Macadamia Farmers: Devastating Losses from Stink Bug Infestation

Macadamia farmers are facing significant challenges as stink bugs wreak havoc on their projected crop yields. These destructive insects, first discovered in Kenya in 1976, have the potential to cause substantial damage if left uncontrolled.

The Dominant Culprit: Southern Green Stink Bug

Among the various species of stink bugs, the southern green stink bug, scientifically known as Nezara viridula, is the primary culprit infesting nut trees. Equipped with piercing and sucking mouthparts in the form of a long beak-like structure called a rostrum, this bug poses a significant threat to macadamia trees. Its life cycle spans approximately 65-70 days, during which females can lay up to 260 eggs beneath the leaves.

Damage Caused by Stink Bugs

The destructive impact of stink bugs becomes apparent after the harvesting and processing stages. Stink bugs prefer to feed on mature nuts with green husks. By placing their stylet-like mouthparts on the nut husk and secreting saliva containing digestive enzymes, they soften the husk and gain access to the kernel. This feeding process results in discolored pits on the kernel’s surface and leads to premature nut drops. Furthermore, the infected kernels become susceptible to molds and fungi, causing additional losses and compromising the overall quality of the harvested nuts.

Effective Control Measures

To combat stink bug infestations, proactive measures should be taken. Since stink bugs require a primary food source other than macadamia nuts, it is crucial to eliminate host plants where they reproduce and develop. Weeding these host plants before land preparation is recommended. The following herbicides can be used during macadamia land preparation to clear all weeds:

1. CATAPULT 480 SL: A non-selective post-emergence herbicide effective against annual and perennial grasses, as well as broad-leaved weeds. It should be applied at a rate of 3.0 liters per hectare (300ml in 20L) to clear all weeds.

2. WEMBE 200 SL: Another non-selective post-emergence herbicide that effectively controls annual and perennial grasses, along with challenging weeds. Apply WEMBE 200 SL at a rate of 3.0 liters per hectare (300ml in 20L) during macadamia land preparation to eliminate all weeds.

Additionally, routine pesticide applications are highly recommended to reduce the stink bug population. For optimal results, it is advisable to use systemic and contact pesticides. Consider the following options:

1. LEXUS 247 SC: This pesticide, containing Thiamethoxam (141g/L) and Lambda-cyhalothrin (106g/L), offers both systemic and rapid knockdown control of stink bugs in macadamia trees. Thiamethoxam discourages pests by reducing the tree’s appeal and provides long-lasting control, while Lambda-cyhalothrin delivers immediate knockdown upon contact. LEXUS 247 SC also effectively targets Thrips, Aphids, Mealybugs, and Whiteflies. Apply at a rate of 200ml per hectare.

2. KINGCODE ELITE 50 EC: This pesticide, containing Lambda-cyhalothrin (15g/L) and Acetamiprid (35g/L), provides both contact and systemic control of stink bugs in macadamia trees. Lambda-cyhalothrin ensures immediate knockdown upon contact, while Acetamiprid offers long-lasting protection as it is absorbed by the plant and ingested by the pests. KINGCODE ELITE 50 EC is a broad-spectrum pesticide effective against Aphids, Thrips, Mealybugs, and Whiteflies. Apply at a rate of 400ml per hectare.

Conclusion

Macadamia farmers face significant losses from stink bug infestations if appropriate control measures are not implemented. By eliminating host plants and employing a combination of herbicides and targeted pesticides, farmers can effectively mitigate the damage caused by these destructive pests, safeguarding their projected production and ensuring the quality of their macadamia nuts.

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