threatened by stink bugs and fungi

As marginal cropping and low-input farming develop, sunflowers are gaining recognition as an appropriate crop to domesticate rotationally with maize.

Producers in dryland producing areas discover sunflowers interesting attributable to their common drought tolerance and capability to offer comparatively fixed harvests below adversarial climate circumstances and promising revenue attributable to sunflower oil’s utility in meals preparation, biofuel manufacturing, and cosmetics and skincare merchandise.

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Sunflower flour and cake are fed to animals and the seeds are used for fowl seed and human consumption. Nonetheless, sunflower manufacturing is challenged by varied insect pests.

The sporadic prevalence of the false chinch bug (Nysius natalensis) and the illness sclerotinia head and/or stalk rot, attributable to the fungus Sclerotinia sclerotiorum, performs a job within the decline of sunflower plantings.

In South Africa, the area between 24°S and 30°S is the first rising area for sunflowers.

As much as 80% of the nation’s sunflower manufacturing happens in areas which have a semi-arid surroundings with variable and rare rainfall, low humidity and intense summertime solar radiation.

Within the jap highveld districts of Mpumalanga and the jap parts of the Free State, the crop is usually sown between November and December.

Within the western areas of the Free State and North West, planting dates is perhaps prolonged till mid-January; within the northern portion of the manufacturing space, planting takes place in January and February.

The northern area’s late planting date is set by the world’s late rainfall.
Sunflower planting is regularly delayed previous the customary dates by delayed spring rains all through the entire summer season rainfall space.

4 species of Nysius are present in South Africa: Nysius binotatus, N. pallidus, N. stali and N. natalensis, also referred to as the false chinch bug.

This pest is widespread in South Africa’s sunflower-producing areas.

Beneficial environmental circumstances, comparable to fewer days of frost and a later onset of frost, permit for larger availability of appropriate host crops and an extended interval for the event of populations.

False chinch bug females lay their eggs on, near, or between the bract leaves and the seeds.

Eggs could be deposited individually or in teams. Newly hatched nymphs are small and difficult to see with the bare eye.

They undergo 5 nymphal instars (the stage of the insect between successive moults) earlier than rising as adults.

An grownup false chinch bug is recognized when wings have developed on the physique, are 4mm to 5mm lengthy and have a greyish-brown look.

The polyphagous behaviour of N. natalensis, together with a perfect temperature vary for development inside its zone of distribution, performs a major position in dictating the pest’s inhabitants density.

Weedy host crops play a essential position in sustaining false chinch bug populations.

They like weedy host crops, however when weeds are absent they depend on different host crops comparable to wheat (Triticum aestivum), onions (Allium cepa), leeks (Allium ampeloprasum), garlic (Allium sativum), alfalfa (Medicago sativa), pistachio nuts (Pistacia vera) and extra generally, sunflowers.

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Pigweed (Amaranthus hybridus), tall fleabane (Conyza albida), white goosefoot (Chenopodium album) and customary purselane (Portulaca oleracea) are often ample in patches of various sizes inside sunflower manufacturing areas that represent a number of species.

All of those weedy hosts’ seeds in addition to sunflower seeds are appropriate for N. natalensis’s meals provide, improvement and survival. False chinch bugs persistently have websites to oviposit owing to the number of hosts and the succession of host plant varieties all through the season.

Sudden invasion of crops

The prevalence of false chinch bugs is unpredictable and sporadic.

This species’s unpredictable means emigrate over giant distances whereas utilizing atmospheric disturbances as a way of transportation might account for the sudden and sudden invasion of sunflower crops in areas the place weedy host crops are scarce.

Based mostly on observations, sunflower crops are sometimes harmed by false chinch bug from March, when headlands or close by weedy crop fields, that are hosts to the species, are cultivated.

At seed-fill, they transition from weeds throughout autumn senescence to late-planted sunflower.

Throughout the seedling stage and budding interval, giant numbers of false chinch bug might invade and feed on the vascular tissues of the younger sunflower crops, inflicting them to wilt and perish.

A discipline might include giant numbers of this pest purchase solely a small variety of crops expertise extreme to irreversible harm that lowers seed yield, oil content material, and poor germination.

handle the pest?

Since sunflower seeds are additionally appropriate for the feeding, improvement and survival of false chinch bug, administration needs to be targeted on sustaining the pest on its wild hosts.

Resulting from this pest’s polyphagy, or robust urge for food, and skill to breed efficiently on widespread weed species — which permits it to determine inside sunflower farms — cultural management strategies may be capable to scale back pest populations and crop harm.

Headlands and close by fields needs to be stored weed-free from the beginning of the season to forestall the build-up of pest populations and decrease the chance of short-range unfold.

Furthermore, in the course of the seed-fill stage of sunflower crops, weedy headlands and close by fields with host crops ought to not be hoed as a result of doing so destroys the host crops, which ends up in an invasion of the sunflower fields.

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When planting, attempt to keep away from executing it too late. Farmers ought to pay shut consideration to the time at which weeds are managed, as a result of when the popular host plant, weeds, is eradicated in the course of the administration of sunflower fields, it forces the false chinch bugs to maneuver to sunflower heads.

Weed management is important to successfully management populations of false chinch bugs, nevertheless the time of execution is essential.

Delaying weed eradication in rows, surrounding fields and neighbouring fields till after sunflowers have surpassed their most weak phases (seedling and budding interval) will assist restrict the motion of false chinch bugs from their most well-liked host crops to sunflowers.

Sclerotinia head and stalk rot

Sclerotinia sclerotiorum is a harmful fungal pathogen that has an intensive host vary, which probably exceeds over 500 plant species.

These embody crops comparable to soya bean (Glycine max), beans (Phaseolus vulgaris), canola (Brassica napus), lupines (Lupinus perennis), a wide range of vegetable crops in addition to many weed species, which can all function alternate hosts for the pathogen. On sunflowers, it additionally leads to sclerotinia head and/or stalk rot.

As a result of solely particular person crops in a discipline might develop into contaminated, sclerotinia stalk rot of sunflower is just not a direct substantial hazard to sunflower manufacturing in South Africa.

Sclerotinia head rot, nevertheless, can lead to vital hurt, particularly to crops which can be sown early and ripen in cool, moist circumstances.

Along with the principle producing areas for sunflowers (Limpopo, North West, Mpumalanga and Free State), different provinces that develop sunflower might also expertise sclerotinia head rot.

It’s regarding as a result of the illness affecting sunflowers continues to unfold towards the western areas that produce maize.

The 2 most vital rotation crops (sunflower and soya bean) on this maize-producing area might now not be economically viable to sow attributable to elevated inoculum ranges.

This means that it’s tough or almost inconceivable to eradicate the illness after it has unfold all through a area or discipline.

It is among the important causes of sunflowers’ decline as a maize different in some areas, like Mpumalanga.

Though seasonal variation is typical, it can’t be believed {that a} location with a historical past of sclerotinia head rot is disease-free if the illness doesn’t seem there throughout a specific season.

Since S. sclerotiorum sclerotia have been identified to outlive as much as seven years within the soil, there could also be an inoculum ready for the best circumstances to permit for an infection. If beneficial circumstances maintain, the illness can resurface within the subsequent season.

How does Sclerotinia infect sunflower crops?

Within the discipline, the fungus exists as sclerotia within the particles of crops. Within the soil, sclerotia can stay for as much as seven years. An infection occurs when there are vital quantities of rainfall and low temperature in the course of the flowering interval.

When sclerotia germinate in moist soil, they produce apothecia, that are tiny fruiting buildings that resemble mushrooms. In moist climate, apothecia develop and launch windborne spores that may infect the sunflower head.

Head rot might begin from wounds on the again of the sunflower heads, which may develop into websites of an infection.

Sclerotia germinate and infect sunflower roots after they come into contact with them in the course of the summer season. From the contaminated root, the fungus spreads to the taproot, the place it produces a canker on the base of the stem.

The plant finally wilts and dies as a result of this an infection stops it from absorbing water and vitamins. Root-to-root contact between sick crops can unfold the an infection to close by crops. The climate circumstances have little or no influence on the event of stalk rot.

establish the Sclerotinia ailments

Because the fungus releases spores throughout flowering, it infects the again of the top. When the circumstances are beneficial, the an infection worsens and the tissues develop into spongy, gentle brown, and delicate.

Finally, solely the fibrous strands in the back of the top and higher stalk stay attributable to this an infection, which additionally spreads into the creating head and down the stalk.

Quickly sufficient, the burden of the contaminated seed on the entrance of the top causes it to fall out of the top. Beneath the seed layer and surrounding the seeds, giant black sclerotia (small, black particles that resemble fowl droppings) type.

The contaminated plant will first exhibit abrupt wilting, particularly throughout grain fill, and a lightweight brown, moist spot on the base of the stalk will develop into noticeable. The tissue of the sunflower stem pith is white and resembles cotton.

It incorporates a mycelial development the place giant black sclerotia develop. As sunflower crops age, sclerotia might often be seen on the skin of the stalks.

At this stage of an infection, the stalk regularly breaks, revealing black sclerotia when it’s torn open. For the reason that plant is just not absorbing sufficient water and vitamins, heads don’t fill appropriately.

handle the illness

Sunflower head rot outbreaks have the potential to infest areas that had been beforehand sclerotinia-free or had low sclerotinia ranges.

Sunflowers and different delicate crops, which is perhaps replanted after a season of maize, are in danger from the diseased fields since sclerotia can persist for prolonged durations of time in contaminated soil.

Sunflowers shouldn’t be planted on contaminated land for at least 5 to eight years, in line with really useful observe. This will imply rising maize in a monoculture for not less than 5 rising seasons, relying on the manufacturing circumstances within the space.

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Extra so than head rot, rotation will reduce stem rot. Spores carried by the wind and carried in from the environment can nonetheless trigger head rot. Sclerotia which can be buried deeply are unable to provide apothecia.

It’s crucial to chorus from exposing these subterranean sclerotia in subsequent seasons, since this may increasingly result in the resurgence of the illness.

Sunflowers could also be threatened by these pests and fungi, however farmers can act preventatively by implementing administration methods to minimize the stress of each.

Sunflower producers can obtain extra ecologically pleasant and sustainable pest and illness management, bettering crop yields and product high quality whereas reducing long-term dependency on chemical pesticides, by incorporating built-in pest administration into their operations.

This technique not solely improves monetary efficiency but additionally fosters ecosystem well being and the welfare of each farmers and shoppers.

Adopting built-in pest administration is a essential step towards making certain sunflower agriculture’s sustained success within the face of evolving pest and illness challenges.

E mail Zunel van Eeden at [email protected]