensis pesticide at the rate of 0.65 kg per hectare.

Borer

The caterpillar of HeUula phidileaUs (wlk.), the cabbage bud- worm, at first attacks the leaves then bore into the leaf base or the stem apex. When the stem is damaged apical dominance is obstructed result- ing in the lack of head formation. In Trinidad Parasram records good control using 0.09% A.l. Gardona E.C. 24.

Scaring leaf feeders

Maggots of two or three Liriomyza spp. cause yellowing and browning of foliage leaves. The attack is chiefly on the seedlings where the photosynthetic efficiency of the plants is greatly affected. Spraying with Diazinon E.C. 60 at 0.075% A.l. gives good control.

118 Carrot

The web worm, Hymenia fasciata and an armyworm Spodoptem sp. infest the leaves of carrots causing severe damage. Application of Dipteres sp. 95 at 0.25% A.l. and Gardona E.C. 24 at the rate of 0.05% A.l. gives economic control.

Onion

Though 5 species of insect pests are of major economic impor- tance, in Barbados where most of the onions are grown Spodoptera sunia (Gn.), armyworm, and Thrips tabaci (Lind.), onion thrips, cause the bulk of the damage. Caterpillars of the armyworm eat the leaves cutting down the plant. Thrips rasp and suck the leaves causing blotching, dis- tortion and necrosis with the plant eventually withering. Application of Diazinon E.C. 60 at 0.13% A.l. controls the thrips population'. Sevin sprayable powder 85% at the rate of 0.14% A.l. and Dipterex sp. 95 at 0.16% A.l. reduce the population of armyworm below economics da- mage.

Pigeon pea

Pigeon pea pod borers, Ancylostomia stercorea (Zell.).· Helio- this virescens (Fab.) and Fundelh pellucens (Zell.) cause most of the eco- nomic damage in the Commonwealth Caribbean. Parasram shows that Ancylostomia is the most serious pest at flowering time. Acanthosceli- des zeteki (Kingsolver) CaUosobruchus chinensis (L.) and Callosobruchus maculatus (F.) are common on the drying pods in the field and result in enormous damage during storage. Spraying at peak flowering time with Dipterex sp. 95 at 0.14% A.l. and Gardona E.C. 24 0.1% A.l. reduce in- festation to below 4.5%. In storage Gardona w.p. 75 appears to control the bruchids.

Sweet potato

Many insects infest sweet potato. The caterpillar of the leaf- webber, PUocrocis tripunctata (Fab.) and the adult bettle Euscepes postfasciatus (Fair.) fed on the leaves. Larvae of the scarabee weevil and the sweet potato weevil, Cylas formicarius elegantulus Summers, infest the tubers causing considerable economic damage. Megastes gran- dalis (Gn.) deposit eggs at the base or axil of leaves and the larvae tunnel through the stem and tubers.

A 0.1% A.l. Sevin sprayable powder controls the leaf feeders. Birlane E.C. 24 at the rate of 0.11% A.l. controls Cylas, Euscepes and

119 Megastes. Dipping of insect-free slips in dieldrin or birlane solution helps in delaying insect attack.

There is an uneven distribution of some of the major insect pests. Table 2. shows that Cylas formicarius elegantulus (Summ.) have so far been recorded in Antigua, Guyana and St. Kitts. Only Barbados, Guyana and Jamaica report Cylas formicarius as being of pest impor- tance. Fundella peüucens (Zell.) is a predominant pigeon pea pod borer in Barbados but is fairly common in St. Lucia.

Fennah reports that the leaf webber on sweet potato is common in Greater and Lesser Antilles but in recent times only St. Vincent re- cords it as of pest importance.

Megastes grandalis (Guen.) is a major pest of sweet potato in Trinidad but is yet to be found in any of the other CARICOM territories.

STATUS AND ASSESSMENT OF ECONOMIC DAMAGE

Damage to the five crops may cause loss of weight, of quality and of yield. The loss of weight due to an individual insect is very small in most cases but, with increase populations the amount is significant.

With a view to assess the destructiveness of the tobacco bud- worm, H. virescens, on pigeon pea 50 newly emerged larvae were reared individually on green pigeon pea seeds in the laboratory. Table 3 shows that each caterpillar cats an average of 16.4 seeds during its feeding stage and can cause a weight loss of 1.96 grams.

Recent work at the University suggests that a fertile female is capable of producing a mean of 1111.7 eggs in her life time. Since the percentage mortality from egg to larvae is approximately 30.5%, one adult is capable of infesting a field with 772.6 larvae. In the laboratory under Trinidad conditions the average length of a generation from egg to adult is about 30 days. Theoretically it is possible to have twelve generations in a year. The dry season, January to May appears to in- fluence a degree of diapause. Losses as a result of insect infestation of dried pigeon pea is very scant for the Caribbean but in Nigeria, Caswell estimates that 50 to 60% of cowpea seeds are damaged by CaUosobru- chus maculatus F. As this insect does most of the damage in these is- lands it can be estimated that 30 to 50% of pigeon pea seeds are damaged in storage.

120 TABLE 2. Major inject pests and their distribution on cabbage, carrot, onion, pigeon pea and sweet potato in the field

CROPS COUNTRIES INSECT PESTS Cabbage Carrot Onion Pigeon pea Sweet Potato A Β D G Go ) Κ L Τ V

Ancylostomia stercorea (Zell.) Aphlds Ascia monuete Cylas formicarius Cylas formicarius eiegantulus / (Summers) Empoasca fabae (Harris) y / Euscepes posfasdatus (Fairmaire) S Fundeüa pellucens (Zell.) • Heliothis virescens (Fab.) Htllula phidikalis (Wik.) / Jferae cinguIata(F.) Hymenia fatciata Liriomyza sp. Lbiomyza pusilla (Meigen/) Mesgastes grandalis (G uen.) fllocrpcis tripurctata (Fab.) • Plutelia xylosteila L. • + + Spodoptera sp. y ++ + Spodoptera frugiperda / (J.E. Smith) • / Spodoptera sunia (Gii.) • Thrips tabaci (Lind.) • Trichoplusla ni (Hubner) Abbreviations Code:

A - Antigua D · Dominica Gu Guyana Β - Barbados G - Grenada J Jamaica

Κ - St. Kitte - Montserrat - St. Vincent L - St. Lucia Trinidad & 1 crop •• « 2 crops Tobago TABLE 3. H. viretcent damage to pigeon pea wed In the Uborttory

Experiment Seed Damaged (Number») Eatlmated low in weight (gm»)

1 91 10.92 2 69 8.28 3 72 8.64 4 142 17.04 5 115 13.80 6 73 8.76 7 100 12.00 8 125 15.00

Total 787 94.44

Total Larvae 48

DISCUSSION

Insect pests in the region need to be carefully and constantly monitored to prevent the introduction of less widely distributed pests. With increasing trade and travel between the CARICOM area it is even more important to have in each island strict quarantine measures.

Generally the production of agricultural crops both for the lo- cal market and export within the region is increasing. This stimulates increased acreage under production thus creating large areas of single crops making the incidence of insect pests more relevant; as a conse- quence of which there is a demand for more pesticides. Reports from the Americas, Asia and the Caribbean indicate insect resistance to many of the chemical insecticides on the market.

Soil types and microclimatic conditions may be significant in the population dynamics of a particular insect pest but, the cost-benefit analysis input would be a desirable feature in trying to justify the need for putting the limited resources into a particular crop production pro- gramme. The plant should be researched in its entire environmental niche, looking at the dormant and growth phases as well as the harvest and post harvest periods. Perhaps the post-harvest problems in carrot, pigeon pea and sweet potato may be a significant factor in the economics of the crops.

122 REFERENCES

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