Bruchus pisorum
They may not be actual weevils , but there is no question that these pests are furtive . Hiding inside the pea plant seeds within the pods , they can ruin an otherwise beautiful , freehanded crop .
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The worst part : they ’ll make themselves known after all the severe work of growing and harvesting is done , often emerging from the seeds in store .
Infested seed
What can be done about them ?
Everything you need to bonk about these little insects is laid out for you below !
Here ’s what we ’ll cover :
What You’ll Learn
What Are Pea Weevils?
pea plant weevils are not truthful weevils , and they in fact belong to the leaf beetle family , Chrysomelidae . They lack the schnoz that distinguishestrue weevils . Other usual names for these pesterer include pea seed mallet , or pea overhang .
love as significant pest since the mid-1700s , they were accidentally preface to North America from Europe in the 1600s via infested seed .
Now they are found everywhere that peas are cultivated , including all over the United States and southern Canada , and in most moderate regions of Asia , Europe , north Africa , and Australia .
They are monophagous , feeding only onPisum sativumor field of operations peas , attacking plant life both in garden and in large commercial-grade discipline .
Identification
Bruchus pisorumadults are five to seven millimeters long , and two and a half millimeter wide . The females are slightly bigger than the males .
With a globular shape , the beetles have long stage and a short head . Their antennae are less than a third of the length of their organic structure .
diffused Robert Gray or brown to black in color , they have irregular ashen flecks over their elytra , or flank covers . The elytron are short , with the last abdominal section reveal . This segment sports a white design that is account by some as being plane - shaped .
The larva are legless , creamy white , atomic number 6 - shaped chuck with a brown point . They rise up to five millimeters long .
B. pisorumeggs are bright yellowish , ellipse - work , and one and a one-half millimetre long .
Though their vulgar names are very similar , these are not the same species as pea folio weevil ( Sitona lineatus ) , which feed on the crucifix nodules underground as well as the leaves and growing tips of annual leguminous plant including field peas , lentils , andfava beans .
The grownup of this specie are slender and grayish - brown , with three distinct , abstemious - coloured longitudinal chevron run down the pectus .
Biology and Life Cycle
B. pisorumproduce one generation per year , taking 50 to 80 days to dispatch the cycle from oviposition to adult emergence .
adult overwinter beside fields and emerge once temperatures gain 68 ° F , often co-occur with the time when peas begin to blossom . They will travel up to five kilometers to find the flowers , attracted by their odour .
grownup will invade the craw for three to four weeks . Both male and females feed on flowers , leaves , or cod , but initially they are specially drawn to pollen .
Females ’ ovary senesce after consuming significant amount of pollen , and mating will occur after this . Volatile phytochemical released by the plant life remind the scratch of egg - laying .
female lay their egg on the outside of fuel pod . The eggs incubate in one to three weeks , depending on the condition , and the larvae burrow into the pod , leaving distinctive , midget , dot - like entrances .
Larvae maturate in the developing seeds inside the pods , or inside stored or germinating seeds , going through four larval stages ( instar ) over the course of four to eight weeks .
Feeding on the peas from within , only one larva can survive per acquire seed . Optimal temperature for larvae and pupae development kitchen range from 89 to 105 ° F .
After pupate for about two week inside the seeds , the adults that emerge chew an obvious , two - and - a - half - mm rotund passing muddle .
This can happen before harvest , allowing the adult to disperse to overwintering sites , or about a month post - harvest , surprising the granger or nurseryman . Large populations can decimate a stored craw . sham ejaculate is not fit for human consumption .
The liveliness cycle ca n’t uphold in computer storage , however , as the adult need pollen to reproduce , and developing seedcase for the larva to tunnel into .
Monitoring
Since the adults often do n’t emerge from the seed , and harm is n’t obvious until the peas are in storage , many retrieve ofB. pisorumas a storage pest . However , as is obvious from their biology and spirit cycle , the trouble starts much earlier .
Farmers often apply sweep nets to supervise for adults every three to four days once flowering begins . If you have a low crop , check over the flowers for adults , as these pests are very attract to their perfume .
Organic Control Methods
Luckily , home gardeners rarely see these pests in phone number that ca n’t be check with natural methods , specially ethnical controls .
Cultural Control
ethnical command is very effective for these pests , making up for the lack of biologic controls and special chemical pick .
Sown seed needs to be costless of louse , and garden hygiene is essential . Be sure to purchase seeded player from a reputable purveyor .
Field sanitation practice – such as destroying harvest rest , prevent pod shattering at harvest by picking pea before they are dry , and get rid of volunteer pea plant industrial plant – can go a long way toward protecting succeeding crops .
If you leave topographic point available for the adult to overwinter , such as in debris bequeath on the sharpness of the subject or garden , reckon on facing repetition infestations year after class .
Crop rotation is effective if unspoilt sanitation is also apply , especially in small gardens . Trap croppingis still being studied and an effective trap crop is yet to be found .
former planting and harvest run well . former planting gives the plant life a luck to blossom before the pesterer overrun .
other crop , when the insects are still immature and terms is minimal , along with harvesting before adults issue and move to hibernation areas , can decrease pest abundance the following year .
Storing harvested pea at 1 ° F overnight can killB. pisorumin any leg of their life bicycle that may be hide inside , and chilling should n’t affect sprouting rate in saved seed . This is a neat thought if you plan to constitute your own cum .
Biological Control
Triaspis thoracicusis a flyspeck wasp that parasitizesB. pisorumlarvae and it is used in Australia and Canada for biocontrol .
Using sheep to graze out crop residual is more practical for many farmers and smallholder . The animals will use up shatter pods , Tennessean pea plant plants , and any other infested plant parts .
Organic Pesticides
unluckily , there are no organic pesticides available today that are effectual against these gadfly .
fortuitously , the other method acting describe above provide respectable control if multiple strategy are combine .
Chemical Pesticide Control
Pesticides are generally unneeded for utilisation in home gardens .
Once the larva have dream up and burrowed into the pods , they are protected from most insecticides , so timing is keyif you are using spray . Aim to spray for the adult after most have invade but before the eggs are laid .
Commercial growers will often hold off until just after the first flowers shrivel up to spray .
Border atomizer are also effective , take in the overwintering adults correctly before they head into the field .
Malathion , carbaryl , pyrethroids , and organophosphates may be utile against this cuss . However , keep in mind that many pesticides are elusive onbeneficial insectsand pollinators .
The Weevil That Isn’t
It can be intimidating to get laid your peas might be harbour a out of sight pest at this very mo .
The secure news is cultural controls are very efficient , so start early and expend a variety of methods to hit this beetle where – and when – it consider .
And for more data aboutgrowing peasin your garden , check out these guides next :
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Sylvia Dekker
