5 color photos, 2 illustrations, 3 tablesThe pepper weevil is a severe pest of sweet and hot peppers. The grubs feed inside buds of fruit, and there may be five to eight generations of pepper weevil in a year. This publication contains complete information on pepper weevil biology, sampling and control

Riley, David

Sparks Jr., Alton N.

Texas A&amp;M Repository

The pepper weevil, Anthonomus eugenii Cano(Figure 1), is a severe insect pest of sweet andhot varieties of pepper, Capsicum spp., in thesouthern United States, Mexico, CentralAmerica, Hawaii and several Caribbean islands.Adult pepper weevils feed on fruit and leaf budsand lay eggs on flowers, buds and fruit. Larvae(grubs) feed inside pepper pods. This causes pre-mature fruit drop and can result in significantcrop losses of up to 50 percent (Figure 2). Often,entire pepper fields must be plowed underbecause too few fruit are left to harvest, and theinfestation poses a threat to later pepper plant-ings. Up to 90 percent fruit loss has been mea-sured in experimental plots infested early in theseason and left untreated. Additionally, evenmoderate infestations late in the season cancause complete loss of fields. Larger fruit do notimmediately drop when they become infested,and entire fields are often abandoned because ofconcern in shipping infested fruit to markets.L-5069The Pepper Weevil and Its ManagementDavid G. Riley and Alton N. Sparks, Jr.*Texas AgriLife Extension Service • Zerle L. Carpenter, Director • The Texas A&M University System • College Station, TexasFigure 1. Pepper weevil adult on bell pepper.Figure 2. Pepper weevilgrubs in pepper fruitand fallen bud.*Assistant Professor, Texas Agricultural Experiment Station,and Associate Professor and Extension Entomologist, TexasAgricultural Extension Service.Pepper Weevil BiologyThe pepper weevil shares many of the charac-teristics of other members of the genusAnthonomus. The weevil feeds on relatively fewplant species, and females oviposit (lay eggs) onflower buds or fruit.  Pepper weevil grubs devel-op inside the bud or fruit, and like the cotton bollweevil, Anthonomus grandis, the pepper weevilhas three larval instars and multiple generationsper year. Diapause has not been detected in thepepper weevil, which means that its northernrange is limited to areas that can support pepperweevil host plants throughout the winter.Management should begin with an under-standing of the pepper weevil’s life cycle (Figure3) and the factors that influence its populationgrowth. Information on the biology of the pepperweevil is summarized in Table 1. Generationtime and the number of generations per year aredetermined primarily by host availability andtemperature. The pepper weevil can complete itslarval development in the fruit and/or flowers ofmost pepper varieties and on several species ofnightshade. Investigators report varying genera-tion times for the pepper weevil, with the largestdifferences occurring between summer and fallwhen temperatures vary most. In hot weather thegeneration time is shortest, about 13 days.Newly emerged adults are light brown anddarken to a grayish-black in 2 to 3 days. Themating and egg laying begins about 2 to 3 daysafter emergence. In one season it is possible tohave three or four generations of weevils, and ifFigure 3. Life cycle of the pepper weevil. Illustration by E. Vasquez.the spring and fall crops overlap, problems withpepper weevil can be much greater in the secondcrop.  In South Texas, survival of adults betweencropping seasons is greater between the fall andspring crops because of lower temperatures.The size of the fruit, previous pepper weeviloviposition or feeding, and the availability ofsufficient host plants are important factors in theselection of egg-laying sites. The plant speciesthat sustain higher weevil populations are typi-cally the more preferred. Developing fruit 1.3 to5.0 centimeters in diameter are preferred oversmaller or larger fruit for egg laying. Pepperweevil females probably lay most of their eggsduring the day, and avoid fruit buds with eggsalready present. Varietal differences in peppersmay affect host preference somewhat, but are notsufficient to be utilized in control programs.More research is needed to determine theeffects of varietal differences. Recent tests sug-gest that pepper varieties which produce largenumbers of small fruit (unlike bell pepper, forexample) have more fruit that escape damage.Sampling for Pepper WeevilsWeevils are likely to re-infest fields as theymove to and from secondary host plants and cullsites. Little data regarding pepper weevil move-ment is available, but they may be able to movelong distances. Most field observations suggestthat pepper weevils disperse slowly through pep-per fields early in the season, which can result inlocalized clumps of weevils and their damage.Peppers planted next to infested nightshade, pep-pers or pepper culls are likely to be attackedfirst.  The clumped pattern of pepper weevil infesta-tion in the field makes scouting more difficult.There is a great tendency to underestimate pep-per weevil numbers unless sufficient samples aretaken. More pepper weevils are found alongfield margins than in the interior of the field, sosampling along the margins will give a betteridea of infestation and reduce scouting time.Pepper weevil adults are often found in the samesample locations from week to week. It is impor-tant to locate these “hot spots” of pepper weevilactivity to determine if they need extra chemicalcontrols and to discover possible causes of wee-vil re-occurrence that might be avoided in thefuture. Methods of detecting pepper weevil activityinclude 1) inspecting terminal buds or bud clus-ters for pepper weevil adults, 2) using yellowsticky traps for adults, 3) making direct weevilcounts using whole plant inspections, 4) scoutingfor feeding damage or egg laying in terminal budclusters, and 5) using boll weevil traps baitedwith pepper weevil males or pheromone extracts.The presence of medium-size fallen fruit shouldnot be used as the first indication of pepper wee-vil activity, because at this point it is far too lateto prevent significant yield loss (Figure 4). Foreach day that a mature adult goes uncontrolled,six new weevils are produced. Thus, if a fruittakes 3 days to abort and another 2 days passbefore the problem is detected, each adult femalewould have laid an additional 30 eggs prior todetection of the fallen fruit. Also, weevils insideTable 1. The biology of the pepper weevil,Anthonomus eugenii Cano.Generation time 2 weeks in hot weather 3 weeks in mild weather6 weeks in cold weatherGenerations/year 5 to 8Longevity of adults 3 months average with food 1 to 3 weeks without foodOviposition period more than 1 month averageFecundity average 340 eggs/adultOviposition rate average six eggs/day Natural enemies PredatorsSolenopsis geminata (fire ant)Strunella magna (meadow lark)Tetramorium guineese (ant)Parasitic waspsPyometes venticosisCatolaccus incertusPediculoides ventricosusBracon mellitorHabrocytus pierceiZatropis incertusCatolaccus hunteriNatural controls freezing temperaturesoverheating of fallen fruitdestruction of fallen fruitlack of host materialHost plants peppers and nightshadesfallen fruit cannot be controlled with insecti-cides. Only the adults that come in contact withthe insecticide are controlled with sprays, so it isimportant to determine adult activity in the field. The lack of frequent scouting and accuratemonitoring of pepper weevil populations aremajor limitations to the implementation of actionthresholds (using scouting data to decide whetheror not to spray). Where pepper weevils areknown to be a problem, fields should be sprayedperiodically from before first bloom to harvest.This is the recommended practice if a reliablesampling method is not used, but this practiceuses excessive insecticides if weevils are not pre-sent and can lead to other pest problems. Studiesof the relationship between damage and weevilinfestation levels suggest that the following lev-els can be used to prevent economic loss in bellpeppers: 1) 5 percent damaged terminals or 2)one pepper weevil per 200 plants, inspecting twoterminal buds per plant. With the terminal budinspection method, at least 800 plants (approxi-mately one-half hour of scouting) must beinspected without finding a single weevil beforea decision not to treat a pepper field can be madewith a high level of confidence (Table 2). If wee-vils are found in less time, then insecticide appli-cations are justified. Table 2.  Sampling for pepper weevil adultsor damage in bell pepper.Sampling Minimum samplemethod (time)* CommentsWhole plant 25 plants (1 hour) Approximatelyinspection 2 minutes per plant, less time on seedlings.Terminal bud 1,600 terminals 1 second perinspection (1/2 hour) terminal; searchfor adults only.Damage to 200 terminals 10 seconds perterminal buds (1/2 hour) terminal; must inspect closely for egg laying.*Only if no weevils at all are found within these mini-mum times should a decision be made not to treat.Control of the Pepper WeevilTo economically control weevils once theybecome established, it is best to implement aspray program based on frequent, accurate scout-ing. Plants should be checked in many locationswithin the field to properly assess the level ofpepper weevil activity. Insecticides registered forpepper weevil are listed in Table 3. These organ-ic insecticides do not cause excessive residueson harvested fruit. The availability and relativelylow cost of effective insecticides make regularapplications an attractive option for reducingrisk. Even so, an intensive scouting program andthe use of action thresholds for weevils and otherpepper pests should be used to reduce the possi-bility of insecticide resistance; avoid outbreaksof secondary pests such as mites, whiteflies andthrips; reduce insecticide costs; better target lim-ited-use insecticides; and monitor efficacy ofcontrol practices. The two recommended thresh-olds for pepper weevil, as stated earlier, are 5percent damaged terminal clusters or one adultTable 3.  Insecticides registered for the pepper weevil on bell pepper.Pre-harvestLbs AI/acre interval CommentsPermethrin 0.1-0.2 3 days No more than 1.6 lbs AI/acre/season.Oxamyl 0.5-1.0 7 days Best in calendar sprays or in combinations1.Esfenvalerate 0.025-0.05 7 days No more than 0.35 lb AI/acre/season, suppression.Cryolite 25-50 0 if washed Wash off residues or apply before fruit formation.1Other products used in combination: azinphos-methyl, methomyl.Figure 4. Fallen fruit in an infested pepper field.per 200 plants with two terminal buds inspectedper plant. In the Lower Rio Grande Valley theselevels are best used after an early-season preven-tive spray at first bloom.Immature weevil stages cannot be controlledwith insecticides, even systemics. However, asmany as 30 percent of the weevil grubs in fallenfruit may be killed as sunscald heats and driesthe fruit.Recommended cultural controls include thedestruction of pepper residue immediately afterthe last harvest, removal of pepper culls whichcan harbor weevils inside, making sure trans-plants aren’t infested, and the removal of night-shade from pepper fields and field margins. Ifnew peppers are planted next to old peppers thenthe old peppers should be sprayed before plow-ing because destruction of the old host materialcan trigger a migration of weevils to the newpepper planting. Because host plant availabilitylargely determines weevil population level, themost effective control methods, other than pesti-cides, are eliminating pepper culls and secondaryhost plants such as nightshade. The only biologi-cal control known at this time is the feeding ofcertain hymenopterous parasites on pepper wee-vil grubs; however, their impact appears to beminimal. Parasites have been found in oxamyl-treated plots where an action threshold for insec-ticide application was used, so parasitism cancomplement insecticide controls.Figure 5.  Timing and placement of sprays areimportant for pepper weevil control. Illustration byA. Riley.Recommended Management Practicesfor Pepper Weevil1. Avoid locations with pepper weevil infesta-tions when selecting sites for a new peppercrop. 2. Scout fields weekly beginning at transplant-ing or before first bloom. Also scout night-shade plants and old pepper residue in thearea before planting to determine if a pre-plant cleanup is needed.3. Avoid carry-over of weevils from one sea-son to the next. This is a problem wherepeppers are cut back to produce a secondcrop or crop residue is left standing afterharvest.4. If weevils infest early, begin controls atfirst bloom to prevent an early build-up ofpepper weevil.5. Target insecticide sprays at the adults bygetting good spray coverage and timingapplications with the presence of adults ortheir emergence from fallen fruit.Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disabili -ty, religion, age or national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, asamended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, TexasAgricultural Extension Service, The Texas A&M University System.7.5M–9-95, Revision HORT 6

The Pepper Weevil and Its Management

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The Pepper Weevil and Its Management

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The Pepper Weevil and Its Management

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