Broad Mites are a very real hazard when propagating peppers. Of all the foods available for them to eat, peppers are the most nutritional for this pest. So heads-up. If you are going to grow your own supply of super hot capsicum like the Bhut Jolokia Ghost Pepper, or even the simplest sweet baby bell, you need to know how to identify and control this big problem this little bug can cause. Way back when I first started growing pepper plants, my peppers caught this bug instantaneously. I am growing in the upper central valley in my beautiful home nest of Costa Rica. I searched the internet images for the deformations and dried up initiating flowers I was experiencing. I found what I was looking for immediately. I was convinced the deformations were viral orientated. I was wrong. It wasn’t until I brought in an infected pepper plant to Lisela Moreira and Mauricio Montero Astuaat at the Centro de Investigación en Biología Celular y Molecular (CIBCM) of the Universidad de Costa Rica. They identified the culprit. I now know what was effecting my precious peppers so badly.

Broad Mite Polyphagotarsonemus latus

Polyphagotarsonemus latus was getting its Capsaicin from my peppers. P. latus is not visible with the naked eye. If you are very astute you ‘may’ be able to see it with the help of a magnifying glass. It is a minute herbivorous insect that infests a wide variety of plant crops including Solanaceae and Cucurbitaceae. This tiny mite causes severe symptoms and yield losses. Its destruction is mostly confined to new growths. The resulting damage is the curling of leaf margins, firmness of new leaves, necrosis of growing points, aborted buds, malformed fruits and growth inhibition.(1)

Broad Mites mostly feed on the underside of tender young foliage and floral structures such as flower buds. This retards growth and prevents flowers from fully developing. Leaf damage includes bronzing and distorted, the downward curling of leaves resulting from a phytotoxin secreted by feeding mites.

This toxin phytotoxin is still present even after the mite has been eliminated. So mite damage is a very serious problem

In peppers, young damaged leaves in the growing point curl up on the edge. Severely infested plants become stunted and may eventually die. Broad mites can be dispersed within a greenhouse by attaching themselves to whiteflies, greenhouse workers or equipment, or by movement of infested plant material into and throughout the greenhouse.

Life Cycle of the Broad Mite

The life cycle of P. latus passes through egg, larva, quiescent nymph and adult stages.(2) Copulation occurs immediately after the female has emerged from the quiescent nymph skin. Mated females produce both males and females, while unmated females produce only males. Eggs are laid singly on the underside of leaves often near the veins and depressions. The eggs will then hatch in 2 to 4 days . The larva becomes a protonymphs in about another 2 days. The protonymph, after under going a quiescent stage, develops into a deutonymph. At this stage sexes are determined. The deutonymph stage lasts for 1 to 3 days more. Next, the mite transforms itself into a quiescent pupal stage which sticks to the under side of the pepper leaves. The pupal stage lasts for about 2 days. Male longevity is 9-13 days and females live for 14-20 days.

Bilogical Control of Polyphagotarsonemus latus

Biological Control studies by the Zoology Department, Faculty of Science, Ain Shams University in Egypt evaluated seven pesticides against different stages of P. latus infesting pepper.

Their studies included the use of

  1. Abamectin (Vertemic 1.8% EC) (40 cm/100 L water),
  2. Liquid sulfur (Calcium polysulfide) (500 cm/100 L water),
  3. Botany gard (derived from the fungus Beauveria bassiana) (250 cm/100 L water),
  4. Canola oil (2% Erucic Acid Rapeseed oil) (300 cm/100 L water),
  5. Bioca (4.5% Matrine) (200 cm/100 L water),
  6. Orange oil (D-Limonene) (500 cm/100 L water) and
  7. Neemix (Azadirachtin) (75 cm/100 L water).
Abamectin is a compound derived from various laboratory broths fermented by the soil bacterium Streptomyces avermitilis. Abamectin is a natural fermentation product of this bacterium. A conscientious use of any chemical as a pesticide selected for agricultural use, depends on its environmental fate. Abamectin neither persists nor accumulates in the environment, rapidly degrades in water and its strong binding to soil limits its bio-availability. A few commercially available abamectin products, like AvidTM, ZephyrTM, VertimecTM or Agri-MekTM, are actually a mixture of 80% avermectin B1a and 20% avermectin B1b.

Adult Effectiveness of the Egypt Trial

The Ain Shams University studies final results showed that Abamectin, Liquid sulfur and Canola oil proved to be very effective insecticides against the adult P. latus. Orange oil, Beauveria bassiana and Matrine showed moderate efficiency and finally Azadirachtin caused slight effect. However, Rajasri et al. (1991) and Pena et al. (1996) showed that Beuvaria bassiana treated plants had greater percentage of adult P. latus mortality.

Egg Effectiveness of the Egypt Trial

Efficacies of the 7 trial compounds against P. latus eggs arranged in a descending order was as follows; Abamectin, Liquid sulfur, Canola oil, Orange oil, Beauveria bassiana, Azadirachtin and Matrine being 86.12%, 67.58%, 59.25%, 22.6%, 18.28%, 11.89% and 1.18%

Practical Field Application in Costa Rica

So with this study in hand I set off to save my peppers.

References

  1. Grinberg et al., 2005
  2. Vieira and Chiavegato (1998), Srinivasulu et al. (2002), Dhooria (2005)